fix(vue): tweak semicolon for single expression in event bindings

src/common/internal-plugins.js

@@ -33,6 +33,10 @@ module.exports = [
         return eval("require")("../language-js/parser-babylon").parsers
           .__vue_expression;
       },
+      get __vue_event_binding() {
+        return eval("require")("../language-js/parser-babylon").parsers
+          .__vue_event_binding;
+      },
       // JS - Flow
       get flow() {
         return eval("require")("../language-js/parser-flow").parsers.flow;

src/language-html/printer-html.js

@@ -41,7 +41,11 @@ const {
 const preprocess = require("./preprocess");
 const assert = require("assert");
 const { insertPragma } = require("./pragma");
-const { printVueFor, printVueSlotScope } = require("./syntax-vue");
+const {
+  printVueFor,
+  printVueSlotScope,
+  isVueEventBindingExpression
+} = require("./syntax-vue");
 const { printImgSrcset } = require("./syntax-attribute");
 
 function concat(parts) {
@@ -942,17 +946,13 @@ function printEmbeddedAttributeValue(node, originalTextToDoc, options) {
     const jsExpressionBindingPatterns = ["^v-"];
 
     if (isKeyMatched(vueEventBindingPatterns)) {
-      // copied from https://github.com/vuejs/vue/blob/v2.5.17/src/compiler/codegen/events.js#L3-L4
-      const fnExpRE = /^([\w$_]+|\([^)]*?\))\s*=>|^function\s*\(/;
-      const simplePathRE = /^[A-Za-z_$][\w$]*(?:\.[A-Za-z_$][\w$]*|\['[^']*?']|\["[^"]*?"]|\[\d+]|\[[A-Za-z_$][\w$]*])*$/;
-
-      const value = getValue()
-        // https://github.com/vuejs/vue/blob/v2.5.17/src/compiler/helpers.js#L104
-        .trim();
+      const value = getValue();
       return printMaybeHug(
-        simplePathRE.test(value) || fnExpRE.test(value)
+        isVueEventBindingExpression(value)
           ? textToDoc(value, { parser: "__js_expression" })
-          : stripTrailingHardline(textToDoc(value, { parser: "babylon" }))
+          : stripTrailingHardline(
+              textToDoc(value, { parser: "__vue_event_binding" })
+            )
       );
     }
 

src/language-html/syntax-vue.js

@@ -66,7 +66,21 @@ function printVueSlotScope(value, textToDoc) {
   });
 }
 
+function isVueEventBindingExpression(eventBindingValue) {
+  // https://github.com/vuejs/vue/blob/v2.5.17/src/compiler/codegen/events.js#L3-L4
+  // arrow function or anonymous function
+  const fnExpRE = /^([\w$_]+|\([^)]*?\))\s*=>|^function\s*\(/;
+  // simple member expression chain (a, a.b, a['b'], a["b"], a[0], a[b])
+  const simplePathRE = /^[A-Za-z_$][\w$]*(?:\.[A-Za-z_$][\w$]*|\['[^']*?']|\["[^"]*?"]|\[\d+]|\[[A-Za-z_$][\w$]*])*$/;
+
+  // https://github.com/vuejs/vue/blob/v2.5.17/src/compiler/helpers.js#L104
+  const value = eventBindingValue.trim();
+
+  return fnExpRE.test(value) || simplePathRE.test(value);
+}
+
 module.exports = {
+  isVueEventBindingExpression,
   printVueFor,
   printVueSlotScope
 };

src/language-js/html-binding.js

@@ -45,6 +45,25 @@ function printHtmlBinding(path, options, print) {
   }
 }
 
+// based on https://github.com/prettier/prettier/blob/master/src/language-html/syntax-vue.js isVueEventBindingExpression()
+function isVueEventBindingExpression(node) {
+  switch (node.type) {
+    case "MemberExpression":
+      switch (node.property.type) {
+        case "Identifier":
+        case "NumericLiteral":
+        case "StringLiteral":
+          return isVueEventBindingExpression(node.object);
+      }
+      return false;
+    case "Identifier":
+      return true;
+    default:
+      return false;
+  }
+}
+
 module.exports = {
+  isVueEventBindingExpression,
   printHtmlBinding
 };

src/language-js/parser-babylon.js

@@ -41,44 +41,49 @@ function babylonOptions(extraOptions, extraPlugins) {
   );
 }
 
-function parse(text, parsers, opts) {
-  // Inline the require to avoid loading all the JS if we don't use it
-  const babylon = require("@babel/parser");
+function createParse(parseMethod) {
+  return (text, parsers, opts) => {
+    // Inline the require to avoid loading all the JS if we don't use it
+    const babylon = require("@babel/parser");
 
