From e972c1939fb36b55bb33d799d2a9dbe7bab3f42d Mon Sep 17 00:00:00 2001
From: Kevin Partington <kevin.partington@kernelpanicstudios.com>
Date: Fri, 5 Oct 2018 14:43:06 -0500
Subject: [PATCH] Update: no-tabs allowIndentationTabs option (fixes #10256)

---
 docs/rules/no-tabs.md      | 28 ++++++++++++++++++++++++----
 lib/rules/no-tabs.js       | 29 +++++++++++++++++++++++------
 tests/lib/rules/no-tabs.js | 32 +++++++++++++++++++++++++-------
 3 files changed, 72 insertions(+), 17 deletions(-)

diff --git a/docs/rules/no-tabs.md b/docs/rules/no-tabs.md
index 691b2f2af2a..4e02d9a04c6 100644
--- a/docs/rules/no-tabs.md
+++ b/docs/rules/no-tabs.md
@@ -9,14 +9,14 @@ This rule looks for tabs anywhere inside a file: code, comments or anything else
 Examples of **incorrect** code for this rule:
 
 ```js
-var a /t= 2;
+var a \t= 2;
 
 /**
-* /t/t it's a test function
+* \t\t it's a test function
 */
 function test(){}
 
-var x = 1; // /t test
+var x = 1; // \t test
 ```
 
 Examples of **correct** code for this rule:
@@ -32,9 +32,29 @@ function test(){}
 var x = 1; // test
 ```
 
+### Options
+
+This rule has an optional object option with the following properties:
+
+* `allowIndentationTabs` (default: false): If this is set to true, then the rule will not report tabs used for indentation.
+
+#### allowIndentationTabs
+
+Examples of **correct** code for this rule with the `allowIndentationTabs: true` option:
+
+```js
+/* eslint no-tabs: ["error", { allowIndentationTabs: true }] */
+
+function test() {
+\tdoSomething();
+}
+
+\t// comment with leading indentation tab
+```
+
 ## When Not To Use It
 
-If you have established a standard where having tabs is fine.
+If you have established a standard where having tabs is fine, then you can disable this rule.
 
 ## Compatibility
 
diff --git a/lib/rules/no-tabs.js b/lib/rules/no-tabs.js
index 08a8fa5b758..c22a94da38b 100644
--- a/lib/rules/no-tabs.js
+++ b/lib/rules/no-tabs.js
@@ -8,7 +8,9 @@
 //------------------------------------------------------------------------------
 // Helpers
 //------------------------------------------------------------------------------
-const regex = /\t/;
+
+const tabRegex = /\t+/g;
+const anyNonWhitespaceRegex = /\S/;
 
 //------------------------------------------------------------------------------
 // Public Interface
@@ -22,21 +24,36 @@ module.exports = {
             recommended: false,
             url: "https://eslint.org/docs/rules/no-tabs"
         },
-        schema: []
+        schema: [{
+            type: "object",
+            properties: {
+                allowIndentationTabs: {
+                    type: "boolean"
+                }
+            },
+            additionalProperties: false
+        }]
     },
 
     create(context) {
+        const sourceCode = context.getSourceCode();
+        const allowIndentationTabs = context.options && context.options[0] && context.options[0].allowIndentationTabs;
+
         return {
             Program(node) {
-                context.getSourceCode().getLines().forEach((line, index) => {
-                    const match = regex.exec(line);
+                sourceCode.getLines().forEach((line, index) => {
+                    let match;
+
+                    while ((match = tabRegex.exec(line)) !== null) {
+                        if (allowIndentationTabs && !anyNonWhitespaceRegex.test(line.slice(0, match.index))) {
+                            continue;
+                        }
 
-                    if (match) {
                         context.report({
                             node,
                             loc: {
                                 line: index + 1,
-                                column: match.index + 1
+                                column: match.index
                             },
                             message: "Unexpected tab character."
                         });
diff --git a/tests/lib/rules/no-tabs.js b/tests/lib/rules/no-tabs.js
index a01d9dc1661..b4989037d30 100644
--- a/tests/lib/rules/no-tabs.js
+++ b/tests/lib/rules/no-tabs.js
@@ -23,7 +23,16 @@ ruleTester.run("no-tabs", rule, {
         "function test(){\n}",
         "function test(){\n" +
         "  //   sdfdsf \n" +
-        "}"
+        "}",
+
+        {
+            code: "\tdoSomething();",
+            options: [{ allowIndentationTabs: true }]
+        },
+        {
+            code: "\t// comment",
+            options: [{ allowIndentationTabs: true }]
+        }
     ],
     invalid: [
         {
@@ -31,7 +40,7 @@ ruleTester.run("no-tabs", rule, {
             errors: [{
                 message: ERROR_MESSAGE,
                 line: 1,
-                column: 18
+                column: 17
             }]
         },
         {
@@ -39,7 +48,7 @@ ruleTester.run("no-tabs", rule, {
             errors: [{
                 message: ERROR_MESSAGE,
                 line: 1,
-                column: 6
+                column: 5
             }]
         },
         {
@@ -50,7 +59,7 @@ ruleTester.run("no-tabs", rule, {
             errors: [{
                 message: ERROR_MESSAGE,
                 line: 2,
-                column: 6
+                column: 5
             }]
         },
         {
@@ -61,7 +70,7 @@ ruleTester.run("no-tabs", rule, {
             errors: [{
                 message: ERROR_MESSAGE,
                 line: 1,
-                column: 10
+                column: 9
             }]
         },
         {
@@ -73,14 +82,23 @@ ruleTester.run("no-tabs", rule, {
                 {
                     message: ERROR_MESSAGE,
                     line: 2,
-                    column: 6
+                    column: 5
                 },
                 {
                     message: ERROR_MESSAGE,
                     line: 3,
-                    column: 2
+                    column: 1
                 }
             ]
+        },
+        {
+            code: "\t// Comment with leading tab \t and inline tab",
+            options: [{ allowIndentationTabs: true }],
+            errors: [{
+                message: ERROR_MESSAGE,
+                line: 1,
+                column: 30
+            }]
         }
     ]
 });