From 0e87d18b016f4f08c95ed0c9e45d677ae0934bc9 Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Tue, 19 Nov 2019 09:26:46 +0900
Subject: [PATCH 01/18] Added a file that removes comments that start with #.

---
 package.json                                                | 2 ++
 .../decaff/__testfixtures__/remove-comment-sharp.input.js   | 6 ++++++
 .../decaff/__testfixtures__/remove-comment-sharp.output.js  | 6 ++++++
 scripts/decaff/__tests__/remove-comment-sharp.test.js       | 6 ++++++
 scripts/decaff/remove-comment-sharp.js                      | 4 ++++
 5 files changed, 24 insertions(+)
 create mode 100644 scripts/decaff/__testfixtures__/remove-comment-sharp.input.js
 create mode 100644 scripts/decaff/__testfixtures__/remove-comment-sharp.output.js
 create mode 100644 scripts/decaff/__tests__/remove-comment-sharp.test.js
 create mode 100644 scripts/decaff/remove-comment-sharp.js

diff --git a/package.json b/package.json
index 38a527786125..0797b06f1109 100644
--- a/package.json
+++ b/package.json
@@ -52,6 +52,7 @@
     "stop-only-all": "npm run stop-only -- --folder packages",
     "test": "echo '⚠️ This root monorepo is only for local development and new contributions. There are no tests.'",
     "test-debug-package": "node ./scripts/test-debug-package.js",
+    "test-jscodeshift": "jest ./scripts/decaff",
     "test-mocha": "mocha --reporter spec scripts/spec.js",
     "test-mocha-snapshot": "mocha scripts/mocha-snapshot-spec.js",
     "test-s3-api": "node -r ./packages/coffee/register -r ./packages/ts/register scripts/binary/s3-api-demo.ts",
@@ -133,6 +134,7 @@
     "husky": "2.4.1",
     "inquirer": "3.3.0",
     "inquirer-confirm": "2.0.3",
+    "jest": "24.9.0",
     "js-codemod": "cpojer/js-codemod#29dafed",
     "jscodemods": "cypress-io/jscodemods#01b546e",
     "jscodeshift": "0.6.3",
diff --git a/scripts/decaff/__testfixtures__/remove-comment-sharp.input.js b/scripts/decaff/__testfixtures__/remove-comment-sharp.input.js
new file mode 100644
index 000000000000..6a2f2a008f44
--- /dev/null
+++ b/scripts/decaff/__testfixtures__/remove-comment-sharp.input.js
@@ -0,0 +1,6 @@
+//# Testing this
+// eslint-disable-next-line
+console.log('it works') //# Test
+
+// This # should not be removed.
+/*# it's not wrong */
diff --git a/scripts/decaff/__testfixtures__/remove-comment-sharp.output.js b/scripts/decaff/__testfixtures__/remove-comment-sharp.output.js
new file mode 100644
index 000000000000..834260f7bfd0
--- /dev/null
+++ b/scripts/decaff/__testfixtures__/remove-comment-sharp.output.js
@@ -0,0 +1,6 @@
+// Testing this
+// eslint-disable-next-line
+console.log('it works') // Test
+
+// This # should not be removed.
+/*# it's not wrong */
diff --git a/scripts/decaff/__tests__/remove-comment-sharp.test.js b/scripts/decaff/__tests__/remove-comment-sharp.test.js
new file mode 100644
index 000000000000..352038332f49
--- /dev/null
+++ b/scripts/decaff/__tests__/remove-comment-sharp.test.js
@@ -0,0 +1,6 @@
+/* global jest */
+
+jest.autoMockOff()
+const defineTest = require('jscodeshift/dist/testUtils').defineTest
+
+defineTest(__dirname, 'remove-comment-sharp')
diff --git a/scripts/decaff/remove-comment-sharp.js b/scripts/decaff/remove-comment-sharp.js
new file mode 100644
index 000000000000..08273d5abd0f
--- /dev/null
+++ b/scripts/decaff/remove-comment-sharp.js
@@ -0,0 +1,4 @@
+// This file doesn't use AST because it makes things too complicated.
+module.exports = (fileInfo) => {
+  return fileInfo.source.replace(/\/\/#/g, '//')
+}

From 32791f920db2f6d6c9e11f00f3436b2f4732b2c0 Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Tue, 19 Nov 2019 11:10:06 +0900
Subject: [PATCH 02/18] Added .eslintrc to silence ts errors in codemods.

---
 scripts/decaff/.eslintrc.json | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 scripts/decaff/.eslintrc.json

diff --git a/scripts/decaff/.eslintrc.json b/scripts/decaff/.eslintrc.json
new file mode 100644
index 000000000000..db6ab5794049
--- /dev/null
+++ b/scripts/decaff/.eslintrc.json
@@ -0,0 +1,3 @@
+{
+  "parser": "espree"
+}

From 5387eea64855ec302e326af45293c0d2b26e2fa3 Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Tue, 19 Nov 2019 11:10:25 +0900
Subject: [PATCH 03/18] Convert switch (false) to if-else.

---
 .../__testfixtures__/switch-false.input.js    | 28 ++++++++
 .../__testfixtures__/switch-false.output.js   | 22 ++++++
 scripts/decaff/__tests__/switch-false.test.js |  6 ++
 scripts/decaff/switch-false.js                | 67 +++++++++++++++++++
 4 files changed, 123 insertions(+)
 create mode 100644 scripts/decaff/__testfixtures__/switch-false.input.js
 create mode 100644 scripts/decaff/__testfixtures__/switch-false.output.js
 create mode 100644 scripts/decaff/__tests__/switch-false.test.js
 create mode 100644 scripts/decaff/switch-false.js

