fix(rosetta): didCompile evaluates to true when compilation not att…

…empted (#3149)

When `rosetta:extract` is run, the property `didCompile` evalutes to `true`
even when compilation was not attempted. This causes lots of confusion.
The correct way to handle this is to return `undefined` when compilation is
not attempted. Then, (I assume) `didCompile` will not show up in the tablet
file at all when compilation is not asked for (via `--compile` or `strict`.

---

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

packages/jsii-rosetta/lib/translate.ts

@@ -152,6 +152,7 @@ export class SnippetTranslator {
   public readonly compileDiagnostics: ts.Diagnostic[] = [];
   private readonly visibleSpans: Spans;
   private readonly compilation!: CompilationResult;
+  private readonly tryCompile: boolean;
 
   public constructor(snippet: TypeScriptSnippet, private readonly options: SnippetTranslatorOptions = {}) {
     const compiler = options.compiler ?? new TypeScriptCompiler();
@@ -170,7 +171,9 @@ export class SnippetTranslator {
     this.visibleSpans = Spans.visibleSpansFromSource(source);
 
     // This makes it about 5x slower, so only do it on demand
-    if (options.includeCompilerDiagnostics || snippet.strict) {
+    // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
+    this.tryCompile = (options.includeCompilerDiagnostics || snippet.strict) ?? false;
+    if (this.tryCompile) {
       const program = this.compilation.program;
       const diagnostics = [
         ...neverThrowing(program.getGlobalDiagnostics)(),
@@ -208,8 +211,11 @@ export class SnippetTranslator {
     }
   }
 
+  /**
+   * Returns a boolean if compilation was attempted, and undefined if it was not.
+   */
   public get didSuccessfullyCompile() {
-    return this.compileDiagnostics.length === 0;
+    return this.tryCompile ? this.compileDiagnostics.length === 0 : undefined;
   }
 
   public renderUsing(visitor: AstHandler<any>) {

packages/jsii-rosetta/test/translate.test.ts

@@ -112,3 +112,35 @@ test('Snippets from different locations have different keys', () => {
 
   expect(snippetKey(snippet1)).not.toEqual(snippetKey(snippet2));
 });
+
+test('didSuccessfullyCompile is true when compilation is attempted', () => {
+  const visibleSource = 'console.log("banana");';
+
+  const snippet: TypeScriptSnippet = {
+    visibleSource,
+    location: { api: { api: 'type', fqn: 'my.class' } },
+  };
+
+  // WHEN
+  const subject = new SnippetTranslator(snippet, {
+    includeCompilerDiagnostics: true,
+  });
+  subject.renderUsing(new PythonVisitor());
+
+  expect(subject.didSuccessfullyCompile).toBeTruthy();
+});
+
+test('didSuccessfullyCompile is undefined when compilation is not attempted', () => {
+  const visibleSource = 'console.log("banana");';
+
+  const snippet: TypeScriptSnippet = {
+    visibleSource,
+    location: { api: { api: 'type', fqn: 'my.class' } },
+  };
+
+  // WHEN
+  const subject = new SnippetTranslator(snippet);
+  subject.renderUsing(new PythonVisitor());
+
+  expect(subject.didSuccessfullyCompile).toBeUndefined();
+});