Init template can define a project kind which decide if dependencies are added to peer or regular dependencies (#6923)

fix [#6602](#6602)

Author: timotheeguerin

.chronus/changes/init-project-target-2025-3-9-15-27-47.md

@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: feature
+packages:
+  - "@typespec/compiler"
+---
+
+Init templates can define a project kind which decide if dependencies are added to peer or regular dependencies

packages/compiler/.scripts/build-init-templates.ts

@@ -83,6 +83,7 @@ const builtInTemplates: Record<string, InitTemplate> = {
     files: [...(await localDir("rest"))],
   },
   "library-ts": {
+    target: "library",
     title: "TypeSpec library",
     description: "Build your own TypeSpec library with custom types, decorators or linters.",
     compilerVersion: minCompilerVersion,
@@ -94,6 +95,7 @@ const builtInTemplates: Record<string, InitTemplate> = {
     ],
   },
   "emitter-ts": {
+    target: "library",
     title: "TypeSpec emitter",
     description: "Create a new package that emits artifacts from TypeSpec.",
     compilerVersion: minCompilerVersion,

packages/compiler/src/init/init-template.ts

@@ -15,6 +15,13 @@ export interface InitTemplateInput {
 }
 
 export interface InitTemplate {
+  /**
+   * The kind of project this tempolate initialize. This will change things like where dependencies are added.
+   * For example, a library will add dependencies to `peer` and `dev` dependencies, while a project will add them to `dependencies`.
+   * @default "project"
+   */
+  target?: "library" | "project";
+
   /**
    * Name of the template
    */
@@ -114,6 +121,7 @@ export const InitTemplateSchema: JSONSchemaType<InitTemplate> = {
   properties: {
     title: { type: "string" },
     description: { type: "string" },
+    target: { type: "string", enum: ["library", "project"], default: "project", nullable: true },
     compilerVersion: { type: "string", nullable: true },
     libraries: {
       type: "array",

packages/compiler/src/init/scaffold.ts

@@ -109,33 +109,35 @@ async function writePackageJson(host: SystemHost, config: ScaffoldingConfig) {
   if (isFileSkipGeneration("package.json", config.template.files ?? [])) {
     return;
   }
-  const peerDependencies: Record<string, string> = {};
-  const devDependencies: Record<string, string> = {};
+
+  const dependencies: Record<string, string> = {};
 
   if (!config.template.skipCompilerPackage) {
-    peerDependencies["@typespec/compiler"] = "latest";
-    devDependencies["@typespec/compiler"] = "latest";
+    dependencies["@typespec/compiler"] = "latest";
   }
 
   for (const library of config.libraries) {
-    peerDependencies[library.name] = await getPackageVersion(library);
-    devDependencies[library.name] = await getPackageVersion(library);
+    dependencies[library.name] = await getPackageVersion(library);
   }
 
   for (const key of Object.keys(config.emitters)) {
-    peerDependencies[key] = await getPackageVersion(config.emitters[key]);
-    devDependencies[key] = await getPackageVersion(config.emitters[key]);
+    dependencies[key] = await getPackageVersion(config.emitters[key]);
   }
 
   const packageJson: PackageJson = {
     name: config.name,
     version: "0.1.0",
     type: "module",
-    peerDependencies,
-    devDependencies,
     private: true,
   };
 
+  if (config.template.target === "library") {
+    packageJson.peerDependencies = dependencies;
+    packageJson.devDependencies = dependencies;
+  } else {
+    packageJson.dependencies = dependencies;
+  }
+
   return host.writeFile(
     joinPaths(config.directory, "package.json"),
     JSON.stringify(packageJson, null, 2),

packages/compiler/templates/__snapshots__/rest/package.json

@@ -2,19 +2,12 @@
   "name": "rest",
   "version": "0.1.0",
   "type": "module",
-  "peerDependencies": {
+  "private": true,
+  "dependencies": {
     "@typespec/compiler": "latest",
     "@typespec/http": "latest",
     "@typespec/rest": "latest",
     "@typespec/openapi": "latest",
     "@typespec/openapi3": "latest"
-  },
-  "devDependencies": {
-    "@typespec/compiler": "latest",
-    "@typespec/http": "latest",
-    "@typespec/rest": "latest",
-    "@typespec/openapi": "latest",
-    "@typespec/openapi3": "latest"
-  },
-  "private": true
+  }
 }

packages/compiler/templates/scaffolding.json

@@ -67,6 +67,7 @@
     ]
   },
   "library-ts": {
+    "target": "library",
     "title": "TypeSpec library",
     "description": "Build your own TypeSpec library with custom types, decorators or linters.",
     "compilerVersion": "1.0.0",
@@ -143,6 +144,7 @@
     ]
   },
   "emitter-ts": {
+    "target": "library",
     "title": "TypeSpec emitter",
     "description": "Create a new package that emits artifacts from TypeSpec.",
     "compilerVersion": "1.0.0",

packages/compiler/test/init/init-template.test.ts

@@ -1,4 +1,4 @@
-import { deepStrictEqual, ok, strictEqual } from "assert";
+import { ok, strictEqual } from "assert";
 import { beforeEach, describe, expect, it } from "vitest";
 import { parse } from "yaml";
 import { InitTemplate } from "../../src/init/init-template.js";
@@ -38,18 +38,40 @@ async function runTemplate(
 }
 
 describe("libraries", () => {
+  it("adds libraries to peer and dev dependencies fields", async () => {
+    await runTemplate({
+      target: "library",
+      libraries: [{ name: "bar" }],
+    });
+
+    const pkgJson = JSON.parse(getOutputFile("package.json")!);
+
+    expect(pkgJson.peerDependencies).toEqual({
+      "@typespec/compiler": "latest",
+      bar: "latest",
+    });
+    expect(pkgJson.devDependencies).toEqual({
+      "@typespec/compiler": "latest",
+      bar: "latest",
+    });
+    expect(pkgJson.dependencies).toBeUndefined();
+  });
+
   it("templates can contain specific library versions to use", async () => {
     await runTemplate({
+      target: "library",
       libraries: [{ name: "foo", version: "~1.2.3" }, { name: "bar" }],
     });
 
-    deepStrictEqual(JSON.parse(getOutputFile("package.json")!).peerDependencies, {
+    const pkgJson = JSON.parse(getOutputFile("package.json")!);
+
+    expect(pkgJson.peerDependencies).toEqual({
       "@typespec/compiler": "latest",
       foo: "~1.2.3",
       bar: "latest",
     });
 
-    deepStrictEqual(JSON.parse(getOutputFile("package.json")!).devDependencies, {
+    expect(pkgJson.devDependencies).toEqual({
       "@typespec/compiler": "latest",
       foo: "~1.2.3",
       bar: "latest",
@@ -59,6 +81,23 @@ describe("libraries", () => {
   });
 });
 
+describe("project", () => {
+  it("adds libraries to dependencies field", async () => {
+    await runTemplate({
+      libraries: [{ name: "bar" }],
+    });
+
+    const pkgJson = JSON.parse(getOutputFile("package.json")!);
+
+    expect(pkgJson.dependencies).toEqual({
+      "@typespec/compiler": "latest",
+      bar: "latest",
+    });
+    expect(pkgJson.peerDependencies).toBeUndefined();
+    expect(pkgJson.devDependencies).toBeUndefined();
+  });
+});
+
 it("can generate .gitignore file by default", async () => {
   await runTemplate({});
   strictEqual(typeof getOutputFile(".gitignore"), "string");