diff --git a/scripts/decaff/__testfixtures__/switch-false.input.js b/scripts/decaff/__testfixtures__/switch-false.input.js
new file mode 100644
index 000000000000..1a635541b867
--- /dev/null
+++ b/scripts/decaff/__testfixtures__/switch-false.input.js
@@ -0,0 +1,28 @@
+/* global a, b, c, findThings, isBad, isAwesome, hi */
+
+function f () {
+  switch (false) {
+    case !a.subject(a):
+      let x = 30
+
+      b.doSomething(x)
+      break
+    case c.isGood:
+      c.checkThisOut()
+      findThings()
+      break
+    case isBad:
+      c.neverCheck()
+      break
+    case !isAwesome:
+      a.subject(a)
+      break
+    case hi:
+      return 3
+    default:
+      b.goToNext()
+      break
+  }
+}
+
+f()
diff --git a/scripts/decaff/__testfixtures__/switch-false.output.js b/scripts/decaff/__testfixtures__/switch-false.output.js
new file mode 100644
index 000000000000..1c0d0ebb40cb
--- /dev/null
+++ b/scripts/decaff/__testfixtures__/switch-false.output.js
@@ -0,0 +1,22 @@
+/* global a, b, c, findThings, isBad, isAwesome, hi */
+
+function f () {
+  if (a.subject(a)) {
+    let x = 30
+
+    b.doSomething(x)
+  } else if (!c.isGood) {
+    c.checkThisOut()
+    findThings()
+  } else if (!isBad) {
+    c.neverCheck()
+  } else if (isAwesome) {
+    a.subject(a)
+  } else if (!hi) {
+    return 3
+  } else {
+    b.goToNext()
+  }
+}
+
+f()
diff --git a/scripts/decaff/__tests__/switch-false.test.js b/scripts/decaff/__tests__/switch-false.test.js
new file mode 100644
index 000000000000..86ebfccf5ec1
--- /dev/null
+++ b/scripts/decaff/__tests__/switch-false.test.js
@@ -0,0 +1,6 @@
+/* global jest */
+
+jest.autoMockOff()
+const defineTest = require('jscodeshift/dist/testUtils').defineTest
+
+defineTest(__dirname, 'switch-false')
diff --git a/scripts/decaff/switch-false.js b/scripts/decaff/switch-false.js
new file mode 100644
index 000000000000..9bb2e0077449
--- /dev/null
+++ b/scripts/decaff/switch-false.js
@@ -0,0 +1,67 @@
+module.exports = (fileInfo, api) => {
+  const j = api.jscodeshift
+
+  return j(fileInfo.source)
+  .find(j.SwitchStatement, {
+    discriminant: {
+      type: 'Literal',
+      value: false,
+    },
+  })
+  .replaceWith((nodePath) => {
+    const { node } = nodePath
+
+    const cases = node.cases.map((c) => {
+      const { test, consequent } = c
+
+      return {
+        test: generateTest(j, test),
+        content: generateContent(j, consequent),
+      }
+    })
+
+    const ifStatement = generateIfStatement(j, cases)
+
+    ifStatement.comments = node.comments
+
+    return ifStatement
+  })
+  .toSource()
+}
+
+function generateTest (j, test) {
+  if (test) {
+    if (test.type === 'UnaryExpression') {
+      return test.argument
+    }
+
+    return j.unaryExpression('!', test)
+  }
+
+  return null
+}
+
+function generateContent (j, consequent) {
+  return j.blockStatement(consequent.filter((c) => c.type !== 'BreakStatement'))
+}
+
+function generateIfStatement (j, cases) {
+  const nonDefaultCases = cases.filter((c) => c.test !== null)
+  const defaultCase = cases.filter((c) => c.test === null)[0]
+
+  let ifStatement = null
+
+  if (defaultCase) {
+    ifStatement = defaultCase.content
+  }
+
+  nonDefaultCases.reverse().forEach((c) => {
+    ifStatement = j.ifStatement(
+      c.test,
+      c.content,
+      ifStatement
+    )
+  })
+
+  return ifStatement
+}

From 5c3c623f056756e1214826a059a0e19d4587d29a Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Tue, 19 Nov 2019 11:37:08 +0900
Subject: [PATCH 04/18] Add disable-eslint no-empty by default after empty
 catch.

---
 .../__testfixtures__/empty-catch.input.js     |  7 +++++
 .../__testfixtures__/empty-catch.output.js    |  7 +++++
 scripts/decaff/__tests__/empty-catch.test.js  |  6 ++++
 scripts/decaff/empty-catch.js                 | 28 +++++++++++++++++++
 4 files changed, 48 insertions(+)
 create mode 100644 scripts/decaff/__testfixtures__/empty-catch.input.js
 create mode 100644 scripts/decaff/__testfixtures__/empty-catch.output.js
 create mode 100644 scripts/decaff/__tests__/empty-catch.test.js
 create mode 100644 scripts/decaff/empty-catch.js

diff --git a/scripts/decaff/__testfixtures__/empty-catch.input.js b/scripts/decaff/__testfixtures__/empty-catch.input.js
new file mode 100644
index 000000000000..ea887d4b034c
--- /dev/null
+++ b/scripts/decaff/__testfixtures__/empty-catch.input.js
@@ -0,0 +1,7 @@
+try {
+  // do something
+} catch (e) {}
+
+try {
+  // do something
+} finally {}
diff --git a/scripts/decaff/__testfixtures__/empty-catch.output.js b/scripts/decaff/__testfixtures__/empty-catch.output.js
new file mode 100644
index 000000000000..e7ef9ff68c38
--- /dev/null
+++ b/scripts/decaff/__testfixtures__/empty-catch.output.js
@@ -0,0 +1,7 @@
+try {
+  // do something
+} catch (e) {} // eslint-disable-line no-empty
+
+try {
+  // do something
+} finally {}
diff --git a/scripts/decaff/__tests__/empty-catch.test.js b/scripts/decaff/__tests__/empty-catch.test.js
new file mode 100644
index 000000000000..dbd86f548880
--- /dev/null
+++ b/scripts/decaff/__tests__/empty-catch.test.js
@@ -0,0 +1,6 @@
+/* global jest */
+
+jest.autoMockOff()
+const defineTest = require('jscodeshift/dist/testUtils').defineTest
+
+defineTest(__dirname, 'empty-catch')
diff --git a/scripts/decaff/empty-catch.js b/scripts/decaff/empty-catch.js
new file mode 100644
index 000000000000..815b8395859b
--- /dev/null
+++ b/scripts/decaff/empty-catch.js
@@ -0,0 +1,28 @@
+module.exports = (fileInfo, api) => {
+  const j = api.jscodeshift
+
+  const source = j(fileInfo.source)
+  .find(j.TryStatement)
+  .replaceWith((nodePath) => {
+    const { node } = nodePath
+
+    // Add trailing eslint-disable-line for empty catch block
+    if (node.handler && node.handler.body.body.length === 0) {
+      node.handler.body.comments = [
+        {
+          type: 'Line',
+          value: ' eslint-disable-line no-empty',
+          leading: false,
+          trailing: true,
+        },
+      ]
+    }
+
+    return node
+  })
+  .toSource()
+
+  // Generated source above creates {}// eslint-disable-line block.
+  // So, add a space with replace
+  return source.replace(/\{\}\/\/ eslint-disable-line/g, '{} // eslint-disable-line')
+}

