Fix emit of bundled schemas when has references and is used multiple times

common/changes/@typespec/json-schema/js-fix-duplicate-def_2023-07-04-21-12.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@typespec/json-schema",
+      "comment": "Fix a bug that could result in a schema being bundled more than once.",
+      "type": "none"
+    }
+  ],
+  "packageName": "@typespec/json-schema"
+}

packages/json-schema/src/json-schema-emitter.ts

@@ -569,7 +569,7 @@ export class JsonSchemaEmitter extends TypeEmitter<Record<string, any>, JSONSche
         throw new Error("Emit error - multiple decls in single schema per file mode");
       }
 
-      content = decls[0].value;
+      content = { ...decls[0].value };
 
       if (sourceFile.meta.bundledRefs.length > 0) {
         // bundle any refs, including refs of refs

packages/json-schema/test/bundling.test.ts

@@ -48,4 +48,50 @@ describe("bundling", () => {
     assert.strictEqual(schemas["test.json"].$defs, undefined);
     assert.strictEqual(schemas["Bar.json"].$id, "Bar.json");
   });
+
+  it("doesn't create duplicate defs for transitive references", async () => {
+    const schemas = await emitSchema(
+      `
+      model A {}
+
+      model B {
+        refA: A;
+      }
+
+      @jsonSchema
+      model C {
+        refB: B;
+      }
+
+      @jsonSchema
+      model D {
+        refB: B;
+      }
+    `,
+      {},
+      { emitNamespace: false, emitTypes: ["C", "D"] }
+    );
+
+    const depSchemas = {
+      B: {
+        $schema: "https://json-schema.org/draft/2020-12/schema",
+        $id: "B.json",
+        type: "object",
+        properties: {
+          refA: {
+            $ref: "A.json",
+          },
+        },
+        required: ["refA"],
+      },
+      A: {
+        $schema: "https://json-schema.org/draft/2020-12/schema",
+        $id: "A.json",
+        type: "object",
+        properties: {},
+      },
+    };
+    assert.deepStrictEqual(schemas["C.json"].$defs, depSchemas);
+    assert.deepStrictEqual(schemas["D.json"].$defs, depSchemas);
+  });
 });

packages/json-schema/test/utils.ts

@@ -23,7 +23,7 @@ export async function getHostForCadlFile(contents: string, decorators?: Record<s
 export async function emitSchema(
   code: string,
   options: JSONSchemaEmitterOptions = {},
-  testOptions: { emitNamespace: boolean } = { emitNamespace: true }
+  testOptions: { emitNamespace?: boolean; emitTypes?: string[] } = { emitNamespace: true }
 ) {
   if (!options["file-type"]) {
     options["file-type"] = "json";
@@ -37,7 +37,14 @@ export async function emitSchema(
     emitterOutputDir: "cadl-output",
     options,
   } as any);
-  emitter.emitType(host.program.resolveTypeReference("test")[0]!);
+  if (testOptions.emitTypes === undefined) {
+    emitter.emitType(host.program.resolveTypeReference("test")[0]!);
+  } else {
+    for (const name of testOptions.emitTypes) {
+      emitter.emitType(host.program.resolveTypeReference(name)[0]!);
+    }
+  }
+
   await emitter.writeOutput();
   const schemas: Record<string, any> = {};
   const files = await emitter.getProgram().host.readDir("./cadl-output");