-  const combinations = [
-    babylonOptions({ strictMode: true }, ["decorators-legacy"]),
-    babylonOptions({ strictMode: false }, ["decorators-legacy"]),
-    babylonOptions({ strictMode: true }, [
-      ["decorators", { decoratorsBeforeExport: false }]
-    ]),
-    babylonOptions({ strictMode: false }, [
-      ["decorators", { decoratorsBeforeExport: false }]
-    ])
-  ];
+    const combinations = [
+      babylonOptions({ strictMode: true }, ["decorators-legacy"]),
+      babylonOptions({ strictMode: false }, ["decorators-legacy"]),
+      babylonOptions({ strictMode: true }, [
+        ["decorators", { decoratorsBeforeExport: false }]
+      ]),
+      babylonOptions({ strictMode: false }, [
+        ["decorators", { decoratorsBeforeExport: false }]
+      ])
+    ];
 
-  const parseMethod =
-    !opts || opts.parser === "babylon" ? "parse" : "parseExpression";
-
-  let ast;
-  try {
-    ast = tryCombinations(babylon[parseMethod].bind(null, text), combinations);
-  } catch (error) {
-    throw createError(
-      // babel error prints (l:c) with cols that are zero indexed
-      // so we need our custom error
-      error.message.replace(/ \(.*\)/, ""),
-      {
-        start: {
-          line: error.loc.line,
-          column: error.loc.column + 1
+    let ast;
+    try {
+      ast = tryCombinations(
+        babylon[parseMethod].bind(null, text),
+        combinations
+      );
+    } catch (error) {
+      throw createError(
+        // babel error prints (l:c) with cols that are zero indexed
+        // so we need our custom error
+        error.message.replace(/ \(.*\)/, ""),
+        {
+          start: {
+            line: error.loc.line,
+            column: error.loc.column + 1
+          }
         }
-      }
-    );
-  }
-  delete ast.tokens;
-  return postprocess(ast, Object.assign({}, opts, { originalText: text }));
+      );
+    }
+    delete ast.tokens;
+    return postprocess(ast, Object.assign({}, opts, { originalText: text }));
+  };
 }
 
+const parse = createParse("parse");
+const parseExpression = createParse("parseExpression");
+
 function tryCombinations(fn, combinations) {
   let error;
   for (let i = 0; i < combinations.length; i++) {
@@ -94,7 +99,7 @@ function tryCombinations(fn, combinations) {
 }
 
 function parseJson(text, parsers, opts) {
-  const ast = parse(text, parsers, Object.assign({}, opts, { parser: "json" }));
+  const ast = parseExpression(text, parsers, opts);
 
   ast.comments.forEach(assertJsonNode);
   assertJsonNode(ast);
@@ -164,17 +169,20 @@ const babylon = Object.assign(
   { parse, astFormat: "estree", hasPragma },
   locFns
 );
+const babylonExpression = Object.assign({}, babylon, {
+  parse: parseExpression
+});
 
 // Export as a plugin so we can reuse the same bundle for UMD loading
 module.exports = {
   parsers: {
     babylon,
-    json: Object.assign({}, babylon, {
+    json: Object.assign({}, babylonExpression, {
       hasPragma() {
         return true;
       }
     }),
-    json5: babylon,
+    json5: babylonExpression,
     "json-stringify": Object.assign(
       {
         parse: parseJson,
@@ -183,8 +191,10 @@ module.exports = {
       locFns
     ),
     /** @internal */
-    __js_expression: babylon,
+    __js_expression: babylonExpression,
     /** for vue filter */
-    __vue_expression: babylon
+    __vue_expression: babylonExpression,
+    /** for vue event binding to handle semicolon */
+    __vue_event_binding: babylon
   }
 };

src/language-js/printer-estree.js

@@ -34,7 +34,10 @@ const clean = require("./clean");
 const insertPragma = require("./pragma").insertPragma;
 const handleComments = require("./comments");
 const pathNeedsParens = require("./needs-parens");
-const { printHtmlBinding } = require("./html-binding");
+const {
+  printHtmlBinding,
+  isVueEventBindingExpression
+} = require("./html-binding");
 const preprocess = require("./preprocess");
 const {
   hasNode,
@@ -494,6 +497,21 @@ function printPathNoParens(path, options, print, args) {
       if (n.directive) {
         return concat([nodeStr(n.expression, options, true), semi]);
       }
+
+      if (options.parser === "__vue_event_binding") {
+        const parent = path.getParentNode();
+        if (
+          parent.type === "Program" &&
+          parent.body.length === 1 &&
+          parent.body[0] === n
+        ) {
+          return concat([
+            path.call(print, "expression"),
+            isVueEventBindingExpression(n.expression) ? ";" : ""
+          ]);
+        }
+      }
+
       // Do not append semicolon after the only JSX element in a program
       return concat([
         path.call(print, "expression"),