From e85c6455c0a12a2711293829db494694d9e9c765 Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Tue, 19 Nov 2019 12:13:38 +0900
Subject: [PATCH 05/18] Reserve comments when converting switch-case.

---
 .../__testfixtures__/switch-false.input.js    |  2 ++
 .../__testfixtures__/switch-false.output.js   | 14 +++++-----
 scripts/decaff/switch-false.js                | 27 ++++++++++++++++---
 3 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/scripts/decaff/__testfixtures__/switch-false.input.js b/scripts/decaff/__testfixtures__/switch-false.input.js
index 1a635541b867..877f73801374 100644
--- a/scripts/decaff/__testfixtures__/switch-false.input.js
+++ b/scripts/decaff/__testfixtures__/switch-false.input.js
@@ -2,11 +2,13 @@
 
 function f () {
   switch (false) {
+    // Comment should be reserved
     case !a.subject(a):
       let x = 30
 
       b.doSomething(x)
       break
+    // Comment should be reserved 2
     case c.isGood:
       c.checkThisOut()
       findThings()
diff --git a/scripts/decaff/__testfixtures__/switch-false.output.js b/scripts/decaff/__testfixtures__/switch-false.output.js
index 1c0d0ebb40cb..07dacb8e264a 100644
--- a/scripts/decaff/__testfixtures__/switch-false.output.js
+++ b/scripts/decaff/__testfixtures__/switch-false.output.js
@@ -2,20 +2,22 @@
 
 function f () {
   if (a.subject(a)) {
-    let x = 30
+    // Comment should be reserved
+    let x = 30;
 
     b.doSomething(x)
   } else if (!c.isGood) {
-    c.checkThisOut()
+    // Comment should be reserved 2
+    c.checkThisOut();
     findThings()
   } else if (!isBad) {
-    c.neverCheck()
+    c.neverCheck();
   } else if (isAwesome) {
-    a.subject(a)
+    a.subject(a);
   } else if (!hi) {
-    return 3
+    return 3;
   } else {
-    b.goToNext()
+    b.goToNext();
   }
 }
 
diff --git a/scripts/decaff/switch-false.js b/scripts/decaff/switch-false.js
index 9bb2e0077449..9e0ed3a12ba1 100644
--- a/scripts/decaff/switch-false.js
+++ b/scripts/decaff/switch-false.js
@@ -12,11 +12,12 @@ module.exports = (fileInfo, api) => {
     const { node } = nodePath
 
     const cases = node.cases.map((c) => {
-      const { test, consequent } = c
+      const { test, consequent, comments } = c
 
       return {
         test: generateTest(j, test),
         content: generateContent(j, consequent),
+        comments,
       }
     })
 
@@ -52,16 +53,36 @@ function generateIfStatement (j, cases) {
   let ifStatement = null
 
   if (defaultCase) {
-    ifStatement = defaultCase.content
+    const content = addComment(defaultCase.content, defaultCase.comments)
+
+    ifStatement = content
   }
 
   nonDefaultCases.reverse().forEach((c) => {
+    const content = addComment(c.content, c.comments)
+
     ifStatement = j.ifStatement(
       c.test,
-      c.content,
+      content,
       ifStatement
     )
   })
 
   return ifStatement
 }
+
+function addComment (content, comments) {
+  if (content.body.length > 0) {
+    content.body[0].comments = [...(comments || []), ...(content.comments || [])]
+  } else {
+    content.comments = (comments || []).map((co) => {
+      return {
+        ...co,
+        leading: false,
+        trailing: false,
+      }
+    })
+  }
+
+  return content
+}

From 4fa499e1f456221edc196975ebdd028478b3c35f Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Tue, 19 Nov 2019 12:14:27 +0900
Subject: [PATCH 06/18] Added new codemods to bulk-decaffeinate.

---
 bulk-decaffeinate.config.js | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/bulk-decaffeinate.config.js b/bulk-decaffeinate.config.js
index 7f81e1d7f506..f7c2c068dd61 100644
--- a/bulk-decaffeinate.config.js
+++ b/bulk-decaffeinate.config.js
@@ -13,5 +13,8 @@ module.exports = {
     path.resolve('node_modules', 'jscodemods', 'decaffeinate', 'fix-multi-assign-class-export.js'),
     path.resolve('node_modules', 'jscodemods', 'decaffeinate', 'fix-implicit-return-assignment.js'),
     path.resolve('node_modules', 'jscodemods', 'decaffeinate', 'fix-existential-conditional-assignment.js'),
+    './scripts/decaff/remove-comment-sharp.js',
+    './scripts/decaff/switch-false.js',
+    './scripts/decaff/empty-catch.js',
   ],
 }

From 66fc913dec9b23609000b2e78941aa4f06a37271 Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Tue, 19 Nov 2019 12:42:23 +0900
Subject: [PATCH 07/18] Preserve comments.

