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[eslint] Enhance Rule.NodeListener type #45821

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merged 6 commits into from
Sep 23, 2020
Merged

[eslint] Enhance Rule.NodeListener type #45821

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47d5642
[eslint] Enhance Rule.NodeListener type
acid-chicken Jul 1, 2020
178e839
Add test
acid-chicken Jul 1, 2020
6aa2223
refactor(eslint): unwind Rule.NodeListener
acid-chicken Aug 1, 2020
1475c98
test(eslint): add missing tests
acid-chicken Aug 1, 2020
0909c3e
fix(eslint): add missing import
acid-chicken Aug 1, 2020
3c01315
Merge branch 'master' of https://github.com/DefinitelyTyped/Definitel…
acid-chicken Aug 22, 2020
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3 changes: 2 additions & 1 deletion types/eslint/ts3.1/eslint-tests.ts
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
import { Comment } from 'estree';
import { Comment, WhileStatement } from 'estree';
import { AST, SourceCode, Rule, Linter, ESLint, CLIEngine, RuleTester, Scope } from 'eslint';

const SOURCE = `var foo = bar;`;
Expand Down Expand Up @@ -381,6 +381,7 @@ rule = {
onCodePathSegmentEnd(segment, node) {},
onCodePathSegmentLoop(fromSegment, toSegment, node) {},
IfStatement(node) {},
WhileStatement(node: WhileStatement) {},
'Program:exit'() {},
};
},
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9 changes: 8 additions & 1 deletion types/eslint/ts3.1/index.d.ts
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Expand Up @@ -236,7 +236,13 @@ export namespace Rule {
}

type NodeTypes = ESTree.Node['type'];
type NodeListener = { [T in NodeTypes]?: (node: ESTree.Node) => void };
type NodeListener = ESTree.Node extends infer T
? (T extends ESTree.Node ? (_: { [_ in T['type']]?: (node: T) => void }) => void : never) extends (
_: infer U,
) => void
? U
: never
: never;
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@bradzacher bradzacher Jul 1, 2020 •
edited

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I don't think this kind of conditional logic is a good idea
In my experience, creating types dynamically like this over large sets (ESTree.Node is a union of 70 interfaces with 68 distinct type's) can easily cause OOMs in TS
microsoft/TypeScript#30473

This is evidenced by the above typescript-bot perf check which lists the memory usage as being 25% higher.

When I dumped this into a local repo, vscode's typescript integration paused for a few seconds whilst it computed the types.

The only thing that I've found to work efficiently is to list out every single key manually:
https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/experimental-utils/src/ts-eslint/Rule.ts#L247-L424


interface RuleListener extends NodeListener {
onCodePathStart?(codePath: CodePath, node: ESTree.Node): void;
Expand All @@ -254,6 +260,7 @@ export namespace Rule {
| ((segment: CodePathSegment, node: ESTree.Node) => void)
| ((fromSegment: CodePathSegment, toSegment: CodePathSegment, node: ESTree.Node) => void)
| ((node: ESTree.Node) => void)
| NodeListener[keyof NodeListener]
| undefined;
}

Expand Down