Fix trailing semicolon corner case (#91)

* Add unit test

* Merge

* Allow 'trailingComma: false' as alternative to 'none'

* Implement fix

* 0.3.6

* Bump mo-fmt

* Update CI

* Create diff directory if not found

.github/workflows/tests.yml

@@ -26,6 +26,7 @@ jobs:
       with:
         node-version: ${{ matrix.node-version }}
         cache: 'npm'
+    - run: git clone https://github.com/dfinity/motoko.git ../motoko --depth 1
     - run: npm ci
     - run: npm i prettier
     - run: npm run build --if-present

package.json

@@ -1,6 +1,6 @@
 {
     "name": "prettier-plugin-motoko",
-    "version": "0.3.5",
+    "version": "0.3.6",
     "description": "A code formatter for the Motoko smart contract language.",
     "main": "lib/environments/node.js",
     "browser": "lib/environments/web.js",

packages/mo-fmt/package.json

@@ -1,6 +1,6 @@
 {
     "name": "mo-fmt",
-    "version": "0.3.5",
+    "version": "0.3.6",
     "description": "An easy-to-use Motoko formatter command.",
     "main": "src/cli.js",
     "bin": {
@@ -21,7 +21,7 @@
         "commander": "^9.4.0",
         "fast-glob": "^3.2.11",
         "prettier": "^2.7",
-        "prettier-plugin-motoko": "^0.3.5"
+        "prettier-plugin-motoko": "^0.3.6"
     },
     "devDependencies": {
         "@rollup/plugin-commonjs": "^22.0.2",

src/printers/motoko-tt-ast/print.ts

@@ -258,6 +258,7 @@ function printTokenTree(
         const results: Doc[] = [];
         let resultGroup: Doc[] = [];
         let ignoringNextStatement = false;
+        let allowTrailingSeparator = false;
         const endGroup = () => {
             if (resultGroup.length) {
                 results.push(fill(resultGroup));
@@ -292,15 +293,20 @@ function printTokenTree(
                 }
             }
 
+            // allow trailing delimiter for everything except comments
+            if (comment === undefined) {
+                // allow trailing comma/semicolon if something exists in the group other than a comment
+                allowTrailingSeparator = true;
+            }
             // check for prettier-ignore comments
-            if (comment) {
-                if (comment === 'prettier-ignore') {
-                    ignoringNextStatement = true;
-                }
+            else if (comment === 'prettier-ignore') {
+                ignoringNextStatement = true;
             }
 
             if (isSeparator) {
                 endGroup();
+                // reset to default
+                allowTrailingSeparator = false;
             }
 
             if (ignoringNextStatement) {
@@ -336,13 +342,17 @@ function printTokenTree(
 
                     // trailing delimiter
                     if (
+                        (allowTrailingSeparator ||
+                            !results.length ||
+                            isDelim) &&
                         (!isSeparator || isDelim) &&
                         !hasNestedGroup &&
                         !shouldKeepSameLine() &&
                         (groupType !== 'Paren' || results.length > 1) &&
                         (groupType === 'Unenclosed' || groupType === 'Curly'
                             ? options.semi
-                            : options.trailingComma !== 'none') &&
+                            : options.trailingComma &&
+                              options.trailingComma !== 'none') &&
                         !isPossiblyRecordExtension() &&
                         !(
                             groupType === 'Square' &&

tests/compiler.test.ts

@@ -0,0 +1,49 @@
+import prettier from 'prettier';
+import * as motokoPlugin from '../src/environments/node';
+import glob from 'fast-glob';
+import { join, basename } from 'path';
+import { readFileSync, writeFileSync, existsSync, mkdirSync } from 'fs';
+
+const prettierOptions: prettier.Options = {
+    plugins: [motokoPlugin],
+    filepath: 'Main.mo',
+};
+
+const format = (input: string, options?: prettier.Options): string => {
+    return prettier.format(input, { ...prettierOptions, ...options });
+};
+
+describe('Motoko compiler suite', () => {
+    test('generate diff files from compiler tests', () => {
+        for (const extension of ['mo', 'did']) {
+            let preOutput = '';
+            let postOutput = '';
+            for (const file of glob.sync(
+                join(__dirname, `../../motoko/test/**/*.${extension}`),
+            )) {
+                const code = readFileSync(file, 'utf-8');
+                const formatted = prettier.format(code, {
+                    filepath: file,
+                    plugins: [motokoPlugin],
+                    // semi: false,///
+                });
+                preOutput += `// >>> ${basename(file)} <<<\n\n${code}\n\n`;
+                postOutput += `// >>> ${basename(
+                    file,
+                )} <<<\n\n${formatted}\n\n`;
+            }
+            const generatedDir = join(__dirname, 'generated');
+            if (!existsSync(generatedDir)) {
+                mkdirSync(generatedDir);
+            }
+            writeFileSync(
+                join(generatedDir, `_CompilerTests_Before.${extension}_`),
+                preOutput,
+            );
+            writeFileSync(
+                join(generatedDir, `_CompilerTests_Formatted.${extension}_`),
+                postOutput,
+            );
+        }
+    });
+});

tests/formatter.test.ts

@@ -50,7 +50,8 @@ describe('Motoko formatter', () => {
         expect(format('let/*{{*/x = 0;//x\n (x)')).toStrictEqual(
             'let /*{{*/ x = 0; //x\n(x);\n',
         );
-        expect(format('\n/**/\n\n\n/**/')).toStrictEqual('/**/\n\n/**/;\n');
+        expect(format('/**//**/')).toStrictEqual('/**/ /**/\n');
+        expect(format('\n/**/\n\n\n/**/')).toStrictEqual('/**/\n\n/**/\n');
         expectFormatted('/*=*/\n');
         expectFormatted('/**=*/\n');
         expectFormatted('/**=**/\n');
@@ -352,32 +353,8 @@ describe('Motoko formatter', () => {
         expect(format('if(\nx) { y }')).toStrictEqual('if (\n  x\n) { y };\n');
     });
 
-    // test('generate diff files from compiler tests', () => {
-    //     for (const extension of ['mo', 'did']) {
-    //         let preOutput = '';
-    //         let postOutput = '';
-    //         for (const file of glob.sync(
-    //             join(__dirname, `../../motoko/test/**/*.${extension}`),
-    //         )) {
-    //             const code = readFileSync(file, 'utf-8');
-    //             const formatted = prettier.format(code, {
-    //                 filepath: file,
-    //                 plugins: [motokoPlugin],
-    //                 // semi: false,///
-    //             });
-    //             preOutput += `// >>> ${basename(file)} <<<\n\n${code}\n\n`;
-    //             postOutput += `// >>> ${basename(
-    //                 file,
-    //             )} <<<\n\n${formatted}\n\n`;
-    //         }
-    //         writeFileSync(
-    //             join(__dirname, `generated/_CompilerTests_Before.${extension}_`),
-    //             preOutput,
-    //         );
-    //         writeFileSync(
-    //             join(__dirname, `generated/_CompilerTests_Formatted.${extension}_`),
-    //             postOutput,
-    //         );
-    //     }
-    // });
+    test('trailing semicolon after block comment', () => {
+        expect(format("x;\n/**/")).toStrictEqual("x;\n/**/\n");
+        expect(format("x;\n/*\n*/")).toStrictEqual("x;\n/*\n*/\n");
+    });
 });