Update: optional chaining support (fixes #12642)

lib/linter/code-path-analysis/code-path-analyzer.js

@@ -244,6 +244,19 @@ function preprocess(analyzer, node) {
     const parent = node.parent;
 
     switch (parent.type) {
+
+        // The `arguments.length == 0` case is in `postprocess` function.
+        case "CallExpression":
+            if (parent.optional === true && parent.arguments.length >= 1 && parent.arguments[0] === node) {
+                state.makeOptionalRight();
+            }
+            break;
+        case "MemberExpression":
+            if (parent.optional === true && parent.property === node) {
+                state.makeOptionalRight();
+            }
+            break;
+
         case "LogicalExpression":
             if (
                 parent.right === node &&
@@ -377,6 +390,20 @@ function processCodePathToEnter(analyzer, node) {
             analyzer.emitter.emit("onCodePathStart", codePath, node);
             break;
 
+        case "ChainExpression":
+            state.pushChainContext();
+            break;
+        case "CallExpression":
+            if (node.optional === true) {
+                state.makeOptionalNode();
+            }
+            break;
+        case "MemberExpression":
+            if (node.optional === true) {
+                state.makeOptionalNode();
+            }
+            break;
+
         case "LogicalExpression":
             if (isHandledLogicalOperator(node.operator)) {
                 state.pushChoiceContext(
@@ -449,6 +476,10 @@ function processCodePathToExit(analyzer, node) {
     let dontForward = false;
 
     switch (node.type) {
+        case "ChainExpression":
+            state.popChainContext();
+            break;
+
         case "IfStatement":
         case "ConditionalExpression":
             state.popChoiceContext();
@@ -583,6 +614,13 @@ function postprocess(analyzer, node) {
             break;
         }
 
+        // The `arguments.length >= 1` case is in `preprocess` function.
+        case "CallExpression":
+            if (node.optional === true && node.arguments.length === 0) {
+                CodePath.getState(analyzer.codePath).makeOptionalRight();
+            }
+            break;
+
         default:
             break;
     }

lib/linter/code-path-analysis/code-path-segment.js

@@ -92,7 +92,6 @@ class CodePathSegment {
         /* istanbul ignore if */
         if (debug.enabled) {
             this.internal.nodes = [];
-            this.internal.exitNodes = [];
         }
     }
 

lib/linter/code-path-analysis/code-path-state.js

@@ -234,6 +234,7 @@ class CodePathState {
         this.tryContext = null;
         this.loopContext = null;
         this.breakContext = null;
+        this.chainContext = null;
 
         this.currentSegments = [];
         this.initialSegment = this.forkContext.head[0];
@@ -555,6 +556,64 @@ class CodePathState {
         );
     }
 
+    //--------------------------------------------------------------------------
+    // ChainExpression
+    //--------------------------------------------------------------------------
+
+    /**
+     * Push a new `ChainExpression` context to the stack.
+     * This method is called on entering to each `ChainExpression` node.
+     * This context is used to count forking in the optional chain then merge them on the exiting from the `ChainExpression` node.
+     * @returns {void}
+     */
+    pushChainContext() {
+        this.chainContext = {
+            upper: this.chainContext,
+            countChoiceContexts: 0
+        };
+    }
+
+    /**
+     * Pop a `ChainExpression` context from the stack.
+     * This method is called on exiting from each `ChainExpression` node.
+     * This merges all forks of the last optional chaining.
+     * @returns {void}
+     */
+    popChainContext() {
+        const context = this.chainContext;
+
+        this.chainContext = context.upper;
+
+        // pop all choice contexts of this.
+        for (let i = context.countChoiceContexts; i > 0; --i) {
+            this.popChoiceContext();
+        }
+    }
+
+    /**
+     * Create a choice context for optional access.
+     * This method is called on entering to each `(Call|Member)Expression[optional=true]` node.
+     * This creates a choice context as similar to `LogicalExpression[operator="??"]` node.
+     * @returns {void}
+     */
+    makeOptionalNode() {
+        if (this.chainContext) {
+            this.chainContext.countChoiceContexts += 1;
+            this.pushChoiceContext("??", false);
+        }
+    }
+
+    /**
+     * Create a fork.
+     * This method is called on entering to the `arguments|property` property of each `(Call|Member)Expression` node.
+     * @returns {void}
+     */
+    makeOptionalRight() {
+        if (this.chainContext) {
+            this.makeLogicalRight();
+        }
+    }
+
     //--------------------------------------------------------------------------
     // SwitchStatement
     //--------------------------------------------------------------------------

lib/linter/code-path-analysis/debug-helpers.js

@@ -25,6 +25,22 @@ function getId(segment) { // eslint-disable-line jsdoc/require-jsdoc
     return segment.id + (segment.reachable ? "" : "!");
 }
 
