feat: allow namespaced component names

OpenAPI generated by Typespec will use namespace-qualified component names in
the generated OpenAPI, when types are in a different namespace from that of the
OpenAPI spec. Additionally, components derived from model properties such as
parameters or headers use the property name as a suffix.

This updates the componentNameCase rule to allow PascalCase component names
with an optional dot.case namespace prefix and optional snake_case suffix.

DGP-50

src/rulesets/rest/2022-05-25/__tests__/__snapshots__/specification-rules.test.ts.snap

@@ -379,7 +379,7 @@ exports[`specification rules fails when components are not PascalCase 1`] = `
     },
     "condition": undefined,
     "docsLink": "https://github.com/snyk/sweater-comb/blob/main/docs/standards/rest.md#referenced-entities",
-    "error": "Expected thingResourceResponse to be pascal case",
+    "error": "Expected thingResourceResponse to be pascal case in component thingResourceResponse",
     "exempted": false,
     "expected": undefined,
     "isMust": true,
@@ -466,6 +466,114 @@ exports[`specification rules fails when components are not PascalCase 1`] = `
 ]
 `;
 
+exports[`specification rules passes when components are namespaced PascalCase 1`] = `
+[
+  {
+    "change": {
+      "location": {
+        "conceptualLocation": {},
+        "conceptualPath": [],
+        "jsonPath": "",
+        "kind": "specification",
+      },
+      "value": {
+        "info": {
+          "title": "Empty",
+          "version": "0.0.0",
+        },
+        "openapi": "3.1.0",
+        "x-snyk-api-stability": "wip",
+      },
+    },
+    "condition": undefined,
+    "docsLink": "https://github.com/snyk/sweater-comb/blob/main/docs/standards/rest.md#referenced-entities",
+    "error": undefined,
+    "exempted": false,
+    "expected": undefined,
+    "isMust": true,
+    "isShould": false,
+    "name": "component names",
+    "passed": true,
+    "received": undefined,
+    "severity": 2,
+    "type": "requirement",
+    "where": "specification",
+  },
+  {
+    "change": {
+      "location": {
+        "conceptualLocation": {},
+        "conceptualPath": [],
+        "jsonPath": "",
+        "kind": "specification",
+      },
+      "value": {
+        "info": {
+          "title": "Empty",
+          "version": "0.0.0",
+        },
+        "openapi": "3.1.0",
+        "x-snyk-api-stability": "wip",
+      },
+    },
+    "condition": undefined,
+    "docsLink": "https://github.com/snyk/sweater-comb/blob/main/docs/standards/rest.md#tags",
+    "error": undefined,
+    "exempted": false,
+    "expected": undefined,
+    "isMust": true,
+    "isShould": false,
+    "name": "open api version names",
+    "passed": true,
+    "received": undefined,
+    "severity": 2,
+    "type": "requirement",
+    "where": "specification",
+  },
+  {
+    "change": {
+      "changeType": "changed",
+      "changed": {
+        "after": {
+          "info": {
+            "title": "Empty",
+            "version": "0.0.0",
+          },
+          "openapi": "3.1.0",
+          "x-snyk-api-stability": "wip",
+        },
+        "before": {
+          "info": {
+            "title": "Empty",
+            "version": "0.0.0",
+          },
+          "openapi": "3.1.0",
+        },
+      },
+      "location": {
+        "conceptualLocation": {},
+        "conceptualPath": [],
+        "jsonPath": "",
+        "kind": "specification",
+      },
+    },
+    "condition": undefined,
+    "docsLink": "https://github.com/snyk/sweater-comb/blob/main/docs/standards/rest.md#polymorphic-objects",
+    "error": undefined,
+    "exempted": false,
+    "expected": undefined,
+    "isMust": true,
+    "isShould": false,
+    "name": "no mapping objects in discriminators",
+    "passed": true,
+    "received": undefined,
+    "severity": 2,
+    "type": "changed",
+    "where": "specification",
+  },
+]
+`;
+
 exports[`specification rules uncompiled specs passes when /openapi endpoint isn't specified 1`] = `
 [
   {

src/rulesets/rest/2022-05-25/__tests__/specification-rules.test.ts

@@ -30,6 +30,11 @@ describe("specification rules", () => {
             description: "Response containing a single thing resource object",
             properties: {},
           },
+          "IO.SNYK.SOMETHING.ThingResourceResponse": {
+            type: "object",
+            description: "Response containing a single thing resource object",
+            properties: {},
+          },
         },
       },
     } as OpenAPIV3.Document;
@@ -45,6 +50,45 @@ describe("specification rules", () => {
     expect(results).toMatchSnapshot();
   });
 
