New: max-lines rule (fixes #6078)

conf/eslint.json

@@ -167,6 +167,7 @@
         "lines-around-comment": "off",
         "max-depth": "off",
         "max-len": "off",
+        "max-lines": "off",
         "max-nested-callbacks": "off",
         "max-params": "off",
         "max-statements": "off",

docs/rules/README.md

@@ -174,6 +174,7 @@ These rules relate to style guidelines, and are therefore quite subjective:
 * [lines-around-comment](lines-around-comment.md): require empty lines around comments
 * [max-depth](max-depth.md): enforce a maximum depth that blocks can be nested
 * [max-len](max-len.md): enforce a maximum line length
+* [max-lines](max-lines.md): enforce a maximum file length
 * [max-nested-callbacks](max-nested-callbacks.md): enforce a maximum depth that callbacks can be nested
 * [max-params](max-params.md): enforce a maximum number of parameters in `function` definitions
 * [max-statements](max-statements.md): enforce a maximum number of statements allowed in `function` blocks

docs/rules/max-lines.md

@@ -0,0 +1,125 @@
+# enforce a maximum file length (max-lines)
+
+Some people consider large files a code smell. Large files tend to do a lot of things and can make it hard following what's going. While there is not an objective maximum number of lines considered acceptable in a file, most people would agree it should not be in the thousands. Recommendations usually range from 100 to 500 lines.
+
+## Rule Details
+
+This rule enforces a maximum number of lines per file, in order to aid in maintainability and reduce complexity.
+
+
+## Options
+
+This rule has a number or object option:
+
+* `"max"` (default `300`) enforces a maximum number of lines in a file
+
+* `"skipBlankLines": true` ignore lines made up purely of whitespace.
+
+* `"skipComment": true` ignore lines containing just comments
+
+### code
+
+Examples of **incorrect** code for this rule with a max value of `2`:
+
+```js
+/*eslint max-lines: ["error", 2]*/
+var a,
+    b,
+    c;
+```
+
+```js
+/*eslint max-lines: ["error", 2]*/
+
+var a,
+    b,c;
+```
+
+```js
+/*eslint max-lines: ["error", 2]*/
+// a comment
+var a,
+    b,c;
+```
+
+Examples of **correct** code for this rule with a max value of `2`:
+
+```js
+/*eslint max-lines: ["error", 2]*/
+var a,
+    b, c;
+```
+
+```js
+/*eslint max-lines: ["error", 2]*/
+
+var a, b, c;
+```
+
+```js
+/*eslint max-lines: ["error", 2]*/
+// a comment
+var a, b, c;
+```
+
+### skipBlankLines
+
+Examples of **incorrect** code for this rule with the `{ "skipBlankLines": true }` option:
+
+```js
+/*eslint max-lines: ["error", 2, {"skipBlankLines": true}]*/
+
+var a,
+    b,
+    c;
+```
+
+Examples of **correct** code for this rule with the `{ "skipBlankLines": true }` option:
+
+```js
+/*eslint max-lines: ["error", 2, {"skipBlankLines": true}]*/
+
+var a,
+    b, c;
+```
+
+### skipComments
+
+Examples of **incorrect** code for this rule with the `{ "skipComments": true }` option:
+
+```js
+/*eslint max-lines: ["error", 2, {"skipComments": true}]*/
+// a comment
+var a,
+    b,
+    c;
+```
+
+Examples of **correct** code for this rule with the `{ "skipComments": true }` option:
+
+```js
+/*eslint max-lines: ["error", 2, {"skipComments": true}]*/
+// a comment
+var a,
+    b, c;
+```
+
+## When Not To Use It
+
+You can turn this rule off if you are not concerned with the number of lines in your files.
+
+## Further reading
+
+* [Software Module size and file size](http://www.mind2b.com/component/content/article/24-software-module-size-and-file-size)
+
+## Related Rules
+
+* [complexity](complexity.md)
+* [max-depth](max-depth.md)
+* [max-nested-callbacks](max-nested-callbacks.md)
+* [max-params](max-params.md)
+* [max-statements](max-statements.md)
+
+## Compatibility
+
+* **JSCS**: [maximumNumberOfLines](http://jscs.info/rule/maximumNumberOfLines)

lib/rules/max-lines.js

@@ -0,0 +1,148 @@
+/**
+ * @fileoverview enforce a maximum file length
+ * @author Alberto Rodríguez
+ */
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+var lodash = require("lodash");
+var astUtils = require("../ast-utils");
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        docs: {
+            description: "enforce a maximum number of lines per file",
+            category: "Stylistic Issues",
+            recommended: false
+        },
+
+        schema: [
+            {
+                oneOf: [
+                    {
+                        type: "integer",
+                        minimum: 0
+                    },
+                    {
+                        type: "object",
+                        properties: {
+                            max: {
+                                type: "integer",
+                                minimum: 0
+                            },
+                            skipComments: {
+                                type: "boolean"
+                            },
+                            skipBlankLines: {
+                                type: "boolean"
+                            }
+                        },
+                        additionalProperties: false
+                    }
+                ]
+            }
+        ]
+    },
+
+    create: function(context) {
+        var option = context.options[0],
+            max = 300;
+
+        if (typeof option === "object" && option.hasOwnProperty("max") && typeof option.max === "number") {
+            max = option.max;
+        }
+
+        if (typeof option === "number") {
+            max = option;
+        }
+
+        var skipComments = option && option.skipComments;
+        var skipBlankLines = option && option.skipBlankLines;
+
+        var sourceCode = context.getSourceCode();
+
+        /**
+         * Returns whether or not a token is a comment node type
+         * @param {Token} token The token to check
+         * @returns {boolean} True if the token is a comment node
+         */
+        function isCommentNodeType(token) {
+            return token && (token.type === "Block" || token.type === "Line");
+        }
+
+        /**
+         * Returns the line numbers of a comment that don't have any code on the same line
+         * @param {Node} comment The comment node to check
+         * @returns {int[]} The line numbers
+         */
+        function getLinesWithoutCode(comment) {
+            var start = comment.loc.start.line;
+            var end = comment.loc.end.line;
+
+            var token;
+
+            token = comment;
+            do {
+                token = sourceCode.getTokenOrCommentBefore(token);
+            } while (isCommentNodeType(token));
+
+            if (token && astUtils.isTokenOnSameLine(token, comment)) {
+                start += 1;
+            }
+
+            token = comment;
+            do {
+                token = sourceCode.getTokenOrCommentAfter(token);
+            } while (isCommentNodeType(token));
+
+            if (token && astUtils.isTokenOnSameLine(comment, token)) {
+                end -= 1;
+            }
+
+            if (start <= end) {
+                return lodash.range(start, end + 1);
+            }
+            return [];
+        }
+
+        return {
+            "Program:exit": function() {
+                var lines = sourceCode.lines.map(function(text, i) {
+                    return { lineNumber: i + 1, text: text };
+                });
+
+                if (skipBlankLines) {
+                    lines = lines.filter(function(l) {
+                        return l.text.trim() !== "";
+                    });
+                }
+
+                if (skipComments) {
+                    var comments = sourceCode.getAllComments();
+
+                    var commentLines = lodash.flatten(comments.map(function(comment) {
+                        return getLinesWithoutCode(comment);
+                    }));
+
+                    lines = lines.filter(function(l) {
+                        return !lodash.includes(commentLines, l.lineNumber);
+                    });
+                }
+
+                if (lines.length > max) {
+                    context.report({
+                        loc: { line: 1, column: 0 },
+                        message: "File must be at most " + max + " lines long"
+                    });
+                }
+            }
+        };
+    }
+};