Fixes package linking when a filename casing changes

__tests__/commands/install/integration.js

@@ -48,6 +48,19 @@ async function mockConstants(base: Config, mocks: Object, cb: (config: Config) =
 beforeEach(request.__resetAuthedRequests);
 afterEach(request.__resetAuthedRequests);
 
+test.concurrent('installing a package with a renamed file should not delete it', async () => {
+  await runInstall({}, 'case-sensitivity', async (config, reporter): Promise<void> => {
+    const pkgJson = await fs.readJson(`${config.cwd}/package.json`);
+    pkgJson.dependencies['pkg'] = 'file:./pkg-b';
+    await fs.writeFile(`${config.cwd}/package.json`, JSON.stringify(pkgJson));
+
+    const reInstall = new Install({}, config, reporter, await Lockfile.fromDirectory(config.cwd));
+    await reInstall.init();
+
+    expect(await fs.exists(`${config.cwd}/node_modules/pkg/state.js`)).toEqual(true);
+  });
+});
+
 test.concurrent('properly find and save build artifacts', async () => {
   await runInstall({}, 'artifacts-finds-and-saves', async (config): Promise<void> => {
     const integrity = await fs.readJson(path.join(config.cwd, 'node_modules', constants.INTEGRITY_FILENAME));

__tests__/fixtures/install/case-sensitivity/package.json

@@ -0,0 +1,5 @@
+{
+    "dependencies": {
+        "pkg": "file:./pkg-a"
+    }
+}

__tests__/fixtures/install/case-sensitivity/pkg-a/State.js

@@ -0,0 +1 @@
+Hello World

__tests__/fixtures/install/case-sensitivity/pkg-a/package.json

@@ -0,0 +1,4 @@
+{
+    "name": "pkg",
+    "version": "1.0.0"
+}

__tests__/fixtures/install/case-sensitivity/pkg-b/package.json

@@ -0,0 +1,4 @@
+{
+    "name": "pkg",
+    "version": "2.0.0"
+}

__tests__/fixtures/install/case-sensitivity/pkg-b/state.js

@@ -0,0 +1 @@
+Hello World

src/util/fs.js

@@ -151,7 +151,7 @@ async function buildActionsForCopy(
   }
 
   for (const loc of possibleExtraneous) {
-    if (files.has(loc)) {
+    if (files.has(loc.toLowerCase())) {
       possibleExtraneous.delete(loc);
     }
   }
@@ -163,12 +163,14 @@ async function buildActionsForCopy(
     const {src, dest, type} = data;
     const onFresh = data.onFresh || noop;
     const onDone = data.onDone || noop;
-    if (files.has(dest)) {
-      // TODO https://github.com/yarnpkg/yarn/issues/3751
-      // related to bundled dependencies handling
-      reporter.warn(`The same file ${dest} can't be copied twice in one bulk copy`);
+
+    // TODO https://github.com/yarnpkg/yarn/issues/3751
+    // related to bundled dependencies handling
+    if (files.has(dest.toLowerCase())) {
+      reporter.warn(`The case-insensitive file ${dest} shouldn't be copied twice in one bulk copy`);
+    } else {
+      files.add(dest.toLowerCase());
     }
-    files.add(dest);
 
     if (type === 'symlink') {
       await mkdirp(path.dirname(dest));
@@ -279,7 +281,7 @@ async function buildActionsForCopy(
 
       const destParts = dest.split(path.sep);
       while (destParts.length) {
-        files.add(destParts.join(path.sep));
+        files.add(destParts.join(path.sep).toLowerCase());
         destParts.pop();
       }
 
@@ -358,7 +360,7 @@ async function buildActionsForHardlink(
   }
 
   for (const loc of possibleExtraneous) {
-    if (files.has(loc)) {
+    if (files.has(loc.toLowerCase())) {
       possibleExtraneous.delete(loc);
     }
   }
@@ -370,7 +372,7 @@ async function buildActionsForHardlink(
     const {src, dest} = data;
     const onFresh = data.onFresh || noop;
     const onDone = data.onDone || noop;
-    if (files.has(dest)) {
+    if (files.has(dest.toLowerCase())) {
       // Fixes issue https://github.com/yarnpkg/yarn/issues/2734
       // When bulk hardlinking we have A -> B structure that we want to hardlink to A1 -> B1,
       // package-linker passes that modules A1 and B1 need to be hardlinked,
@@ -379,7 +381,7 @@ async function buildActionsForHardlink(
       onDone();
       return;
     }
-    files.add(dest);
+    files.add(dest.toLowerCase());
 
     if (events.ignoreBasenames.indexOf(path.basename(src)) >= 0) {
       // ignored file
@@ -463,7 +465,7 @@ async function buildActionsForHardlink(
 
       const destParts = dest.split(path.sep);
       while (destParts.length) {
-        files.add(destParts.join(path.sep));
+        files.add(destParts.join(path.sep).toLowerCase());
         destParts.pop();
       }
 
@@ -541,7 +543,11 @@ export async function copyBulk(
       const cleanup = () => delete currentlyWriting[data.dest];
       reporter.verbose(reporter.lang('verboseFileCopy', data.src, data.dest));
       return (currentlyWriting[data.dest] = readFileBuffer(data.src)
-        .then(d => {
+        .then(async d => {
+          // we need to do this because of case-insensitive filesystems, which wouldn't properly
+          // change the file name in case of a file being renamed
+          await unlink(data.dest);
+
           return writeFile(data.dest, d, {mode: data.mode});
         })
         .then(() => {