+  test("passes when components are namespaced PascalCase", async () => {
+    const afterJson = {
+      ...baseJson,
+      [stabilityKey]: "wip",
+      paths: {},
+      components: {
+        schemas: {
+          "something.ThingResourceResponse": {
+            type: "object",
+            description: "Response containing a single thing resource object",
+            properties: {},
+          },
+          "io.snyk.something.ThingResourceResponse": {
+            type: "object",
+            description: "Response containing a single thing resource object",
+            properties: {},
+          },
+        },
+        parameters: {
+          "io.snyk.something.SomeApiRequest.some_param": {
+            description: "Response containing a single thing resource object",
+            in: "path",
+            name: "some_param"
+          },
+        },
+      },
+    } as OpenAPIV3.Document;
+    const ruleRunner = new RuleRunner([specificationRules]);
+    const ruleInputs = {
+      ...TestHelpers.createRuleInputs(baseJson, afterJson),
+      context,
+    };
+    const results = await ruleRunner.runRulesWithFacts(ruleInputs);
+
+    expect(results.length).toBeGreaterThan(0);
+    expect(results.every((result) => result.passed)).toBe(true);
+    expect(results).toMatchSnapshot();
+  });
+
   test("fails if a discriminator is added with a mapping object", async () => {
     const afterJson = {
       ...baseJson,

src/rulesets/rest/2022-05-25/specification-rules.ts

@@ -1,8 +1,45 @@
 import { RuleError, Ruleset, SpecificationRule } from "@useoptic/rulesets-base";
-import { pascalCase } from "change-case";
+import { dotCase, pascalCase, snakeCase } from "change-case";
 import { links } from "../../../docs";
 import { stabilityKey } from "./constants";
 
+interface componentName {
+  localName: string;
+  localProp?: string;
+  ns?: string;
+}
+
+/**
+ * Decode the component name from a possibly namespace and property-qualified OpenAPI component name.
+ *
+ * @param name An OpenAPI component name
+ * @returns Tuple containing the local name (without namespace) and its namespace prefix (undefined if not namespaced).
+ */
+const decodeComponentName = (name: string): componentName => {
+  const parts = name.split(".");
+  if (parts.length > 1) {
+    const lastPart = parts[parts.length - 1];
+    if (lastPart === snakeCase(lastPart)) {
+      // Component is derived from a Typespec model property, of the form namespace.ModelName.property_name.
+      // This is the case for shared parameter or header components, for example.
+      return {
+        localName: parts[parts.length - 2],
+        localProp: lastPart,
+        ns: parts.slice(0, parts.length - 2).join("."),
+      }
+    } else {
+      // Component is derived from a Typespec model, of the form namespace.ModelName.property_name.
+      // This is the case for schema components.
+      return {
+        localName: parts[parts.length - 1],
+        ns: parts.slice(0, parts.length - 1).join("."),
+      };
+    }
+  } else {
+    return { localName: name };
+  }
+};
+
 const componentNameCase = new SpecificationRule({
   name: "component names",
   docsLink: links.standards.referencedEntities,
@@ -22,9 +59,21 @@ const componentNameCase = new SpecificationRule({
             specification.raw.components?.[componentType] || {},
           );
           for (const componentName of componentNames) {
-            if (pascalCase(componentName) !== componentName) {
+            const {localName, localProp, ns} = decodeComponentName(componentName);
+            if (pascalCase(localName) !== localName) {
+              throw new RuleError({
+                message: `Expected ${localName} to be pascal case in component ${componentName}`,
+              });
+            }
+            if (localProp && snakeCase(localProp) !== localProp) {
+              throw new RuleError({
+                message: `Expected ${localProp} to be snake case in component ${componentName}`,
+              });
+
+            }
+            if (ns && dotCase(ns) !== ns) {
               throw new RuleError({
-                message: `Expected ${componentName} to be pascal case`,
+                message: `Expected ${ns} to be dot case in component ${componentName}`,
               });
             }
           }