Typespec Generation for Empty Schema #4923

.chronus/changes/fix-open-api-empty-schema-2024-10-1-6-50-22.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/openapi3"
+---
+
+tsp-openapi3 - fixes typespec generation for empty schema

packages/openapi3/src/cli/actions/convert/generators/generate-model.ts

@@ -66,7 +66,11 @@ function generateScalar(scalar: TypeSpecScalar, context: Context): string {
   definitions.push(...generateDecorators(scalar.decorators));
   const type = context.generateTypeFromRefableSchema(scalar.schema, scalar.scope);
 
-  definitions.push(`scalar ${scalar.name} extends ${type};`);
+  if (type === "unknown") {
+    definitions.push(`scalar ${scalar.name};`);
+  } else {
+    definitions.push(`scalar ${scalar.name} extends ${type};`);
+  }
 
   return definitions.join("\n");
 }

packages/openapi3/test/tsp-openapi3/convert-openapi3-doc.test.ts

@@ -45,3 +45,44 @@ it("should convert an OpenAPI3 document to a formatted TypeSpec program", async
     ),
   );
 });
+
+it("converts an OpenAPI 3 document with an empty schema to a valid TypeSpec representation", async () => {
+  const tsp = await convertOpenAPI3Document({
+    info: {
+      title: "Test",
+      version: "0.0.0",
+    },
+    openapi: "3.0.0",
+    paths: {},
+    components: {
+      schemas: {
+        Foo: {},
+      },
+    },
+  });
+
+  strictEqual(
+    tsp,
+    await formatTypeSpec(
+      `
+      import "@typespec/http";
+      import "@typespec/openapi";
+      import "@typespec/openapi3";
+
+      using Http;
+      using OpenAPI;
+
+      @service({
+        title: "Test",
+      })
+      @info({
+        version: "0.0.0",
+      })
+      namespace Test;
+
+      scalar Foo;
+        `,
+      { printWidth: 100, tabWidth: 2 },
+    ),
+  );
+});