---
 .../decaff/__testfixtures__/switch-false.input.js  |  9 +++++++--
 .../decaff/__testfixtures__/switch-false.output.js | 11 +++++++----
 scripts/decaff/switch-false.js                     | 14 ++++++++++++--
 3 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/scripts/decaff/__testfixtures__/switch-false.input.js b/scripts/decaff/__testfixtures__/switch-false.input.js
index 877f73801374..16247d4f06dc 100644
--- a/scripts/decaff/__testfixtures__/switch-false.input.js
+++ b/scripts/decaff/__testfixtures__/switch-false.input.js
@@ -1,4 +1,4 @@
-/* global a, b, c, findThings, isBad, isAwesome, hi */
+/* global a, b, c, findThings, isBad, isAwesome, hi, you */
 
 function f () {
   switch (false) {
@@ -8,7 +8,8 @@ function f () {
 
       b.doSomething(x)
       break
-    // Comment should be reserved 2
+    // Multi line comment
+    // should be reserved
     case c.isGood:
       c.checkThisOut()
       findThings()
@@ -20,7 +21,11 @@ function f () {
       a.subject(a)
       break
     case hi:
+      // This should be reserved, too
       return 3
+    case you:
+      // This comment is preserved
+      break
     default:
       b.goToNext()
       break
diff --git a/scripts/decaff/__testfixtures__/switch-false.output.js b/scripts/decaff/__testfixtures__/switch-false.output.js
index 07dacb8e264a..c787b2d3da64 100644
--- a/scripts/decaff/__testfixtures__/switch-false.output.js
+++ b/scripts/decaff/__testfixtures__/switch-false.output.js
@@ -1,4 +1,4 @@
-/* global a, b, c, findThings, isBad, isAwesome, hi */
+/* global a, b, c, findThings, isBad, isAwesome, hi, you */
 
 function f () {
   if (a.subject(a)) {
@@ -7,7 +7,8 @@ function f () {
 
     b.doSomething(x)
   } else if (!c.isGood) {
-    // Comment should be reserved 2
+    // Multi line comment
+    // should be reserved
     c.checkThisOut();
     findThings()
   } else if (!isBad) {
@@ -15,8 +16,10 @@ function f () {
   } else if (isAwesome) {
     a.subject(a);
   } else if (!hi) {
-    return 3;
-  } else {
+    // This should be reserved, too
+    return 3
+  } else if (!you) // This comment is preserved
+  {} else {
     b.goToNext();
   }
 }
diff --git a/scripts/decaff/switch-false.js b/scripts/decaff/switch-false.js
index 9e0ed3a12ba1..850a8fe90495 100644
--- a/scripts/decaff/switch-false.js
+++ b/scripts/decaff/switch-false.js
@@ -43,6 +43,14 @@ function generateTest (j, test) {
 }
 
 function generateContent (j, consequent) {
+  if (consequent.length === 1 && consequent[0].type === 'BreakStatement') {
+    const block = j.blockStatement([])
+
+    block.comments = consequent[0].comments
+
+    return block
+  }
+
   return j.blockStatement(consequent.filter((c) => c.type !== 'BreakStatement'))
 }
 
@@ -73,15 +81,17 @@ function generateIfStatement (j, cases) {
 
 function addComment (content, comments) {
   if (content.body.length > 0) {
-    content.body[0].comments = [...(comments || []), ...(content.comments || [])]
+    content.body[0].comments = [...(comments || []), ...(content.body[0].comments || [])]
   } else {
-    content.comments = (comments || []).map((co) => {
+    const newComments = (comments || []).map((co) => {
       return {
         ...co,
         leading: false,
         trailing: false,
       }
     })
+
+    content.comments = [...newComments, ...(content.comments || [])]
   }
 
   return content

From 6e2da0c1ca0ba176aa9d5b7f2412fced21d9c72f Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Tue, 19 Nov 2019 15:05:06 +0900
Subject: [PATCH 08/18] Ignored lint rules for test fixtures.

---
 scripts/decaff/__testfixtures__/.eslintrc.json | 9 +++++++++
 1 file changed, 9 insertions(+)
 create mode 100644 scripts/decaff/__testfixtures__/.eslintrc.json

diff --git a/scripts/decaff/__testfixtures__/.eslintrc.json b/scripts/decaff/__testfixtures__/.eslintrc.json
new file mode 100644
index 000000000000..bbf3e6188a43
--- /dev/null
+++ b/scripts/decaff/__testfixtures__/.eslintrc.json
@@ -0,0 +1,9 @@
+{
+  "parser": "espree",
+  "rules": {
+    "no-empty": "off",
+    "semi": "off",
+    "brace-style": "off",
+    "no-case-declarations": "off"
+  }
+}

From b29eab44a5b3c8bac357682528c6b30fd3358a1e Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Wed, 20 Nov 2019 10:02:21 +0900
Subject: [PATCH 09/18] Move comments between arrow and block to the top.

---
 .../__testfixtures__/arrow-comment.input.js   | 10 +++++++
 .../__testfixtures__/arrow-comment.output.js  | 10 +++++++
 .../decaff/__tests__/arrow-comment.test.js    |  6 +++++
 scripts/decaff/arrow-comment.js               | 27 +++++++++++++++++++
 4 files changed, 53 insertions(+)
 create mode 100644 scripts/decaff/__testfixtures__/arrow-comment.input.js
 create mode 100644 scripts/decaff/__testfixtures__/arrow-comment.output.js
 create mode 100644 scripts/decaff/__tests__/arrow-comment.test.js
 create mode 100644 scripts/decaff/arrow-comment.js

