84 lines
2.6 KiB
JavaScript
84 lines
2.6 KiB
JavaScript
/**
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* @fileoverview Rule to disallow uses of await inside of loops.
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* @author Nat Mote (nmote)
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*/
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"use strict";
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// Node types which are considered loops.
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const loopTypes = new Set([
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"ForStatement",
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"ForOfStatement",
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"ForInStatement",
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"WhileStatement",
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"DoWhileStatement"
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]);
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/*
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* Node types at which we should stop looking for loops. For example, it is fine to declare an async
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* function within a loop, and use await inside of that.
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*/
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const boundaryTypes = new Set([
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"FunctionDeclaration",
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"FunctionExpression",
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"ArrowFunctionExpression"
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]);
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module.exports = {
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meta: {
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docs: {
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description: "disallow `await` inside of loops",
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category: "Possible Errors",
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recommended: false
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},
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schema: []
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},
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create(context) {
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return {
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AwaitExpression(node) {
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const ancestors = context.getAncestors();
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// Reverse so that we can traverse from the deepest node upwards.
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ancestors.reverse();
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/*
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* Create a set of all the ancestors plus this node so that we can check
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* if this use of await appears in the body of the loop as opposed to
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* the right-hand side of a for...of, for example.
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*/
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const ancestorSet = new Set(ancestors).add(node);
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for (let i = 0; i < ancestors.length; i++) {
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const ancestor = ancestors[i];
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if (boundaryTypes.has(ancestor.type)) {
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/*
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* Short-circuit out if we encounter a boundary type. Loops above
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* this do not matter.
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*/
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return;
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}
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if (loopTypes.has(ancestor.type)) {
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/*
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* Only report if we are actually in the body or another part that gets executed on
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* every iteration.
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*/
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if (
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ancestorSet.has(ancestor.body) ||
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ancestorSet.has(ancestor.test) ||
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ancestorSet.has(ancestor.update)
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) {
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context.report({
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node,
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message: "Unexpected `await` inside a loop."
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});
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return;
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}
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}
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}
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}
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};
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}
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};
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