feat(jsii-reflect): track directory and package.json for Assembly (#4991)

It's occasionally useful to track the source for a loaded Assembly (specifically in `cdk-generate-synthetic-examples` we need this info to accurately track `"exports"`).

Attach it to the Assembly.

---

By submitting this pull request, I confirm that my contribution is made under the terms of the [Apache 2.0 license].

[Apache 2.0 license]: https://www.apache.org/licenses/LICENSE-2.0

Author: rix0rrr

packages/jsii-reflect/lib/assembly.ts

@@ -17,10 +17,30 @@ export class Assembly extends ModuleLike {
   public constructor(
     system: TypeSystem,
     public readonly spec: jsii.Assembly,
+    private readonly _directory?: string,
+    private readonly _packageJson?: any,
   ) {
     super(system);
   }
 
+  public get directory(): string {
+    if (!this._directory) {
+      throw new Error(
+        'A directory was not supplied when initializing this Assembly',
+      );
+    }
+    return this._directory;
+  }
+
+  public get packageJson(): any {
+    if (!this._packageJson) {
+      throw new Error(
+        'A package.json was not supplied when initializing this Assembly',
+      );
+    }
+    return this._packageJson;
+  }
+
   public get fqn(): string {
     return this.spec.name;
   }

packages/jsii-reflect/lib/type-system.ts

@@ -378,7 +378,19 @@ export class TypeSystem {
   ) {
     validateFeatureSubset(supportedFeatures);
     const contents = loadAssemblyFromFile(file, validate, supportedFeatures);
-    return new Assembly(this, contents);
+
+    const pjFile = path.join(path.dirname(file), 'package.json');
+    let pjData: any = {};
+    try {
+      pjData = JSON.parse(fs.readFileSync(pjFile, 'utf-8'));
+    } catch (e: any) {
+      // Opportunistically it's not a failure if the file doesn't exist
+      if (e.code !== 'ENOENT') {
+        throw new Error(`Error loading ${pjFile}: ${e}`);
+      }
+    }
+
+    return new Assembly(this, contents, path.dirname(file), pjData);
   }
 
   private addRoot(asm: Assembly) {

packages/jsii-reflect/test/type-system.test.ts

@@ -15,6 +15,14 @@ beforeAll(async () => {
   });
 });
 
+test('jsii-calc assembly has package.json data attached', () => {
+  const asm = typesys.assemblies.find((a) => a.name === 'jsii-calc');
+  expect(asm?.packageJson).toMatchObject({
+    name: 'jsii-calc',
+    homepage: 'https://github.com/aws/jsii',
+  });
+});
+
 test('TypeSystem.hasAssembly', () => {
   expect(typesys.includesAssembly('@foo/bar')).toBeFalsy();
   expect(typesys.includesAssembly('jsii-calc')).toBeTruthy();

packages/jsii-reflect/test/util.ts

@@ -15,6 +15,12 @@ export function assemblyFromSource(
   cb?: (obj: PackageInfo) => void,
 ): Assembly {
   const ass = sourceToAssemblyHelper(source, cb);
+
+  let pjData: any = {};
+  if (typeof source === 'object' && 'package.json' in source) {
+    pjData = JSON.parse(source['package.json']);
+  }
+
   const ts = new TypeSystem();
-  return ts.addAssembly(new Assembly(ts, ass));
+  return ts.addAssembly(new Assembly(ts, ass, '/fake-dir', pjData));
 }