diff --git a/scripts/decaff/__testfixtures__/arrow-comment.input.js b/scripts/decaff/__testfixtures__/arrow-comment.input.js
new file mode 100644
index 000000000000..357c42d5825e
--- /dev/null
+++ b/scripts/decaff/__testfixtures__/arrow-comment.input.js
@@ -0,0 +1,10 @@
+// Original comment
+const func = (a, b) =>
+// Multiline comment
+// is here
+{
+  a.works()
+  b.check.thisOut()
+}
+
+func()
diff --git a/scripts/decaff/__testfixtures__/arrow-comment.output.js b/scripts/decaff/__testfixtures__/arrow-comment.output.js
new file mode 100644
index 000000000000..1593e89d37d5
--- /dev/null
+++ b/scripts/decaff/__testfixtures__/arrow-comment.output.js
@@ -0,0 +1,10 @@
+// Original comment
+// Multiline comment
+// is here
+const func = (a, b) =>
+{
+  a.works()
+  b.check.thisOut()
+};
+
+func()
diff --git a/scripts/decaff/__tests__/arrow-comment.test.js b/scripts/decaff/__tests__/arrow-comment.test.js
new file mode 100644
index 000000000000..5d5eaa25577f
--- /dev/null
+++ b/scripts/decaff/__tests__/arrow-comment.test.js
@@ -0,0 +1,6 @@
+/* global jest */
+
+jest.autoMockOff()
+const defineTest = require('jscodeshift/dist/testUtils').defineTest
+
+defineTest(__dirname, 'arrow-comment')
diff --git a/scripts/decaff/arrow-comment.js b/scripts/decaff/arrow-comment.js
new file mode 100644
index 000000000000..044870f9b0e1
--- /dev/null
+++ b/scripts/decaff/arrow-comment.js
@@ -0,0 +1,27 @@
+module.exports = (fileInfo, api) => {
+  const j = api.jscodeshift
+
+  return j(fileInfo.source)
+  .find(j.VariableDeclaration, {
+    declarations: [{
+      type: 'VariableDeclarator',
+      init: {
+        type: 'ArrowFunctionExpression',
+        body: {
+          type: 'BlockStatement',
+        },
+      },
+    }],
+  })
+  .replaceWith((nodePath) => {
+    const { node } = nodePath
+
+    if (node.declarations[0].init.body.comments.length > 0) {
+      node.comments = [...node.comments, ...node.declarations[0].init.body.comments]
+      node.declarations[0].init.body.comments = null
+    }
+
+    return node
+  })
+  .toSource()
+}

From 687bc2bf1d18f2a5961463e23f45df40a0ebea9c Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Wed, 20 Nov 2019 10:04:35 +0900
Subject: [PATCH 10/18] Merged tests into one file.

---
 scripts/decaff/__tests__/arrow-comment.test.js              | 6 ------
 .../{remove-comment-sharp.test.js => decaff.test.js}        | 3 +++
 scripts/decaff/__tests__/empty-catch.test.js                | 6 ------
 scripts/decaff/__tests__/switch-false.test.js               | 6 ------
 4 files changed, 3 insertions(+), 18 deletions(-)
 delete mode 100644 scripts/decaff/__tests__/arrow-comment.test.js
 rename scripts/decaff/__tests__/{remove-comment-sharp.test.js => decaff.test.js} (57%)
 delete mode 100644 scripts/decaff/__tests__/empty-catch.test.js
 delete mode 100644 scripts/decaff/__tests__/switch-false.test.js

diff --git a/scripts/decaff/__tests__/arrow-comment.test.js b/scripts/decaff/__tests__/arrow-comment.test.js
deleted file mode 100644
index 5d5eaa25577f..000000000000
--- a/scripts/decaff/__tests__/arrow-comment.test.js
+++ /dev/null
@@ -1,6 +0,0 @@
-/* global jest */
-
-jest.autoMockOff()
-const defineTest = require('jscodeshift/dist/testUtils').defineTest
-
-defineTest(__dirname, 'arrow-comment')
diff --git a/scripts/decaff/__tests__/remove-comment-sharp.test.js b/scripts/decaff/__tests__/decaff.test.js
similarity index 57%
rename from scripts/decaff/__tests__/remove-comment-sharp.test.js
rename to scripts/decaff/__tests__/decaff.test.js
index 352038332f49..6382628fa29a 100644
--- a/scripts/decaff/__tests__/remove-comment-sharp.test.js
+++ b/scripts/decaff/__tests__/decaff.test.js
@@ -3,4 +3,7 @@
 jest.autoMockOff()
 const defineTest = require('jscodeshift/dist/testUtils').defineTest
 
+defineTest(__dirname, 'switch-false')
+defineTest(__dirname, 'empty-catch')
 defineTest(__dirname, 'remove-comment-sharp')
+defineTest(__dirname, 'arrow-comment')
diff --git a/scripts/decaff/__tests__/empty-catch.test.js b/scripts/decaff/__tests__/empty-catch.test.js
deleted file mode 100644
index dbd86f548880..000000000000
--- a/scripts/decaff/__tests__/empty-catch.test.js
+++ /dev/null
@@ -1,6 +0,0 @@
-/* global jest */
-
-jest.autoMockOff()
-const defineTest = require('jscodeshift/dist/testUtils').defineTest
-
-defineTest(__dirname, 'empty-catch')
diff --git a/scripts/decaff/__tests__/switch-false.test.js b/scripts/decaff/__tests__/switch-false.test.js
deleted file mode 100644
index 86ebfccf5ec1..000000000000
--- a/scripts/decaff/__tests__/switch-false.test.js
+++ /dev/null
@@ -1,6 +0,0 @@
-/* global jest */
-
-jest.autoMockOff()
-const defineTest = require('jscodeshift/dist/testUtils').defineTest
-
-defineTest(__dirname, 'switch-false')

From 263f6a8cd742b2255e343fcb6365a20affc3b444 Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Wed, 20 Nov 2019 10:38:23 +0900
Subject: [PATCH 11/18] Turned off no-undef for test fixtures.

---
 scripts/decaff/__testfixtures__/.eslintrc.json         | 1 +
 scripts/decaff/__testfixtures__/switch-false.input.js  | 2 --
 scripts/decaff/__testfixtures__/switch-false.output.js | 2 --
 3 files changed, 1 insertion(+), 4 deletions(-)

diff --git a/scripts/decaff/__testfixtures__/.eslintrc.json b/scripts/decaff/__testfixtures__/.eslintrc.json
index bbf3e6188a43..311d18860155 100644
--- a/scripts/decaff/__testfixtures__/.eslintrc.json
+++ b/scripts/decaff/__testfixtures__/.eslintrc.json
@@ -2,6 +2,7 @@
   "parser": "espree",
   "rules": {
     "no-empty": "off",
+    "no-undef": "off",
     "semi": "off",
     "brace-style": "off",
     "no-case-declarations": "off"
diff --git a/scripts/decaff/__testfixtures__/switch-false.input.js b/scripts/decaff/__testfixtures__/switch-false.input.js
index 16247d4f06dc..78af2d53df24 100644
--- a/scripts/decaff/__testfixtures__/switch-false.input.js
+++ b/scripts/decaff/__testfixtures__/switch-false.input.js
@@ -1,5 +1,3 @@
-/* global a, b, c, findThings, isBad, isAwesome, hi, you */
-
 function f () {
   switch (false) {
     // Comment should be reserved
diff --git a/scripts/decaff/__testfixtures__/switch-false.output.js b/scripts/decaff/__testfixtures__/switch-false.output.js
index c787b2d3da64..cb82f14828a0 100644
--- a/scripts/decaff/__testfixtures__/switch-false.output.js
+++ b/scripts/decaff/__testfixtures__/switch-false.output.js
@@ -1,5 +1,3 @@
-/* global a, b, c, findThings, isBad, isAwesome, hi, you */
-
 function f () {
   if (a.subject(a)) {
     // Comment should be reserved

