New: template-curly-spacing rule (fixes #5049)

conf/eslint.json

@@ -194,6 +194,7 @@
         "space-unary-ops": 0,
         "spaced-comment": 0,
         "strict": 0,
+        "template-curly-spacing": 0,
         "use-isnan": 2,
         "valid-jsdoc": 0,
         "valid-typeof": 2,

docs/rules/README.md

@@ -236,6 +236,7 @@ These rules are only relevant to ES6 environments.
 * [prefer-spread](prefer-spread.md) - suggest using the spread operator instead of `.apply()`.
 * [prefer-template](prefer-template.md) - suggest using template literals instead of strings concatenation
 * [require-yield](require-yield.md) - disallow generator functions that do not have `yield`
+* [template-curly-spacing](template-curly-spacing.md) - enforce spacing around embedded expressions of template strings (fixable)
 * [yield-star-spacing](yield-star-spacing.md) - enforce spacing around the `*` in `yield*` expressions (fixable)
 
 

docs/rules/template-curly-spacing.md

@@ -0,0 +1,79 @@
+# Enforce Usage of Spacing in Template Strings (template-curly-spacing)
+
+We can embed expressions in template strings with using a pair of `${` and `}`.
+This rule can force usage of spacing inside of the curly brace pair according to style guides.
+
+```js
+let hello = `hello, ${people.name}!`;
+```
+
+**Fixable:** This rule is automatically fixable using the `--fix` flag on the command line.
+
+## Rule Details
+
+This rule aims to maintain consistency around the spacing inside of template literals.
+
+### Options
+
+```json
+{
+    "template-curly-spacing": [2, "never"]
+}
+```
+
+This rule has one option which has either `"never"` or `"always"` as value.
+
+* `"never"` (by default) - Disallows spaces inside of the curly brace pair.
+* `"always"` - Requires one or more spaces inside of the curly brace pair.
+
+The following patterns are considered problems when configured `"never"`:
+
+```js
+/*eslint template-curly-spacing: 2*/
+
+`hello, ${ people.name}!`;  /*error Unexpected space(s) after '${'.*/
+`hello, ${people.name }!`;  /*error Unexpected space(s) before '}'.*/
+
+`hello, ${ people.name }!`; /*error Unexpected space(s) after '${'.*/
+                            /*error Unexpected space(s) before '}'.*/
+```
+
+The following patterns are considered problems when configured `"always"`:
+
+```js
+/*eslint template-curly-spacing: [2, "always"]*/
+
+`hello, ${ people.name}!`;  /*error Expected space(s) before '}'.*/
+`hello, ${people.name }!`;  /*error Expected space(s) after '${'.*/
+
+`hello, ${people.name}!`;   /*error Expected space(s) after '${'.*/
+                            /*error Expected space(s) before '}'.*/
+```
+
+The following patterns are not considered problems when configured `"never"`:
+
+```js
+/*eslint template-curly-spacing: 2*/
+
+`hello, ${people.name}!`;
+
+`hello, ${
+    people.name
+}!`;
+```
+
+The following patterns are not considered problems when configured `"always"`:
+
+```js
+/*eslint template-curly-spacing: [2, "always"]*/
+
+`hello, ${ people.name }!`;
+
+`hello, ${
+    people.name
+}!`;
+```
+
+## When Not To Use It
+
+If you don't want to be notified about usage of spacing inside of template strings, then it's safe to disable this rule.

lib/rules/template-curly-spacing.js

@@ -0,0 +1,102 @@
+/**
+ * @fileoverview Rule to enforce spacing around embedded expressions of template strings
+ * @author Toru Nagashima
+ * @copyright 2016 Toru Nagashima. All rights reserved.
+ * See LICENSE file in root directory for full license.
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+var astUtils = require("../ast-utils");
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+var OPEN_PAREN = /\$\{$/;
+var CLOSE_PAREN = /^\}/;
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = function(context) {
+    var sourceCode = context.getSourceCode();
+    var always = context.options[0] === "always";
+    var prefix = always ? "Expected" : "Unexpected";
+
+    /**
+     * Checks spacing before `}` of a given token.
+     * @param {Token} token - A token to check. This is a Template token.
+     * @returns {void}
+     */
+    function checkSpacingBefore(token) {
+        var prevToken = sourceCode.getTokenBefore(token);
+        if (prevToken &&
+            CLOSE_PAREN.test(token.value) &&
+            astUtils.isTokenOnSameLine(prevToken, token) &&
+            sourceCode.isSpaceBetweenTokens(prevToken, token) !== always
+        ) {
+            context.report({
+                loc: token.loc.start,
+                message: prefix + " space(s) before '}'.",
+                fix: function(fixer) {
+                    if (always) {
+                        return fixer.insertTextBefore(token, " ");
+                    }
+                    return fixer.removeRange([
+                        prevToken.range[1],
+                        token.range[0]
+                    ]);
+                }
+            });
+        }
+    }
+
+    /**
+     * Checks spacing after `${` of a given token.
+     * @param {Token} token - A token to check. This is a Template token.
+     * @returns {void}
+     */
+    function checkSpacingAfter(token) {
+        var nextToken = sourceCode.getTokenAfter(token);
+        if (nextToken &&
+            OPEN_PAREN.test(token.value) &&
+            astUtils.isTokenOnSameLine(token, nextToken) &&
+            sourceCode.isSpaceBetweenTokens(token, nextToken) !== always
+        ) {
+            context.report({
+                loc: {
+                    line: token.loc.end.line,
+                    column: token.loc.end.column - 2
+                },
+                message: prefix + " space(s) after '${'.",
+                fix: function(fixer) {
+                    if (always) {
+                        return fixer.insertTextAfter(token, " ");
+                    }
+                    return fixer.removeRange([
+                        token.range[1],
+                        nextToken.range[0]
+                    ]);
+                }
+            });
+        }
+    }
+
+    return {
+        TemplateElement: function(node) {
+            var token = sourceCode.getFirstToken(node);
+            checkSpacingBefore(token);
+            checkSpacingAfter(token);
+        }
+    };
+};
+
+module.exports.schema = [
+    {enum: ["always", "never"]}
+];

