Fix: ignored nodes in indent rule (fixes eslint#9392)

When a node is ignored by the indent rule, it ought not to matter
how it’s indented. But the ignoring of nodes was implemented in
such a way that the *type* of indentation (tabs vs spaces) was
being checked. For example in "tab" mode, an ignored line indented
by four spaces would cause the error “Expected indentation of 4 tabs
but found 4 spaces”.

In particular, this is a problem with “tabs for indentation, spaces
for alignment” styles, where we want to allow code like:

var x = 1,
    y = 2;

where the second line is aligned using four spaces.

This commit marks ignored indents by making them instances of
the IgnoredTokenIndent class, and explicitly ignoring the indentation
of such lines.

All tests pass.

Fixes eslint#9392.

lib/rules/indent.js

@@ -455,6 +455,15 @@ class OffsetStorage {
         }
     }
 
+    /**
+    * Check whether a token is being ignored.
+    * @param {Token} token The token
+    * @returns {boolean} `true` if the token is being ignored
+    */
+    isTokenIgnored(token) {
+        return this._ignoredTokens.has(token);
+    }
+
     /**
      * Gets the first token that the given token's indentation is dependent on
      * @param {Token} token The token
@@ -718,11 +727,16 @@ module.exports = {
         /**
          * Checks if a token's indentation is correct
          * @param {Token} token Token to examine
-         * @param {int} desiredIndentLevel needed indent level
+         * @param {Token} referenceToken Token to use as a reference for the desired indentation
          * @returns {boolean} `true` if the token's indentation is correct
          */
-        function validateTokenIndent(token, desiredIndentLevel) {
+        function validateTokenIndent(token, referenceToken) {
+            if (offsets.isTokenIgnored(token)) {
+                return true;
+            }
+
             const indentation = tokenInfo.getTokenIndent(token);
+            const desiredIndentLevel = offsets.getDesiredIndent(referenceToken);
             const expectedChar = indentType === "space" ? " " : "\t";
 
             return indentation === expectedChar.repeat(desiredIndentLevel * indentSize) ||
@@ -1485,7 +1499,7 @@ module.exports = {
                         }
 
                         // If the token matches the expected expected indentation, don't report it.
-                        if (validateTokenIndent(firstTokenOfLine, offsets.getDesiredIndent(firstTokenOfLine))) {
+                        if (validateTokenIndent(firstTokenOfLine, firstTokenOfLine)) {
                             return;
                         }
 
@@ -1495,8 +1509,8 @@ module.exports = {
 
                             // If a comment matches the expected indentation of the token immediately before or after, don't report it.
                             if (
-                                tokenBefore && validateTokenIndent(firstTokenOfLine, offsets.getDesiredIndent(tokenBefore)) ||
-                                tokenAfter && validateTokenIndent(firstTokenOfLine, offsets.getDesiredIndent(tokenAfter))
+                                tokenBefore && validateTokenIndent(firstTokenOfLine, tokenBefore) ||
+                                tokenAfter && validateTokenIndent(firstTokenOfLine, tokenAfter)
                             ) {
                                 return;
                             }

tests/lib/rules/indent.js

@@ -4744,6 +4744,23 @@ ruleTester.run("indent", rule, {
                 </foo>
             `,
             options: [4, { ignoredNodes: ["JSXOpeningElement"] }]
+        },
+        {
+            code: unIndent`
+                {
+                \tvar x = 1,
+                \t    y = 2;
+                }
+            `,
+            options: ["tab"]
+        },
+        {
+            code: unIndent`
+                var x = 1,
+                    y = 2;
+                var z;
+            `,
+            options: ["tab", { ignoredNodes: ["VariableDeclarator"] }]
         }
     ],