Merge pull request #49 from CodinGame/fix-unwanted-import

Fix unwanted import

rollup/rollup.config.ts

@@ -40,6 +40,7 @@ const PURE_FUNCTIONS = new Set([
 const EXTENSIONS = ['', '.ts', '.js']
 
 const SRC_DIR = path.resolve(__dirname, '../src')
+const DIST_DIR = path.resolve(__dirname, '../dist')
 const VSCODE_DIR = path.resolve(__dirname, '../vscode')
 const NODE_MODULES_DIR = path.resolve(__dirname, '../node_modules')
 const MONACO_EDITOR_DIR = path.resolve(NODE_MODULES_DIR, './monaco-editor')
@@ -88,13 +89,13 @@ const external: rollup.ExternalOption = (source) => {
   return externals.some(external => source === external || source.startsWith(`${external}/`))
 }
 
-export default (args: Record<string, string>): rollup.RollupOptions => {
+export default (args: Record<string, string>): rollup.RollupOptions[] => {
   const vscodeVersion = args['vscode-version']
   delete args['vscode-version']
   if (vscodeVersion == null) {
     throw new Error('Vscode version is mandatory')
   }
-  return rollup.defineConfig({
+  return rollup.defineConfig([{
     cache: false,
     treeshake: {
       annotations: true,
@@ -303,17 +304,85 @@ export default (args: Record<string, string>): rollup.RollupOptions => {
             right: ').then(module => module.default ?? module)'
           }
         }
-      }, {
-        name: 'cleanup',
-        renderChunk (code) {
-          return cleanup(code, null, {
-            comments: 'none',
-            sourcemap: false
-          }).code
-        }
       }
     ]
-  })
+  }, {
+    // 2nd pass to improve treeshaking
+    cache: false,
+    treeshake: {
+      annotations: true,
+      preset: 'smallest',
+      propertyReadSideEffects: false,
+      moduleSideEffects (id) {
+        return id.startsWith(DIST_DIR) || id.endsWith('.css')
+      }
+    },
+    external,
+    input: Object.values(input).map(f => `./dist/${path.basename(f, '.ts')}`),
+    output: [{
+      format: 'esm',
+      dir: 'dist',
+      entryFileNames: '[name].js',
+      chunkFileNames: '[name].js',
+      hoistTransitiveImports: false
+    }],
+    plugins: [{
+      name: 'improve-treeshaking',
+      transform (code) {
+        const ast = recast.parse(code, {
+          parser: require('recast/parsers/babylon')
+        })
+        let transformed: boolean = false
+        function addComment (node: recast.types.namedTypes.NewExpression | recast.types.namedTypes.CallExpression) {
+          if (!(node.comments ?? []).some(comment => comment.value === PURE_ANNO)) {
+            transformed = true
+            node.comments = [recast.types.builders.commentBlock(PURE_ANNO, true)]
+            return recast.types.builders.parenthesizedExpression(node)
+          }
+          return node
+        }
+        recast.visit(ast.program.body, {
+          visitCallExpression (path) {
+            const node = path.node
+            if (node.callee.type === 'MemberExpression') {
+              if (node.callee.property.type === 'Identifier') {
+                const name = getMemberExpressionPath(node.callee)
+                if ((name != null && PURE_FUNCTIONS.has(name)) || PURE_FUNCTIONS.has(node.callee.property.name)) {
+                  path.replace(addComment(node))
+                }
+              }
+            } else if (node.callee.type === 'Identifier' && PURE_FUNCTIONS.has(node.callee.name)) {
+              path.replace(addComment(node))
+            } else if (node.callee.type === 'FunctionExpression') {
+              // Mark IIFE as pure, because typescript compile enums as IIFE
+              path.replace(addComment(node))
+            }
+            this.traverse(path)
+            return undefined
+          },
+          visitThrowStatement () {
+            return false
+          }
+        })
+        // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+        if (transformed) {
+          code = recast.print(ast).code
+          code = code.replace(/\/\*#__PURE__\*\/\s+/g, '/*#__PURE__*/ ') // Remove space after PURE comment
+        }
+        return code
+      }
+    }, nodeResolve({
+      extensions: EXTENSIONS
+    }), {
+      name: 'cleanup',
+      renderChunk (code) {
+        return cleanup(code, null, {
+          comments: 'none',
+          sourcemap: false
+        }).code
+      }
+    }]
+  }])
 }
 
 function resolve (_path: string, fromPaths: string[]) {