+/**
+ * Get string for the given node and operation.
+ * @param {ASTNode} node The node to convert.
+ * @param {"enter" | "exit" | undefined} label The operation label.
+ * @returns {string} The string representation.
+ */
+function nodeToString(node, label) {
+    const suffix = label ? `:${label}` : "";
+
+    switch (node.type) {
+        case "Identifier": return `${node.type}${suffix} (${node.name})`;
+        case "Literal": return `${node.type}${suffix} (${node.value})`;
+        default: return `${node.type}${suffix}`;
+    }
+}
+
 //------------------------------------------------------------------------------
 // Public Interface
 //------------------------------------------------------------------------------
@@ -56,9 +72,15 @@ module.exports = {
             const segInternal = state.currentSegments[i].internal;
 
             if (leaving) {
-                segInternal.exitNodes.push(node);
+                const last = segInternal.nodes.length - 1;
+
+                if (last >= 0 && segInternal.nodes[last] === nodeToString(node, "enter")) {
+                    segInternal.nodes[last] = nodeToString(node, void 0);
+                } else {
+                    segInternal.nodes.push(nodeToString(node, "exit"));
+                }
             } else {
-                segInternal.nodes.push(node);
+                segInternal.nodes.push(nodeToString(node, "enter"));
             }
         }
 
@@ -104,23 +126,8 @@ module.exports = {
                 text += "style=\"rounded,dashed,filled\",fillcolor=\"#FF9800\",label=\"<<unreachable>>\\n";
             }
 
-            if (segment.internal.nodes.length > 0 || segment.internal.exitNodes.length > 0) {
-                text += [].concat(
-                    segment.internal.nodes.map(node => {
-                        switch (node.type) {
-                            case "Identifier": return `${node.type} (${node.name})`;
-                            case "Literal": return `${node.type} (${node.value})`;
-                            default: return node.type;
-                        }
-                    }),
-                    segment.internal.exitNodes.map(node => {
-                        switch (node.type) {
-                            case "Identifier": return `${node.type}:exit (${node.name})`;
-                            case "Literal": return `${node.type}:exit (${node.value})`;
-                            default: return `${node.type}:exit`;
-                        }
-                    })
-                ).join("\\n");
+            if (segment.internal.nodes.length > 0) {
+                text += segment.internal.nodes.join("\\n");
             } else {
                 text += "????";
             }

lib/rules/accessor-pairs.js

@@ -86,16 +86,6 @@ function isAccessorKind(node) {
     return node.kind === "get" || node.kind === "set";
 }
 
-/**
- * Checks whether or not a given node is an `Identifier` node which was named a given name.
- * @param {ASTNode} node A node to check.
- * @param {string} name An expected name of the node.
- * @returns {boolean} `true` if the node is an `Identifier` node which was named as expected.
- */
-function isIdentifier(node, name) {
-    return node.type === "Identifier" && node.name === name;
-}
-
 /**
  * Checks whether or not a given node is an argument of a specified method call.
  * @param {ASTNode} node A node to check.
@@ -109,10 +99,7 @@ function isArgumentOfMethodCall(node, index, object, property) {
 
     return (
         parent.type === "CallExpression" &&
-        parent.callee.type === "MemberExpression" &&
-        parent.callee.computed === false &&
-        isIdentifier(parent.callee.object, object) &&
-        isIdentifier(parent.callee.property, property) &&
+        astUtils.isSpecificMemberAccess(parent.callee, object, property) &&
         parent.arguments[index] === node
     );
 }

lib/rules/array-callback-return.js

@@ -28,17 +28,14 @@ function isReachable(segment) {
 }
 
 /**
- * Checks a given node is a MemberExpression node which has the specified name's
+ * Checks a given node is a member access which has the specified name's
  * property.
  * @param {ASTNode} node A node to check.
- * @returns {boolean} `true` if the node is a MemberExpression node which has
- *      the specified name's property
+ * @returns {boolean} `true` if the node is a member access which has
+ *      the specified name's property. The node may be a `(Chain|Member)Expression` node.
  */
 function isTargetMethod(node) {
-    return (
-        node.type === "MemberExpression" &&
-        TARGET_METHODS.test(astUtils.getStaticPropertyName(node) || "")
-    );
+    return astUtils.isSpecificMemberAccess(node, null, TARGET_METHODS);
 }
 
