fix(jsii): require statement for the warning file is generated when i…

…t's not used (#3184)

When `add-deprecation-warnings` is `true` but no calls were injected in a given file, the `require` statement for `.warnings.jsii.js` should not be generated.


---

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/lib/transforms/deprecation-warnings.ts

@@ -333,6 +333,8 @@ module.exports.DeprecationError = DeprecationError;
 }
 
 class Transformer {
+  private warningCallsWereInjected = false;
+
   public constructor(
     private readonly typeChecker: ts.TypeChecker,
     private readonly context: ts.TransformationContext,
@@ -342,9 +344,11 @@ class Transformer {
   ) {}
 
   public transform<T extends ts.Node>(node: T): T {
+    this.warningCallsWereInjected = false;
+
     const result = this.visitEachChild(node);
 
-    if (ts.isSourceFile(result)) {
+    if (ts.isSourceFile(result) && this.warningCallsWereInjected) {
       const importDir = path.relative(
         path.dirname(result.fileName),
         this.projectRoot,
@@ -368,6 +372,8 @@ class Transformer {
   private visitor<T extends ts.Node>(node: T): ts.VisitResult<T> {
     if (ts.isMethodDeclaration(node) && node.body != null) {
       const statements = this.getStatementsForDeclaration(node);
+      this.warningCallsWereInjected =
+        this.warningCallsWereInjected || statements.length > 0;
       return ts.updateMethod(
         node,
         node.decorators,
@@ -385,6 +391,8 @@ class Transformer {
       ) as any;
     } else if (ts.isGetAccessorDeclaration(node) && node.body != null) {
       const statements = this.getStatementsForDeclaration(node);
+      this.warningCallsWereInjected =
+        this.warningCallsWereInjected || statements.length > 0;
       return ts.updateGetAccessor(
         node,
         node.decorators,
@@ -399,6 +407,8 @@ class Transformer {
       ) as any;
     } else if (ts.isSetAccessorDeclaration(node) && node.body != null) {
       const statements = this.getStatementsForDeclaration(node);
+      this.warningCallsWereInjected =
+        this.warningCallsWereInjected || statements.length > 0;
       return ts.updateSetAccessor(
         node,
         node.decorators,
@@ -412,6 +422,8 @@ class Transformer {
       ) as any;
     } else if (ts.isConstructorDeclaration(node) && node.body != null) {
       const statements = this.getStatementsForDeclaration(node);
+      this.warningCallsWereInjected =
+        this.warningCallsWereInjected || statements.length > 0;
       return ts.updateConstructor(
         node,
         node.decorators,

packages/jsii/test/deprecation-warnings.test.ts

@@ -388,6 +388,26 @@ describe('Call injections', () => {
     );
   });
 
+  test('does not generate a require statement when no calls were injected', async () => {
+    const result = await compileJsiiForTest(
+      {
+        'index.ts': `export * from './some/folder/handler'`,
+        'some/folder/handler.ts': `
+          export function handler(event: any) { return event; }
+        `,
+      },
+      undefined /* callback */,
+      { addDeprecationWarnings: true },
+    );
+
+    const expectedPath = ['..', '..', '.warnings.jsii.js'].join('/');
+
+    const content = jsFile(result, 'some/folder/handler');
+    expect(content).not.toContain(
+      `const jsiiDeprecationWarnings = require("${expectedPath}")`,
+    );
+  });
+
   test('deprecated methods', async () => {
     const result = await compileJsiiForTest(
       `