tests/lib/rules/template-curly-spacing.js

@@ -0,0 +1,104 @@
+/**
+ * @fileoverview Tests for template-curly-spacing rule.
+ * @author Toru Nagashima
+ * @copyright 2016 Toru Nagashima. All rights reserved.
+ * See LICENSE file in root directory for full license.
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+var rule = require("../../../lib/rules/template-curly-spacing"),
+    RuleTester = require("../../../lib/testers/rule-tester");
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+var ruleTester = new RuleTester();
+ruleTester.run("template-curly-spacing", rule, {
+    valid: [
+        {code: "{ foo }"},
+        {code: "`${foo} ${bar}`", parserOptions: {ecmaVersion: 6}},
+        {code: "`${foo} ${bar} ${\n  baz\n}`", options: ["never"], parserOptions: {ecmaVersion: 6}},
+        {code: "`${ foo } ${ bar } ${\n  baz\n}`", options: ["always"], parserOptions: {ecmaVersion: 6}},
+        {code: "tag`${foo} ${bar}`", parserOptions: {ecmaVersion: 6}},
+        {code: "tag`${foo} ${bar} ${\n  baz\n}`", options: ["never"], parserOptions: {ecmaVersion: 6}},
+        {code: "tag`${ foo } ${ bar } ${\n  baz\n}`", options: ["always"], parserOptions: {ecmaVersion: 6}}
+    ],
+    invalid: [
+        {
+            code: "`${ foo } ${ bar }`",
+            output: "`${foo} ${bar}`",
+            errors: [
+                {message: "Unexpected space(s) after '${'.", column: 2},
+                {message: "Unexpected space(s) before '}'.", column: 9},
+                {message: "Unexpected space(s) after '${'.", column: 11},
+                {message: "Unexpected space(s) before '}'.", column: 18}
+            ],
+            parserOptions: {ecmaVersion: 6}
+        },
+        {
+            code: "`${ foo } ${ bar }`",
+            output: "`${foo} ${bar}`",
+            errors: [
+                {message: "Unexpected space(s) after '${'.", column: 2},
+                {message: "Unexpected space(s) before '}'.", column: 9},
+                {message: "Unexpected space(s) after '${'.", column: 11},
+                {message: "Unexpected space(s) before '}'.", column: 18}
+            ],
+            options: ["never"],
+            parserOptions: {ecmaVersion: 6}
+        },
+        {
+            code: "`${foo} ${bar}`",
+            output: "`${ foo } ${ bar }`",
+            errors: [
+                {message: "Expected space(s) after '${'.", column: 2},
+                {message: "Expected space(s) before '}'.", column: 7},
+                {message: "Expected space(s) after '${'.", column: 9},
+                {message: "Expected space(s) before '}'.", column: 14}
+            ],
+            options: ["always"],
+            parserOptions: {ecmaVersion: 6}
+        },
+        {
+            code: "tag`${ foo } ${ bar }`",
+            output: "tag`${foo} ${bar}`",
+            errors: [
+                {message: "Unexpected space(s) after '${'.", column: 5},
+                {message: "Unexpected space(s) before '}'.", column: 12},
+                {message: "Unexpected space(s) after '${'.", column: 14},
+                {message: "Unexpected space(s) before '}'.", column: 21}
+            ],
+            parserOptions: {ecmaVersion: 6}
+        },
+        {
+            code: "tag`${ foo } ${ bar }`",
+            output: "tag`${foo} ${bar}`",
+            errors: [
+                {message: "Unexpected space(s) after '${'.", column: 5},
+                {message: "Unexpected space(s) before '}'.", column: 12},
+                {message: "Unexpected space(s) after '${'.", column: 14},
+                {message: "Unexpected space(s) before '}'.", column: 21}
+            ],
+            options: ["never"],
+            parserOptions: {ecmaVersion: 6}
+        },
+        {
+            code: "tag`${foo} ${bar}`",
+            output: "tag`${ foo } ${ bar }`",
+            errors: [
+                {message: "Expected space(s) after '${'.", column: 5},
+                {message: "Expected space(s) before '}'.", column: 10},
+                {message: "Expected space(s) after '${'.", column: 12},
+                {message: "Expected space(s) before '}'.", column: 17}
+            ],
+            options: ["always"],
+            parserOptions: {ecmaVersion: 6}
+        }
+    ]
+});