build: share API declarations across module formats (#1793)

## Summary

- emit the API package declaration files once under `out/types`
- point both ESM and CommonJS package exports to the shared declaration
entry point
- keep separate ESM and CommonJS JavaScript builds
- ensure package validation rejects duplicated declarations under the
runtime output directories

## Validation

- `npm run compile`
- `npm run test:package`

---------

Copilot-Session: cb57f94f-69e9-4501-a84e-7661b191ceba

Author: edvilme

api/package.json

@@ -12,14 +12,14 @@
         "Environments"
     ],
     "main": "./out/cjs/main.cjs",
-    "types": "./out/cjs/main.d.ts",
+    "types": "./out/types/main.d.ts",
     "exports": {
         "import": {
-            "types": "./out/esm/main.d.ts",
+            "types": "./out/types/main.d.ts",
             "default": "./out/esm/main.mjs"
         },
         "require": {
-            "types": "./out/cjs/main.d.ts",
+            "types": "./out/types/main.d.ts",
             "default": "./out/cjs/main.cjs"
         }
     },
@@ -41,7 +41,8 @@
         "prepack": "npm run all:publish",
         "all:publish": "git clean -xfd . && npm install && npm run copy:sources && npm run compile",
         "copy:sources": "node ./scripts/copy-sources.cjs",
-        "compile": "npm run compile:esm && npm run compile:cjs",
+        "compile": "npm run clean && npm run compile:types && npm run compile:esm && npm run compile:cjs",
+        "compile:types": "tsc -b ./tsconfig.types.json",
         "compile:esm": "tsc -b ./tsconfig.esm.json && mve out/esm/main.js out/esm/main.mjs && node -e \"require('fs').writeFileSync('out/esm/package.json', '{\\\"type\\\":\\\"module\\\"}')\"",
         "compile:cjs": "tsc -b ./tsconfig.cjs.json && mve out/cjs/main.js out/cjs/main.cjs",
         "clean": "node -e \"const fs = require('fs'); fs.rmSync('./out', { recursive: true, force: true });\"",

api/scripts/test-package.cjs

@@ -97,14 +97,14 @@ try {
     );
     const installedPackageJson = JSON.parse(fs.readFileSync(path.join(installedPackageRoot, 'package.json'), 'utf8'));
     assert.strictEqual(installedPackageJson.main, './out/cjs/main.cjs');
-    assert.strictEqual(installedPackageJson.types, './out/cjs/main.d.ts');
+    assert.strictEqual(installedPackageJson.types, './out/types/main.d.ts');
     assert.deepStrictEqual(installedPackageJson.exports, {
         import: {
-            types: './out/esm/main.d.ts',
+            types: './out/types/main.d.ts',
             default: './out/esm/main.mjs',
         },
         require: {
-            types: './out/cjs/main.d.ts',
+            types: './out/types/main.d.ts',
             default: './out/cjs/main.cjs',
         },
     });
@@ -119,6 +119,17 @@ try {
     ]) {
         assert.ok(fs.statSync(path.resolve(installedPackageRoot, target)).isFile(), `${target} must be a file`);
     }
+    for (const runtimeOutput of ['esm', 'cjs']) {
+        const runtimeOutputRoot = path.join(installedPackageRoot, 'out', runtimeOutput);
+        const duplicateDeclarations = fs
+            .readdirSync(runtimeOutputRoot, { recursive: true })
+            .filter((entry) => entry.endsWith('.d.ts'));
+        assert.deepStrictEqual(
+            duplicateDeclarations,
+            [],
+            `${runtimeOutputRoot} must not contain declaration files: ${duplicateDeclarations.join(', ')}`,
+        );
+    }
 
     const requireFromConsumer = createRequire(path.join(testRoot, 'legacy', 'consumer.cjs'));
     const commonJsModule = requireFromConsumer('@vscode/python-environments');

api/tsconfig.base.json

@@ -2,7 +2,7 @@
     "compilerOptions": {
         "target": "ES2020",
         "lib": ["ES2020"],
-        "declaration": true,
+        "declaration": false,
         "strict": true,
         "rootDir": "src",
         "esModuleInterop": true,

api/tsconfig.types.json

@@ -0,0 +1,10 @@
+{
+    "extends": "./tsconfig.base.json",
+    "compilerOptions": {
+        "declaration": true,
+        "emitDeclarationOnly": true,
+        "module": "esnext",
+        "moduleResolution": "bundler",
+        "outDir": "./out/types"
+    }
+}