From a90f724408f1c0d642af10a86332fa348db2dc7a Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Wed, 20 Nov 2019 10:56:24 +0900
Subject: [PATCH 12/18] No-cond-assign

---
 .../decaff/__testfixtures__/.eslintrc.json    |  1 +
 .../__testfixtures__/no-cond-assign.input.js  |  6 ++++
 .../__testfixtures__/no-cond-assign.output.js |  8 +++++
 scripts/decaff/__tests__/decaff.test.js       |  1 +
 scripts/decaff/no-cond-assign.js              | 29 +++++++++++++++++++
 5 files changed, 45 insertions(+)
 create mode 100644 scripts/decaff/__testfixtures__/no-cond-assign.input.js
 create mode 100644 scripts/decaff/__testfixtures__/no-cond-assign.output.js
 create mode 100644 scripts/decaff/no-cond-assign.js

diff --git a/scripts/decaff/__testfixtures__/.eslintrc.json b/scripts/decaff/__testfixtures__/.eslintrc.json
index 311d18860155..21e7f159b82c 100644
--- a/scripts/decaff/__testfixtures__/.eslintrc.json
+++ b/scripts/decaff/__testfixtures__/.eslintrc.json
@@ -3,6 +3,7 @@
   "rules": {
     "no-empty": "off",
     "no-undef": "off",
+    "no-cond-assign": "off",
     "semi": "off",
     "brace-style": "off",
     "no-case-declarations": "off"
diff --git a/scripts/decaff/__testfixtures__/no-cond-assign.input.js b/scripts/decaff/__testfixtures__/no-cond-assign.input.js
new file mode 100644
index 000000000000..896e62036218
--- /dev/null
+++ b/scripts/decaff/__testfixtures__/no-cond-assign.input.js
@@ -0,0 +1,6 @@
+let a
+
+// Comment
+if (a = c()) {
+  a.fix()
+}
diff --git a/scripts/decaff/__testfixtures__/no-cond-assign.output.js b/scripts/decaff/__testfixtures__/no-cond-assign.output.js
new file mode 100644
index 000000000000..3541fbd343a2
--- /dev/null
+++ b/scripts/decaff/__testfixtures__/no-cond-assign.output.js
@@ -0,0 +1,8 @@
+let a
+
+// Comment
+a = c();
+
+if (a) {
+  a.fix()
+}
diff --git a/scripts/decaff/__tests__/decaff.test.js b/scripts/decaff/__tests__/decaff.test.js
index 6382628fa29a..4921d9b52b37 100644
--- a/scripts/decaff/__tests__/decaff.test.js
+++ b/scripts/decaff/__tests__/decaff.test.js
@@ -7,3 +7,4 @@ defineTest(__dirname, 'switch-false')
 defineTest(__dirname, 'empty-catch')
 defineTest(__dirname, 'remove-comment-sharp')
 defineTest(__dirname, 'arrow-comment')
+defineTest(__dirname, 'no-cond-assign')
diff --git a/scripts/decaff/no-cond-assign.js b/scripts/decaff/no-cond-assign.js
new file mode 100644
index 000000000000..3c74a3b1f89d
--- /dev/null
+++ b/scripts/decaff/no-cond-assign.js
@@ -0,0 +1,29 @@
+module.exports = (fileInfo, api) => {
+  const j = api.jscodeshift
+
+  return j(fileInfo.source)
+  .find(j.IfStatement, {
+    test: {
+      type: 'AssignmentExpression',
+    },
+  })
+  .replaceWith((nodePath) => {
+    const { node } = nodePath
+
+    const assign = j.expressionStatement(node.test)
+
+    assign.comments = node.comments
+
+    const ifStatement = j.ifStatement(
+      node.test.left,
+      node.consequent,
+      node.alternate
+    )
+
+    return [
+      assign,
+      ifStatement,
+    ]
+  })
+  .toSource()
+}

From ef0c0f8d92540bd71f3c688e48ce219ffda65275 Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Wed, 20 Nov 2019 10:59:11 +0900
Subject: [PATCH 13/18] Added jscodemods to decaff config.

---
 bulk-decaffeinate.config.js | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/bulk-decaffeinate.config.js b/bulk-decaffeinate.config.js
index f7c2c068dd61..ed68498132ef 100644
--- a/bulk-decaffeinate.config.js
+++ b/bulk-decaffeinate.config.js
@@ -16,5 +16,7 @@ module.exports = {
     './scripts/decaff/remove-comment-sharp.js',
     './scripts/decaff/switch-false.js',
     './scripts/decaff/empty-catch.js',
+    './scripts/decaff/no-cond-assing.js',
+    './scripts/decaff/arrow-comment.js',
   ],
 }

From 7cccd9c2e7779e4f26a2e7c826abd4df1a30be21 Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Thu, 21 Nov 2019 09:01:07 +0900
Subject: [PATCH 14/18] Fixed typo.

