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/**
* @fileoverview A rule to verify `super()` callings in constructor.
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Checks whether a given code path segment is reachable or not.
*
* @param {CodePathSegment} segment - A code path segment to check.
* @returns {boolean} `true` if the segment is reachable.
*/
function isReachable(segment) {
return segment.reachable;
}
/**
* Checks whether or not a given node is a constructor.
* @param {ASTNode} node - A node to check. This node type is one of
* `Program`, `FunctionDeclaration`, `FunctionExpression`, and
* `ArrowFunctionExpression`.
* @returns {boolean} `true` if the node is a constructor.
*/
function isConstructorFunction(node) {
return (
node.type === "FunctionExpression" &&
node.parent.type === "MethodDefinition" &&
node.parent.kind === "constructor"
);
}
/**
* Checks whether a given node can be a constructor or not.
*
* @param {ASTNode} node - A node to check.
* @returns {boolean} `true` if the node can be a constructor.
*/
function isPossibleConstructor(node) {
if (!node) {
return false;
}
switch (node.type) {
case "ClassExpression":
case "FunctionExpression":
case "ThisExpression":
case "MemberExpression":
case "CallExpression":
case "NewExpression":
case "YieldExpression":
case "TaggedTemplateExpression":
case "MetaProperty":
return true;
case "Identifier":
return node.name !== "undefined";
case "AssignmentExpression":
return isPossibleConstructor(node.right);
case "LogicalExpression":
return (
isPossibleConstructor(node.left) ||
isPossibleConstructor(node.right)
);
case "ConditionalExpression":
return (
isPossibleConstructor(node.alternate) ||
isPossibleConstructor(node.consequent)
);
case "SequenceExpression": {
const lastExpression = node.expressions[node.expressions.length - 1];
return isPossibleConstructor(lastExpression);
}
default:
return false;
}
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
type: "problem",
docs: {
description: "require `super()` calls in constructors",
category: "ECMAScript 6",
recommended: true,
url: "https://eslint.org/docs/rules/constructor-super"
},
schema: [],
messages: {
missingSome: "Lacked a call of 'super()' in some code paths.",
missingAll: "Expected to call 'super()'.",
duplicate: "Unexpected duplicate 'super()'.",
badSuper: "Unexpected 'super()' because 'super' is not a constructor.",
unexpected: "Unexpected 'super()'."
}
},
create(context) {
/*
* {{hasExtends: boolean, scope: Scope, codePath: CodePath}[]}
* Information for each constructor.
* - upper: Information of the upper constructor.
* - hasExtends: A flag which shows whether own class has a valid `extends`
* part.
* - scope: The scope of own class.
* - codePath: The code path object of the constructor.
*/
let funcInfo = null;
/*
* {Map<string, {calledInSomePaths: boolean, calledInEveryPaths: boolean}>}
* Information for each code path segment.
* - calledInSomePaths: A flag of be called `super()` in some code paths.
* - calledInEveryPaths: A flag of be called `super()` in all code paths.
* - validNodes:
*/
let segInfoMap = Object.create(null);
/**
* Gets the flag which shows `super()` is called in some paths.
* @param {CodePathSegment} segment - A code path segment to get.
* @returns {boolean} The flag which shows `super()` is called in some paths
*/
function isCalledInSomePath(segment) {
return segment.reachable && segInfoMap[segment.id].calledInSomePaths;
}
/**
* Gets the flag which shows `super()` is called in all paths.
* @param {CodePathSegment} segment - A code path segment to get.
* @returns {boolean} The flag which shows `super()` is called in all paths.
*/
function isCalledInEveryPath(segment) {
/*
* If specific segment is the looped segment of the current segment,
* skip the segment.
* If not skipped, this never becomes true after a loop.
*/
if (segment.nextSegments.length === 1 &&
segment.nextSegments[0].isLoopedPrevSegment(segment)
) {
return true;
}
return segment.reachable && segInfoMap[segment.id].calledInEveryPaths;
}
return {
/**
* Stacks a constructor information.
* @param {CodePath} codePath - A code path which was started.
* @param {ASTNode} node - The current node.
* @returns {void}
*/
onCodePathStart(codePath, node) {
if (isConstructorFunction(node)) {
// Class > ClassBody > MethodDefinition > FunctionExpression
const classNode = node.parent.parent.parent;
const superClass = classNode.superClass;
funcInfo = {
upper: funcInfo,
isConstructor: true,
hasExtends: Boolean(superClass),
superIsConstructor: isPossibleConstructor(superClass),
codePath
};
} else {
funcInfo = {
upper: funcInfo,
isConstructor: false,
hasExtends: false,
superIsConstructor: false,
codePath
};
}
},
/**
* Pops a constructor information.
