fix(rosetta): python identifiers mishandle identifier translations wi…

…th capital letters (#4644)

Fixes aws/aws-cdk#29138

Our python translation currently translates `sizeInMBs` to `size_in_mbs` for the python examples. However, the actual property is named `size_in_m_bs`. This is because we are currently handling identifiers with the regex `[^A-Z][A-Z]`, which misses the `MB` pair. 

I cannot see a use case where we would want to handle _identifiers_ this way (as opposed to interface names ala `IInterface`), so I've changed the logic.



---

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/languages/python.ts

@@ -111,7 +111,7 @@ export class PythonVisitor extends DefaultVisitor<PythonLanguageContext> {
    * Bump this when you change something in the implementation to invalidate
    * existing cached translations.
    */
-  public static readonly VERSION = '2';
+  public static readonly VERSION = '3';
 
   public readonly language = TargetLanguage.PYTHON;
   public readonly defaultContext = {};
@@ -818,7 +818,7 @@ function mangleIdentifier(originalIdentifier: string) {
     return originalIdentifier;
   }
   // Turn into snake-case
-  const cased = originalIdentifier.replace(/[^A-Z][A-Z]/g, (m) => `${m[0].slice(0, 1)}_${m.slice(1).toLowerCase()}`);
+  const cased = originalIdentifier.replace(/[A-Z]/g, (m) => `_${m.toLowerCase()}`);
   return IDENTIFIER_KEYWORDS.includes(cased) ? `${cased}_` : cased;
 }
 

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

@@ -218,3 +218,33 @@ test('declarations are translated correctly in all jsii languages', () => {
     assembly.cleanup();
   }
 });
+
+test('handling capital letters in identifiers', () => {
+  // Create an assembly in a temp directory
+  const assembly = TestJsiiModule.fromSource(
+    {
+      'index.ts': `
+      export interface InterfaceA {
+        readonly sizeInMBs: Number;
+      }
+      `,
+    },
+    {
+      name: 'my_assembly',
+      jsii: DUMMY_JSII_CONFIG,
+    },
+  );
+  try {
+    const ts = assembly.translateHere(
+      ["import * as masm from 'my_assembly';", 'declare let intA: masm.InterfaceA;', 'intA = { sizeInMBs: 3 };'].join('\n'),
+    );
+
+    expect(ts.get(TargetLanguage.PYTHON)?.source).toEqual(
+      ['import example_test_demo as masm', '# int_a: masm.InterfaceA', 'int_a = masm.InterfaceA(size_in_m_bs=3)'].join('\n'),
+    );
+    expect(ts.get(TargetLanguage.JAVA)?.source).toEqual(['import example.test.demo.*;', 'InterfaceA intA;', 'intA = InterfaceA.builder().sizeInMBs(3).build();'].join('\n'));
+    expect(ts.get(TargetLanguage.CSHARP)?.source).toEqual(['using Example.Test.Demo;', 'InterfaceA intA;', 'intA = new InterfaceA { SizeInMBs = 3 };'].join('\n'));
+  } finally {
+    assembly.cleanup();
+  }
+});