---
 bulk-decaffeinate.config.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/bulk-decaffeinate.config.js b/bulk-decaffeinate.config.js
index ed68498132ef..e7af5f254a2d 100644
--- a/bulk-decaffeinate.config.js
+++ b/bulk-decaffeinate.config.js
@@ -16,7 +16,7 @@ module.exports = {
     './scripts/decaff/remove-comment-sharp.js',
     './scripts/decaff/switch-false.js',
     './scripts/decaff/empty-catch.js',
-    './scripts/decaff/no-cond-assing.js',
+    './scripts/decaff/no-cond-assign.js',
     './scripts/decaff/arrow-comment.js',
   ],
 }

From 1f5ae33bbd60e2daf690a331f0c8e37a2c5fef53 Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Wed, 27 Nov 2019 15:50:03 +0900
Subject: [PATCH 15/18] Make CI test codemods

---
 circle.yml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/circle.yml b/circle.yml
index 951cfab046bd..de86112a72f3 100644
--- a/circle.yml
+++ b/circle.yml
@@ -290,6 +290,8 @@ jobs:
       - run: npm run test-mocha-snapshot
       # make sure packages with TypeScript can be transpiled to JS
       - run: npm run all build-js
+      # test codemods
+      - run: npm run test-jscodeshift
       # run unit tests from individual packages
       - run: npm run all test -- --package cli
       - run: npm run all test -- --package electron

From 71c4fe25240e321d5b20302d801aacfc9822f832 Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Mon, 2 Dec 2019 18:19:46 +0900
Subject: [PATCH 16/18] Added test-no-return.

---
 bulk-decaffeinate.config.js                   |  1 +
 .../__testfixtures__/test-no-return.input.js  | 24 +++++++++
 .../__testfixtures__/test-no-return.output.js | 24 +++++++++
 scripts/decaff/__tests__/decaff.test.js       |  1 +
 scripts/decaff/test-no-return.js              | 51 +++++++++++++++++++
 5 files changed, 101 insertions(+)
 create mode 100644 scripts/decaff/__testfixtures__/test-no-return.input.js
 create mode 100644 scripts/decaff/__testfixtures__/test-no-return.output.js
 create mode 100644 scripts/decaff/test-no-return.js

diff --git a/bulk-decaffeinate.config.js b/bulk-decaffeinate.config.js
index e7af5f254a2d..8120ef9cf4b0 100644
--- a/bulk-decaffeinate.config.js
+++ b/bulk-decaffeinate.config.js
@@ -18,5 +18,6 @@ module.exports = {
     './scripts/decaff/empty-catch.js',
     './scripts/decaff/no-cond-assign.js',
     './scripts/decaff/arrow-comment.js',
+    './scripts/decaff/test-no-return.js',
   ],
 }
diff --git a/scripts/decaff/__testfixtures__/test-no-return.input.js b/scripts/decaff/__testfixtures__/test-no-return.input.js
new file mode 100644
index 000000000000..07c28501686f
--- /dev/null
+++ b/scripts/decaff/__testfixtures__/test-no-return.input.js
@@ -0,0 +1,24 @@
+context('a', function () {
+  beforeEach(() => {
+    doSomething()
+
+    return settings.write('something')
+  })
+
+  afterEach(() => {
+    return settings.reset()
+  })
+
+  it('test 1', function () {
+    cy.visit('hi/world')
+
+    return cy.click('abc')
+  })
+
+  it('test 2', () => {
+    return this.project.saveState()
+    .then((state) => {
+      expect(state).to.deep.eq({})
+    })
+  })
+})
diff --git a/scripts/decaff/__testfixtures__/test-no-return.output.js b/scripts/decaff/__testfixtures__/test-no-return.output.js
new file mode 100644
index 000000000000..e157967c67b0
--- /dev/null
+++ b/scripts/decaff/__testfixtures__/test-no-return.output.js
@@ -0,0 +1,24 @@
+context('a', function () {
+  beforeEach(() => {
+    doSomething()
+
+    settings.write('something');
+  })
+
+  afterEach(() => {
+    settings.reset();
+  })
+
+  it('test 1', function () {
+    cy.visit('hi/world')
+
+    cy.click('abc');
+  })
+
+  it('test 2', () => {
+    this.project.saveState()
+    .then((state) => {
+      expect(state).to.deep.eq({})
+    });
+  })
+})
diff --git a/scripts/decaff/__tests__/decaff.test.js b/scripts/decaff/__tests__/decaff.test.js
index 4921d9b52b37..c613a1a0582b 100644
--- a/scripts/decaff/__tests__/decaff.test.js
+++ b/scripts/decaff/__tests__/decaff.test.js
@@ -8,3 +8,4 @@ defineTest(__dirname, 'empty-catch')
 defineTest(__dirname, 'remove-comment-sharp')
 defineTest(__dirname, 'arrow-comment')
 defineTest(__dirname, 'no-cond-assign')
+defineTest(__dirname, 'test-no-return')
diff --git a/scripts/decaff/test-no-return.js b/scripts/decaff/test-no-return.js
new file mode 100644
index 000000000000..f3d39398ddbc
--- /dev/null
+++ b/scripts/decaff/test-no-return.js
@@ -0,0 +1,51 @@
+module.exports = (fileInfo, api) => {
+  const funcs = [
+    { name: 'beforeEach', index: 0 },
+    { name: 'afterEach', index: 0 },
+    { name: 'it', index: 1 },
+  ]
+
+  const j = api.jscodeshift
+
+  const removeReturn = (src, name, index) => {
+    return j(src)
+    .find(j.ExpressionStatement, {
+      expression: {
+        callee: {
+          type: 'Identifier',
+          name,
+        },
+      },
+    })
+    .replaceWith(({ node }) => {
+      let block = node.expression.arguments[index].body
+
+      if (block.body && block.body.length > 0) {
+        block.body = block.body.map((s) => {
+          if (s.type === 'ReturnStatement') {
+            const stat = j.expressionStatement(s.argument)
+
+            if (s.comments) {
+              stat.comments = s.comments
+            }
+
+            return stat
+          }
+
+          return s
+        })
+      }
+
+      return node
+    })
+    .toSource()
+  }
+
+  let src = fileInfo.source
+
+  funcs.forEach(({ name, index }) => {
+    src = removeReturn(src, name, index)
+  })
+
+  return src
+}

From a3b10696227472da9d9b0df3d5fec37cb7874317 Mon Sep 17 00:00:00 2001
From: KHeo <sainthkh@naver.com>
Date: Mon, 2 Dec 2019 18:19:46 +0900
Subject: [PATCH 17/18] Revert "Added test-no-return."