 /**
@@ -76,6 +73,7 @@ function getArrayMethodName(node) {
              */
             case "LogicalExpression":
             case "ConditionalExpression":
+            case "ChainExpression":
                 currentNode = parent;
                 break;
 

lib/rules/consistent-return.js

@@ -9,23 +9,12 @@
 //------------------------------------------------------------------------------
 
 const lodash = require("lodash");
-
 const astUtils = require("./utils/ast-utils");
 
 //------------------------------------------------------------------------------
 // Helpers
 //------------------------------------------------------------------------------
 
-/**
- * Checks whether or not a given node is an `Identifier` node which was named a given name.
- * @param {ASTNode} node A node to check.
- * @param {string} name An expected name of the node.
- * @returns {boolean} `true` if the node is an `Identifier` node which was named as expected.
- */
-function isIdentifier(node, name) {
-    return node.type === "Identifier" && node.name === name;
-}
-
 /**
  * Checks whether or not a given code path segment is unreachable.
  * @param {CodePathSegment} segment A CodePathSegment to check.
@@ -165,7 +154,7 @@ module.exports = {
                 let hasReturnValue = Boolean(argument);
 
                 if (treatUndefinedAsUnspecified && hasReturnValue) {
-                    hasReturnValue = !isIdentifier(argument, "undefined") && argument.operator !== "void";
+                    hasReturnValue = !astUtils.isSpecificId(argument, "undefined") && argument.operator !== "void";
                 }
 
                 if (!funcInfo.hasReturn) {

lib/rules/constructor-super.js

@@ -50,6 +50,7 @@ function isPossibleConstructor(node) {
         case "MemberExpression":
         case "CallExpression":
         case "NewExpression":
+        case "ChainExpression":
         case "YieldExpression":
         case "TaggedTemplateExpression":
         case "MetaProperty":

lib/rules/dot-location.js

@@ -52,31 +52,37 @@ module.exports = {
          */
         function checkDotLocation(node) {
             const property = node.property;
-            const dot = sourceCode.getTokenBefore(property);
-
-            // `obj` expression can be parenthesized, but those paren tokens are not a part of the `obj` node.
-            const tokenBeforeDot = sourceCode.getTokenBefore(dot);
-
-            const textBeforeDot = sourceCode.getText().slice(tokenBeforeDot.range[1], dot.range[0]);
-            const textAfterDot = sourceCode.getText().slice(dot.range[1], property.range[0]);
+            const dotToken = sourceCode.getTokenBefore(property);
 
             if (onObject) {
-                if (!astUtils.isTokenOnSameLine(tokenBeforeDot, dot)) {
-                    const neededTextAfterToken = astUtils.isDecimalIntegerNumericToken(tokenBeforeDot) ? " " : "";
 
+                // `obj` expression can be parenthesized, but those paren tokens are not a part of the `obj` node.
+                const tokenBeforeDot = sourceCode.getTokenBefore(dotToken);
+
+                if (!astUtils.isTokenOnSameLine(tokenBeforeDot, dotToken)) {
                     context.report({
                         node,
-                        loc: dot.loc,
+                        loc: dotToken.loc,
                         messageId: "expectedDotAfterObject",
-                        fix: fixer => fixer.replaceTextRange([tokenBeforeDot.range[1], property.range[0]], `${neededTextAfterToken}.${textBeforeDot}${textAfterDot}`)
+                        *fix(fixer) {
+                            if (dotToken.value.startsWith(".") && astUtils.isDecimalIntegerNumericToken(tokenBeforeDot)) {
+                                yield fixer.insertTextAfter(tokenBeforeDot, ` ${dotToken.value}`);
+                            } else {
+                                yield fixer.insertTextAfter(tokenBeforeDot, dotToken.value);
+                            }
+                            yield fixer.remove(dotToken);
+                        }
                     });
                 }
-            } else if (!astUtils.isTokenOnSameLine(dot, property)) {
+            } else if (!astUtils.isTokenOnSameLine(dotToken, property)) {
                 context.report({
                     node,
-                    loc: dot.loc,
+                    loc: dotToken.loc,
                     messageId: "expectedDotBeforeProperty",
-                    fix: fixer => fixer.replaceTextRange([tokenBeforeDot.range[1], property.range[0]], `${textBeforeDot}${textAfterDot}.`)
+                    *fix(fixer) {
+                        yield fixer.remove(dotToken);
+                        yield fixer.insertTextBefore(property, dotToken.value);
+                    }
                 });
             }
         }