Fix trailing comma in multi-line array type (#88)

* Fix trailing comma in multi-line array type

* 0.3.5

* Comment out diff test

* Update mo-fmt

package.json

@@ -1,6 +1,6 @@
 {
     "name": "prettier-plugin-motoko",
-    "version": "0.3.4",
+    "version": "0.3.5",
     "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": "0.3.4",
+    "version": "0.3.5",
     "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": "^0.3.4"
+        "prettier-plugin-motoko": "^0.3.5"
     },
     "devDependencies": {
         "@rollup/plugin-commonjs": "^22.0.2",

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

@@ -322,7 +322,7 @@ function printTokenTree(
                 // add everything except trailing delimiter
                 if (!isDelim || i !== trees.length - 1) {
                     resultArray.push(
-                        isDelim 
+                        isDelim
                             ? printToken(getGroupDelimToken(groupType))
                             : printTokenTree(a, path, options, print, args),
                     );
@@ -342,7 +342,12 @@ function printTokenTree(
                         (groupType === 'Unenclosed' || groupType === 'Curly'
                             ? options.semi
                             : options.trailingComma !== 'none') &&
-                        !isPossiblyRecordExtension()
+                        !isPossiblyRecordExtension() &&
+                        !(
+                            groupType === 'Square' &&
+                            results.length === 1 &&
+                            !isSeparator
+                        ) // possibly array type
                     ) {
                         results.push(
                             ifBreak(printToken(getGroupDelimToken(groupType))),

tests/formatter.test.ts

@@ -274,7 +274,7 @@ describe('Motoko formatter', () => {
             `${'x'.repeat(80)}[0];\n`,
         );
         expect(format(`${'x'.repeat(80)}[\n0]`)).toStrictEqual(
-            `${'x'.repeat(80)}[\n  0,\n];\n`,
+            `${'x'.repeat(80)}[\n  0\n];\n`,
         );
         expect(format(`${'x'.repeat(80)}[0,]`)).toStrictEqual(
             `${'x'.repeat(80)}[0];\n`,
@@ -342,6 +342,12 @@ describe('Motoko formatter', () => {
         expect(format("'\\\"'; //abc")).toStrictEqual("'\\\"'; //abc\n");
     });
 
+    test('trailing comma in square brackets', () => {
+        expect(format("[\na,b]")).toStrictEqual("[\n  a,\n  b,\n];\n");
+        expect(format("[\na,]")).toStrictEqual("[\n  a,\n];\n");
+        expect(format("x : [\nT\n]")).toStrictEqual("x : [\n  T\n];\n");
+    });
+
     // test('generate diff files from compiler tests', () => {
     //     for (const extension of ['mo', 'did']) {
     //         let preOutput = '';