Fix: ignore MemberExpression in VariableDeclarators (fixes #6795) (#6815

)

Chained properties on objects will typically not be indented as the rule
expects in variable declarations. For now, ignore variable declarations
(as was done in the previous version of ESLint, where all chained
properties were ignored) and possibly revisit later to offer users
opportunity to enforce alignment and/or sensible indentation.

docs/rules/indent.md

@@ -73,7 +73,7 @@ This rule has an object option:
 * `"SwitchCase"` (default: 0) enforces indentation level for `case` clauses in `switch` statements
 * `"VariableDeclarator"` (default: 1) enforces indentation level for `var` declarators; can also take an object to define separate rules for `var`, `let` and `const` declarations.
 * `"outerIIFEBody"` (default: 1) enforces indentation level for file-level IIFEs.
-* `"MemberExpression"` (off by default) enforces indentation level for multi-line property chains
+* `"MemberExpression"` (off by default) enforces indentation level for multi-line property chains (except in variable declarations and assignments)
 
 Level of indentation denotes the multiple of the indent specified. Example:
 
@@ -274,6 +274,10 @@ Examples of **correct** code for this rule with the `2, { "MemberExpression": 1
 foo
   .bar
   .baz();
+
+// Any indentation is permitted in variable declarations and assignments.
+var bip = aardvark.badger
+                  .coyote;
 ```
 
 ## Compatibility

lib/rules/indent.js

@@ -331,19 +331,40 @@ module.exports = {
         }
 
         /**
-         * Returns the VariableDeclarator based on the current node
+         * Returns a parent node of given node based on a specified type
          * if not present then return null
          * @param {ASTNode} node node to examine
+         * @param {string} type type that is being looked for
          * @returns {ASTNode|void} if found then node otherwise null
          */
-        function getVariableDeclaratorNode(node) {
+        function getParentNodeByType(node, type) {
             let parent = node.parent;
 
-            while (parent.type !== "VariableDeclarator" && parent.type !== "Program") {
+            while (parent.type !== type && parent.type !== "Program") {
                 parent = parent.parent;
             }
 
-            return parent.type === "VariableDeclarator" ? parent : null;
+            return parent.type === type ? parent : null;
+        }
+
+        /**
+         * Returns the VariableDeclarator based on the current node
+         * if not present then return null
+         * @param {ASTNode} node node to examine
+         * @returns {ASTNode|void} if found then node otherwise null
+         */
+        function getVariableDeclaratorNode(node) {
+            return getParentNodeByType(node, "VariableDeclarator");
+        }
+
+        /**
+         * Returns the ExpressionStatement based on the current node
+         * if not present then return null
+         * @param {ASTNode} node node to examine
+         * @returns {ASTNode|void} if found then node otherwise null
+         */
+        function getAssignmentExpressionNode(node) {
+            return getParentNodeByType(node, "AssignmentExpression");
         }
 
         /**
@@ -816,6 +837,18 @@ module.exports = {
                     return;
                 }
 
+                // The typical layout of variable declarations and assignments
+                // alter the expectation of correct indentation. Skip them.
+                // TODO: Add appropriate configuration options for variable
+                // declarations and assignments.
+                if (getVariableDeclaratorNode(node)) {
+                    return;
+                }
+
+                if (getAssignmentExpressionNode(node)) {
+                    return;
+                }
+
                 let propertyIndent = getNodeIndent(node) + indentSize * options.MemberExpression;
 
                 let checkNodes = [node.property];

tests/lib/rules/indent.js

@@ -1389,6 +1389,12 @@ ruleTester.run("indent", rule, {
             "    .by" +
             " .default();",
             options: [4]
+        },
+        {
+            code:
+            "foo = bar.baz()\n" +
+            "        .bip();",
+            options: [4, {MemberExpression: 1}]
         }
     ],
     invalid: [