This reverts commit d610829e957e38a6d56c19ba2219681e3f6c65ec.
---
 bulk-decaffeinate.config.js                   |  1 -
 .../__testfixtures__/test-no-return.input.js  | 24 ---------
 .../__testfixtures__/test-no-return.output.js | 24 ---------
 scripts/decaff/__tests__/decaff.test.js       |  1 -
 scripts/decaff/test-no-return.js              | 51 -------------------
 5 files changed, 101 deletions(-)
 delete mode 100644 scripts/decaff/__testfixtures__/test-no-return.input.js
 delete mode 100644 scripts/decaff/__testfixtures__/test-no-return.output.js
 delete mode 100644 scripts/decaff/test-no-return.js

diff --git a/bulk-decaffeinate.config.js b/bulk-decaffeinate.config.js
index 8120ef9cf4b0..e7af5f254a2d 100644
--- a/bulk-decaffeinate.config.js
+++ b/bulk-decaffeinate.config.js
@@ -18,6 +18,5 @@ module.exports = {
     './scripts/decaff/empty-catch.js',
     './scripts/decaff/no-cond-assign.js',
     './scripts/decaff/arrow-comment.js',
-    './scripts/decaff/test-no-return.js',
   ],
 }
diff --git a/scripts/decaff/__testfixtures__/test-no-return.input.js b/scripts/decaff/__testfixtures__/test-no-return.input.js
deleted file mode 100644
index 07c28501686f..000000000000
--- a/scripts/decaff/__testfixtures__/test-no-return.input.js
+++ /dev/null
@@ -1,24 +0,0 @@
-context('a', function () {
-  beforeEach(() => {
-    doSomething()
-
-    return settings.write('something')
-  })
-
-  afterEach(() => {
-    return settings.reset()
-  })
-
-  it('test 1', function () {
-    cy.visit('hi/world')
-
-    return cy.click('abc')
-  })
-
-  it('test 2', () => {
-    return this.project.saveState()
-    .then((state) => {
-      expect(state).to.deep.eq({})
-    })
-  })
-})
diff --git a/scripts/decaff/__testfixtures__/test-no-return.output.js b/scripts/decaff/__testfixtures__/test-no-return.output.js
deleted file mode 100644
index e157967c67b0..000000000000
--- a/scripts/decaff/__testfixtures__/test-no-return.output.js
+++ /dev/null
@@ -1,24 +0,0 @@
-context('a', function () {
-  beforeEach(() => {
-    doSomething()
-
-    settings.write('something');
-  })
-
-  afterEach(() => {
-    settings.reset();
-  })
-
-  it('test 1', function () {
-    cy.visit('hi/world')
-
-    cy.click('abc');
-  })
-
-  it('test 2', () => {
-    this.project.saveState()
-    .then((state) => {
-      expect(state).to.deep.eq({})
-    });
-  })
-})
diff --git a/scripts/decaff/__tests__/decaff.test.js b/scripts/decaff/__tests__/decaff.test.js
index c613a1a0582b..4921d9b52b37 100644
--- a/scripts/decaff/__tests__/decaff.test.js
+++ b/scripts/decaff/__tests__/decaff.test.js
@@ -8,4 +8,3 @@ defineTest(__dirname, 'empty-catch')
 defineTest(__dirname, 'remove-comment-sharp')
 defineTest(__dirname, 'arrow-comment')
 defineTest(__dirname, 'no-cond-assign')
-defineTest(__dirname, 'test-no-return')
diff --git a/scripts/decaff/test-no-return.js b/scripts/decaff/test-no-return.js
deleted file mode 100644
index f3d39398ddbc..000000000000
--- a/scripts/decaff/test-no-return.js
+++ /dev/null
@@ -1,51 +0,0 @@
-module.exports = (fileInfo, api) => {
-  const funcs = [
-    { name: 'beforeEach', index: 0 },
-    { name: 'afterEach', index: 0 },
-    { name: 'it', index: 1 },
-  ]
-
-  const j = api.jscodeshift
-
-  const removeReturn = (src, name, index) => {
-    return j(src)
-    .find(j.ExpressionStatement, {
-      expression: {
-        callee: {
-          type: 'Identifier',
-          name,
-        },
-      },
-    })
-    .replaceWith(({ node }) => {
-      let block = node.expression.arguments[index].body
-
-      if (block.body && block.body.length > 0) {
-        block.body = block.body.map((s) => {
-          if (s.type === 'ReturnStatement') {
-            const stat = j.expressionStatement(s.argument)
-
-            if (s.comments) {
-              stat.comments = s.comments
-            }
-
-            return stat
-          }
-
-          return s
-        })
-      }
-
-      return node
-    })
-    .toSource()
-  }
-
-  let src = fileInfo.source
-
-  funcs.forEach(({ name, index }) => {
-    src = removeReturn(src, name, index)
-  })
-
-  return src
-}

From 0838b7f7f34e18d13837e40d8a1119adfdd7e6c1 Mon Sep 17 00:00:00 2001
From: Ben Kucera <14625260+Bkucera@users.noreply.github.com>
Date: Fri, 6 Dec 2019 12:18:28 -0500
Subject: [PATCH 18/18] fix arrow-comment

---
 scripts/decaff/arrow-comment.js | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/scripts/decaff/arrow-comment.js b/scripts/decaff/arrow-comment.js
index 044870f9b0e1..8607e1047cd7 100644
--- a/scripts/decaff/arrow-comment.js
+++ b/scripts/decaff/arrow-comment.js
@@ -15,9 +15,10 @@ module.exports = (fileInfo, api) => {
   })
   .replaceWith((nodePath) => {
     const { node } = nodePath
+    const comments = node.declarations[0].init.body.comments
 
-    if (node.declarations[0].init.body.comments.length > 0) {
-      node.comments = [...node.comments, ...node.declarations[0].init.body.comments]
+    if (comments && comments.length > 0) {
+      node.comments = [...node.comments, ...comments]
       node.declarations[0].init.body.comments = null
     }