prettierx space-before-function-paren option

README.md

@@ -14,7 +14,7 @@ prettierx <options> <file(s)>
 
 | Option | Default value | CLI Override | API Override | Description                    |
 | ------ | ------------- | ------------ | ------------ | ------------------------------ |
-| TBD    | TBD           | TBD          | TBD          | TBD                            |
+| Space before function parentheses | `false` | `--space-before-function-paren` | `spaceBeforeFunctionParen: <bool>` | Put a space before function parenthesis. |
 
 <!-- - FUTURE TBD prettierx vs prettier (???):
 ![Prettier Banner](https://raw.githubusercontent.com/prettier/prettier-logo/master/images/prettier-banner-light.png)

docs/options.md

@@ -170,6 +170,14 @@ These options cannot be used with `cursorOffset`.
 | `0`        | `--range-start <int>` | `rangeStart: <int>` |
 | `Infinity` | `--range-end <int>`   | `rangeEnd: <int>`   |
 
+## Space before function parentheses
+
+Put a space before function parenthesis.
+
+| Default | CLI Override                    | API Override                       |
+| ------- | ------------------------------- | ---------------------------------- |
+| `false` | `--space-before-function-paren` | `spaceBeforeFunctionParen: <bool>` |
+
 ## Parser
 
 Specify which parser to use.

src/language-js/options.js

@@ -40,6 +40,12 @@ module.exports = {
     oppositeDescription:
       "Do not print semicolons, except at the beginning of lines which may need them."
   },
+  spaceBeforeFunctionParen: {
+    category: CATEGORY_JAVASCRIPT,
+    type: "boolean",
+    default: false,
+    description: "Put a space before function parenthesis."
+  },
   singleQuote: commonOptions.singleQuote,
   jsxSingleQuote: {
     since: "1.15.0",

src/language-js/printer-estree.js

@@ -3736,14 +3736,16 @@ function printMethod(path, options, print) {
     key = concat(["[", key, "]"]);
   }
 
+  parts.push(key);
+
   parts.push(
-    key,
     concat(
       path.call(
         valuePath => [
           printFunctionTypeParameters(valuePath, options, print),
           group(
             concat([
+              options.spaceBeforeFunctionParen ? " " : "",
               printFunctionParams(valuePath, print, options),
               printReturnType(valuePath, print, options)
             ])
@@ -4234,6 +4236,7 @@ function printFunctionDeclaration(path, print, options) {
     printFunctionTypeParameters(path, options, print),
     group(
       concat([
+              options.spaceBeforeFunctionParen ? " " : "",
         printFunctionParams(path, print, options),
         printReturnType(path, print, options)
       ])

tests/space-before-function-paren/eslint-compat/__snapshots__/jsfmt.spec.js.snap

@@ -0,0 +1,150 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`eslint.js 1`] = `
+====================================options=====================================
+parsers: ["flow", "typescript"]
+printWidth: 80
+spaceBeforeFunctionParen: true
+                                                                                | printWidth
+=====================================input======================================
+/*eslint space-before-function-paren: "error"*/
+/*eslint-env es6*/
+
+function foo() {
+    // ...
+}
+
+var bar = function() {
+    // ...
+};
+
+var bar = function foo() {
+    // ...
+};
+
+class Foo {
+    constructor() {
+        // ...
+    }
+    bar() {
+        // ...
+    }
+}
+
+var foo = {
+    bar() {
+        // ...
+    }
+};
+
+var foo = async() => 1
+
+=====================================output=====================================
+/*eslint space-before-function-paren: "error"*/
+/*eslint-env es6*/
+
+function foo () {
+  // ...
+}
+
+var bar = function () {
+  // ...
+};
+
+var bar = function foo () {
+  // ...
+};
+
+class Foo {
+  constructor () {
+    // ...
+  }
+  bar () {
+    // ...
+  }
+}
+
+var foo = {
+  bar () {
+    // ...
+  }
+};
+
+var foo = async () => 1;
+
+================================================================================
+`;
+
+exports[`eslint.js 2`] = `
+====================================options=====================================
+parsers: ["flow", "typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+/*eslint space-before-function-paren: "error"*/
+/*eslint-env es6*/
+
+function foo() {
+    // ...
+}
+
+var bar = function() {
+    // ...
+};
+
+var bar = function foo() {
+    // ...
+};
+
+class Foo {
+    constructor() {
+        // ...
+    }
+    bar() {
+        // ...
+    }
+}
+
+var foo = {
+    bar() {
+        // ...
+    }
+};
+
+var foo = async() => 1
+
+=====================================output=====================================
+/*eslint space-before-function-paren: "error"*/
+/*eslint-env es6*/
+
+function foo() {
+  // ...
+}
+
+var bar = function() {
+  // ...
+};
+
+var bar = function foo() {
+  // ...
+};
+
+class Foo {
+  constructor() {
+    // ...
+  }
+  bar() {
+    // ...
+  }
+}
+
+var foo = {
+  bar() {
+    // ...
+  }
+};
+
+var foo = async () => 1;
+
+================================================================================
+`;

tests/space-before-function-paren/eslint-compat/eslint.js

@@ -0,0 +1,31 @@
+/*eslint space-before-function-paren: "error"*/
+/*eslint-env es6*/
+
+function foo() {
+    // ...
+}
+
+var bar = function() {
+    // ...
+};
+
+var bar = function foo() {
+    // ...
+};
+
+class Foo {
+    constructor() {
+        // ...
+    }
+    bar() {
+        // ...
+    }
+}
+
+var foo = {
+    bar() {
+        // ...
+    }
+};
+
+var foo = async() => 1

tests/space-before-function-paren/eslint-compat/jsfmt.spec.js

@@ -0,0 +1,2 @@
+run_spec(__dirname, ["flow", "typescript"], { spaceBeforeFunctionParen: true });
+run_spec(__dirname, ["flow", "typescript"]);