* And reports if `super()` lacked.
* @param {CodePath} codePath - A code path which was ended.
* @param {ASTNode} node - The current node.
* @returns {void}
*/
onCodePathEnd(codePath, node) {
const hasExtends = funcInfo.hasExtends;
// Pop.
funcInfo = funcInfo.upper;
if (!hasExtends) {
return;
}
// Reports if `super()` lacked.
const segments = codePath.returnedSegments;
const calledInEveryPaths = segments.every(isCalledInEveryPath);
const calledInSomePaths = segments.some(isCalledInSomePath);
if (!calledInEveryPaths) {
context.report({
messageId: calledInSomePaths
? "missingSome"
: "missingAll",
node: node.parent
});
}
},
/**
* Initialize information of a given code path segment.
* @param {CodePathSegment} segment - A code path segment to initialize.
* @returns {void}
*/
onCodePathSegmentStart(segment) {
if (!(funcInfo && funcInfo.isConstructor && funcInfo.hasExtends)) {
return;
}
// Initialize info.
const info = segInfoMap[segment.id] = {
calledInSomePaths: false,
calledInEveryPaths: false,
validNodes: []
};
// When there are previous segments, aggregates these.
const prevSegments = segment.prevSegments;
if (prevSegments.length > 0) {
info.calledInSomePaths = prevSegments.some(isCalledInSomePath);
info.calledInEveryPaths = prevSegments.every(isCalledInEveryPath);
}
},
/**
* Update information of the code path segment when a code path was
* looped.
* @param {CodePathSegment} fromSegment - The code path segment of the
* end of a loop.
* @param {CodePathSegment} toSegment - A code path segment of the head
* of a loop.
* @returns {void}
*/
onCodePathSegmentLoop(fromSegment, toSegment) {
if (!(funcInfo && funcInfo.isConstructor && funcInfo.hasExtends)) {
return;
}
// Update information inside of the loop.
const isRealLoop = toSegment.prevSegments.length >= 2;
funcInfo.codePath.traverseSegments(
{ first: toSegment, last: fromSegment },
segment => {
const info = segInfoMap[segment.id];
const prevSegments = segment.prevSegments;
// Updates flags.
info.calledInSomePaths = prevSegments.some(isCalledInSomePath);
info.calledInEveryPaths = prevSegments.every(isCalledInEveryPath);
// If flags become true anew, reports the valid nodes.
if (info.calledInSomePaths || isRealLoop) {
const nodes = info.validNodes;
info.validNodes = [];
for (let i = 0; i < nodes.length; ++i) {
const node = nodes[i];
context.report({
messageId: "duplicate",
node
});
}
}
}
);
},
/**
* Checks for a call of `super()`.
* @param {ASTNode} node - A CallExpression node to check.
* @returns {void}
*/
"CallExpression:exit"(node) {
if (!(funcInfo && funcInfo.isConstructor)) {
return;
}
// Skips except `super()`.
if (node.callee.type !== "Super") {
return;
}
// Reports if needed.
if (funcInfo.hasExtends) {
const segments = funcInfo.codePath.currentSegments;
let duplicate = false;
let info = null;
for (let i = 0; i < segments.length; ++i) {
const segment = segments[i];
if (segment.reachable) {
info = segInfoMap[segment.id];
duplicate = duplicate || info.calledInSomePaths;
info.calledInSomePaths = info.calledInEveryPaths = true;
}
}
if (info) {
if (duplicate) {
context.report({
messageId: "duplicate",
node
});
} else if (!funcInfo.superIsConstructor) {
context.report({
messageId: "badSuper",
node
});
} else {
info.validNodes.push(node);
}
}
} else if (funcInfo.codePath.currentSegments.some(isReachable)) {
context.report({
messageId: "unexpected",
node
});
}
},
/**
* Set the mark to the returned path as `super()` was called.
* @param {ASTNode} node - A ReturnStatement node to check.
* @returns {void}
*/
ReturnStatement(node) {
if (!(funcInfo && funcInfo.isConstructor && funcInfo.hasExtends)) {
return;
}
// Skips if no argument.
if (!node.argument) {
return;
}
// Returning argument is a substitute of 'super()'.
const segments = funcInfo.codePath.currentSegments;
for (let i = 0; i < segments.length; ++i) {
const segment = segments[i];
if (segment.reachable) {
const info = segInfoMap[segment.id];
info.calledInSomePaths = info.calledInEveryPaths = true;
}
}
},
/**
* Resets state.
* @returns {void}
*/
"Program:exit"() {
segInfoMap = Object.create(null);
}
};
}
};
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