feat: Support default exported functions (#99)

src/converter/convertFile.test.ts

@@ -91,5 +91,17 @@ describe('convertFile', () => {
 
       await expect(modifiedFile?.getFullText()).toMatchFileSnapshot(snapshot);
     });
+
+    it('handles functions exported as default from plain JavaScript files', async () => {
+      const projectDir = path.join(fixtures, 'module-exports-function-js');
+      const projectConfig = path.join(projectDir, 'tsconfig.json');
+      const snapshot = path.join(projectDir, 'src', 'build-example-index.snap.js');
+      const project = ProjectUtil.getProject(projectConfig);
+
+      const sourceFile = project.getSourceFile('build-example-index.js')!;
+      const modifiedFile = convertFile(sourceFile);
+
+      await expect(modifiedFile?.getFullText()).toMatchFileSnapshot(snapshot);
+    });
   });
 });

src/converter/replacer/replaceModuleExports.ts

@@ -1,30 +1,36 @@
 import {SourceFile, SyntaxKind} from 'ts-morph';
+import {NodeUtil} from '../../util/NodeUtil.js';
 
 export function replaceModuleExports(sourceFile: SourceFile) {
   let defaultExport: string | undefined = undefined;
   const namedExports: string[] = [];
 
-  // Iterate through all statements in the source file
   sourceFile.getStatements().forEach(statement => {
     try {
       if (statement.getKind() === SyntaxKind.ExpressionStatement) {
         const expressionStatement = statement.asKind(SyntaxKind.ExpressionStatement);
         if (!expressionStatement) {
           return;
         }
+
         const expression = expressionStatement.getExpression();
         if (expression.getKind() === SyntaxKind.BinaryExpression) {
           const binaryExpression = expression.asKind(SyntaxKind.BinaryExpression);
           if (!binaryExpression) {
             return;
           }
+
           const left = binaryExpression.getLeft().getText();
-          const right = binaryExpression.getRight().getText();
+          const right = binaryExpression.getRight();
 
-          if (left === 'module.exports') {
-            defaultExport = right;
+          // Handle `module.exports = <expression>;`
+          if (left === 'module.exports' && right) {
+            const {comment} = NodeUtil.extractComment(binaryExpression.getLeft());
+            defaultExport = right.getText();
+            sourceFile.addStatements(`${comment}export default ${defaultExport};`);
             statement.remove();
-          } else if (left.startsWith('module.exports.')) {
+          } else if (left.startsWith('module.exports.') && right) {
+            // Handle `module.exports.<name> = <value>;`
             const exportName = left.split('.')[2];
             if (exportName) {
               namedExports.push(exportName);
@@ -35,27 +41,19 @@ export function replaceModuleExports(sourceFile: SourceFile) {
       }
     } catch (error: unknown) {
       console.error(` There was an issue with "${sourceFile.getFilePath()}":`, error);
-      process.exit(1);
     }
   });
 
   try {
-    if (defaultExport) {
-      sourceFile.addExportAssignment({
-        expression: defaultExport,
-        isExportEquals: false,
-      });
-    }
-
-    namedExports.forEach(name => {
+    if (namedExports.length > 0) {
       sourceFile.addExportDeclaration({
-        namedExports: [name],
+        namedExports,
       });
-    });
+    }
   } catch (error: unknown) {
     console.error(` There was an issue with "${sourceFile.getFilePath()}":`, error);
   }
 
-  const madeChanges = namedExports.length || defaultExport;
-  return !!madeChanges;
+  const madeChanges = defaultExport !== undefined || namedExports.length > 0;
+  return madeChanges;
 }

src/converter/replacer/replaceRequire.ts

@@ -1,4 +1,5 @@
 import {SourceFile, SyntaxKind, VariableStatement} from 'ts-morph';
+import {NodeUtil} from '../../util/NodeUtil.js';
 
 /**
  * Replaces a CommonJS require statement with an ESM import declaration.
@@ -61,10 +62,8 @@ export function replaceRequires(sourceFile: SourceFile) {
   if (hasShebang) {
     // The full text contains both comments and the following statment,
     // so we are separating the statement into comments and the instruction that follow on the next line.
-    const statementWithComment = firstStatement.getFullText();
-    const pureStatement = firstStatement.getText();
-    shebangText = statementWithComment.replace(pureStatement, '');
-    const lineAfterShebang = statementWithComment.replace(shebangText, '');
+    const {statement: lineAfterShebang, comment} = NodeUtil.extractComment(firstStatement);
+    shebangText = comment;
     // We remove the node containing the shebang comment (and the following statement) to insert only the pure statement.
     const index = firstStatement.getChildIndex();
     firstStatement.remove();

src/test/fixtures/module-exports-function-js/src/build-example-index-markdown.js

@@ -0,0 +1,4 @@
+import path from 'path';
+import info from './example-info.json';
+
+export default function buildExampleMarkdown(names, exampleBasePaths) {}

src/test/fixtures/module-exports-function-js/src/build-example-index-markdown.snap.js

@@ -0,0 +1,4 @@
+const path = require('path');
+const info = require('./example-info.json');
+
+module.exports = function buildExampleMarkdown(names, exampleBasePaths) {};

src/test/fixtures/module-exports-function-js/src/build-example-index.js

@@ -0,0 +1,4 @@
+const path = require('path');
+
+/** This comment should be kept. */
+module.exports = function buildExampleIndex(names, exampleBasePaths) {};

src/test/fixtures/module-exports-function-js/src/build-example-index.snap.js

@@ -0,0 +1,4 @@
+import path from "path";
+
+/** This comment should be kept. */
+export default function buildExampleIndex(names, exampleBasePaths) {};

src/test/fixtures/module-exports-function-js/tsconfig.json

@@ -0,0 +1,11 @@
+{
+  "compilerOptions": {
+    "allowJs": true,
+    "esModuleInterop": true,
+    "forceConsistentCasingInFileNames": true,
+    "module": "Node16",
+    "skipLibCheck": true,
+    "strict": true,
+    "target": "ES2020"
+  }
+}

src/test/fixtures/module-exports/src/main.snap.ts

@@ -1,6 +1,5 @@
 const Benny = 1;
 const Code = 2;
-
 export default Benny;
 
 export { Code };

src/util/NodeUtil.ts

@@ -0,0 +1,14 @@
+import {Expression, Statement} from 'ts-morph';
+
+export class NodeUtil {
+  static extractComment(input: Statement | Expression) {
+    const statementWithComment = input.getFullText();
+    const pureStatement = input.getText();
+    const comment = statementWithComment.replace(pureStatement, '');
+    const statement = statementWithComment.replace(comment, '');
+    return {
+      comment,
+      statement,
+    };
+  }
+}