Fix OpenAPI YAML converts strings to boolean (#5456)

Problem: yaml 1.1 treats some string as other types of value. Check out:
https://perlpunk.github.io/yaml-test-schema/schemas.html
Fix: #5377
Solution: make serialization compatible with YAML 1.1
Todo: test other types (in next PR).

Author: wanlwanl

Diff for: .chronus/changes/wanl-fix-noway-yaml-2024-11-27-14-31-43.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/openapi3"
+---
+
+Fix: OpenAPI YAML converts strings to boolean

Diff for: packages/openapi3/src/openapi.ts

@@ -1844,6 +1844,7 @@ function serializeDocument(root: OpenAPI3Document, fileType: FileType): string {
         singleQuote: true,
         aliasDuplicateObjects: false,
         lineWidth: 0,
+        compat: "yaml-1.1",
       });
   }
 }

Diff for: packages/openapi3/test/emit-openapi.test.ts

@@ -0,0 +1,79 @@
+import { describe, expect, it } from "vitest";
+import { emitOpenApiWithDiagnostics } from "./test-host.js";
+
+describe("Scalar formats of serialized document in YAML", () => {
+  it("should add single quote for y|Y|yes|Yes|YES|n|N|no|No|NO|true|True|TRUE|false|False|FALSE|on|On|ON|off|Off|OFF", async () => {
+    const [_, __, content] = await emitOpenApiWithDiagnostics(`
+      enum TestEnum {
+        y: "y",
+        Y: "Y",
+        yes: "yes",
+        Yes: "Yes",
+        YES: "YES",
+        yEs: "yEs",
+        n: "n",
+        N: "N",
+        no: "no",
+        No: "No",
+        NO: "NO",
+        nO: "nO",
+        "true": "true",
+        True: "True",
+        TRUE: "TRUE",
+        tRUE: "tRUE",
+        "false": "false",
+        False: "False",
+        FALSE: "FALSE",
+        fALSE: "fALSE",
+        on: "on",
+        On: "On",
+        ON: "ON",
+        oN: "oN",
+        off: "off",
+        Off: "Off",
+        OFF: "OFF",
+        oFF: "oFF"
+      }
+      `);
+    expect(content).toBe(`openapi: 3.0.0
+info:
+  title: (title)
+  version: 0.0.0
+tags: []
+paths: {}
+components:
+  schemas:
+    TestEnum:
+      type: string
+      enum:
+        - 'y'
+        - 'Y'
+        - 'yes'
+        - 'Yes'
+        - 'YES'
+        - yEs
+        - 'n'
+        - 'N'
+        - 'no'
+        - 'No'
+        - 'NO'
+        - nO
+        - 'true'
+        - 'True'
+        - 'TRUE'
+        - tRUE
+        - 'false'
+        - 'False'
+        - 'FALSE'
+        - fALSE
+        - 'on'
+        - 'On'
+        - 'ON'
+        - oN
+        - 'off'
+        - 'Off'
+        - 'OFF'
+        - oFF
+`);
+  });
+});

Diff for: packages/openapi3/test/test-host.ts

@@ -11,6 +11,7 @@ import { RestTestLibrary } from "@typespec/rest/testing";
 import { VersioningTestLibrary } from "@typespec/versioning/testing";
 import { XmlTestLibrary } from "@typespec/xml/testing";
 import { ok } from "assert";
+import { parse } from "yaml";
 import { OpenAPI3EmitterOptions } from "../src/lib.js";
 import { OpenAPI3TestLibrary } from "../src/testing/index.js";
 import { OpenAPI3Document } from "../src/types.js";
@@ -56,9 +57,10 @@ export async function createOpenAPITestRunner({
 export async function emitOpenApiWithDiagnostics(
   code: string,
   options: OpenAPI3EmitterOptions = {},
-): Promise<[OpenAPI3Document, readonly Diagnostic[]]> {
+): Promise<[OpenAPI3Document, readonly Diagnostic[], string]> {
   const runner = await createOpenAPITestRunner();
-  const outputFile = resolveVirtualPath("openapi.json");
+  const fileType = options["file-type"] || "yaml";
+  const outputFile = resolveVirtualPath("openapi" + fileType === "json" ? ".json" : ".yaml");
   const diagnostics = await runner.diagnose(code, {
     noEmit: false,
     emit: ["@typespec/openapi3"],
@@ -68,8 +70,8 @@ export async function emitOpenApiWithDiagnostics(
   });
   const content = runner.fs.get(outputFile);
   ok(content, "Expected to have found openapi output");
-  const doc = JSON.parse(content);
-  return [doc, diagnostics];
+  const doc = fileType === "json" ? JSON.parse(content) : parse(content);
+  return [doc, diagnostics, content];
 }
 
 export async function diagnoseOpenApiFor(code: string, options: OpenAPI3EmitterOptions = {}) {