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fix(eslint): gate replaceWithGetErrorMessage suggestion on hasResolvableLocalBinding in no-err-stack-then-string-fallback #49501

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Merged
pelikhan merged 5 commits into from
Aug 1, 2026
+99 −20
Merged

fix(eslint): gate replaceWithGetErrorMessage suggestion on hasResolvableLocalBinding in no-err-stack-then-string-fallback #49501

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ca557e1
Initial plan
Copilot Aug 1, 2026
559aa1d
initial plan
Copilot Aug 1, 2026
af25889
fix(eslint): add hasResolvableLocalBinding guard to no-err-stack-then…
Copilot Aug 1, 2026
1ec7ab3
Merge branch 'main' into copilot/fix-no-err-stack-then-string-fallback
pelikhan Aug 1, 2026
f12e082
fix(eslint): reject variable definitions in TDZ in isDefinitionAvaila…
Copilot Aug 1, 2026
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66 changes: 56 additions & 10 deletions eslint-factory/src/rules/no-err-stack-then-string-fallback.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,7 @@ describe("no-err-stack-then-string-fallback", () => {
valid: [],
invalid: [
{
code: `const msg = err instanceof Error ? err.stack : String(err);`,
code: `const { getErrorMessage } = require("./error_helpers.cjs"); const msg = err instanceof Error ? err.stack : String(err);`,
errors: [
{
messageId: "preferGetErrorMessage",
Expand All @@ -73,7 +73,7 @@ describe("no-err-stack-then-string-fallback", () => {
{
messageId: "replaceWithGetErrorMessage",
data: { errorVar: "err" },
output: `const msg = getErrorMessage(err);`,
output: `const { getErrorMessage } = require("./error_helpers.cjs"); const msg = getErrorMessage(err);`,
},
],
},
Expand All @@ -88,7 +88,7 @@ describe("no-err-stack-then-string-fallback", () => {
valid: [],
invalid: [
{
code: "core.setFailed(`unhandled error: ${err instanceof Error ? err.stack : String(err)}`);",
code: `const { getErrorMessage } = require("./error_helpers.cjs"); core.setFailed(\`unhandled error: \${err instanceof Error ? err.stack : String(err)}\`);`,
errors: [
{
messageId: "preferGetErrorMessage",
Expand All @@ -97,7 +97,7 @@ describe("no-err-stack-then-string-fallback", () => {
{
messageId: "replaceWithGetErrorMessage",
data: { errorVar: "err" },
output: "core.setFailed(`unhandled error: ${getErrorMessage(err)}`);",
output: `const { getErrorMessage } = require("./error_helpers.cjs"); core.setFailed(\`unhandled error: \${getErrorMessage(err)}\`);`,
},
],
},
Expand All @@ -119,7 +119,7 @@ describe("no-err-stack-then-string-fallback", () => {
valid: [],
invalid: [
{
code: `core.setFailed(err && err.stack ? err.stack : String(err));`,
code: `const { getErrorMessage } = require("./error_helpers.cjs"); core.setFailed(err && err.stack ? err.stack : String(err));`,
errors: [
{
messageId: "preferGetErrorMessage",
Expand All @@ -128,7 +128,7 @@ describe("no-err-stack-then-string-fallback", () => {
{
messageId: "replaceWithGetErrorMessage",
data: { errorVar: "err" },
output: `core.setFailed(getErrorMessage(err));`,
output: `const { getErrorMessage } = require("./error_helpers.cjs"); core.setFailed(getErrorMessage(err));`,
},
],
},
Expand All @@ -143,7 +143,7 @@ describe("no-err-stack-then-string-fallback", () => {
valid: [],
invalid: [
{
code: `const msg = err && err.stack ? err.stack : String(err);`,
code: `const { getErrorMessage } = require("./error_helpers.cjs"); const msg = err && err.stack ? err.stack : String(err);`,
errors: [
{
messageId: "preferGetErrorMessage",
Expand All @@ -152,7 +152,7 @@ describe("no-err-stack-then-string-fallback", () => {
{
messageId: "replaceWithGetErrorMessage",
data: { errorVar: "err" },
output: `const msg = getErrorMessage(err);`,
output: `const { getErrorMessage } = require("./error_helpers.cjs"); const msg = getErrorMessage(err);`,
},
],
},
Expand All @@ -167,7 +167,7 @@ describe("no-err-stack-then-string-fallback", () => {
valid: [],
invalid: [
{
code: `console.error(error && error.stack ? error.stack : String(error));`,
code: `const { getErrorMessage } = require("./error_helpers.cjs"); console.error(error && error.stack ? error.stack : String(error));`,
errors: [
{
messageId: "preferGetErrorMessage",
Expand All @@ -176,7 +176,7 @@ describe("no-err-stack-then-string-fallback", () => {
{
messageId: "replaceWithGetErrorMessage",
data: { errorVar: "error" },
output: `console.error(getErrorMessage(error));`,
output: `const { getErrorMessage } = require("./error_helpers.cjs"); console.error(getErrorMessage(error));`,
},
],
},
Expand All @@ -185,4 +185,50 @@ describe("no-err-stack-then-string-fallback", () => {
],
});
});

it("invalid: getErrorMessage defined in its own initializer (TDZ) — diagnostic fires but no suggestion offered", () => {
cjsRuleTester.run("no-err-stack-then-string-fallback", noErrStackThenStringFallbackRule, {
valid: [],
invalid: [
{
code: `const getErrorMessage = err instanceof Error ? err.stack : String(err);`,
errors: [
{
messageId: "preferGetErrorMessage",
data: { errorVar: "err" },
suggestions: [],
},
],
},
],
});
});

it("invalid: no getErrorMessage in scope — diagnostic fires but no suggestion offered", () => {
cjsRuleTester.run("no-err-stack-then-string-fallback", noErrStackThenStringFallbackRule, {
valid: [],
invalid: [
{
code: `const msg = err instanceof Error ? err.stack : String(err);`,
errors: [
{
messageId: "preferGetErrorMessage",
data: { errorVar: "err" },
suggestions: [],
},
],
},
{
code: `process.stderr.write(\`[copilot-sdk-driver] unhandled error: \${err instanceof Error ? err.stack : String(err)}\\n\`);`,
errors: [
{
messageId: "preferGetErrorMessage",
data: { errorVar: "err" },
suggestions: [],
},
],
},
],
});
});
});

@github-actions github-actions Bot Aug 1, 2026

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[/tdd] Tests only cover the CJS require path — the ESM ImportBinding branch of isDefinitionAvailableAtNode is untested.

isDefinitionAvailableAtNode returns true immediately for ImportBinding, so the suggestion will fire for ESM imports too. Adding one test case with import { getErrorMessage } from '...' would confirm that branch and prevent a silent regression if the early-return is removed.

💡 Suggested test snippet 
{
  code: `import { getErrorMessage } from './error_helpers.cjs'; const msg = err instanceof Error ? err.stack : String(err);`,
  errors: [{
    messageId: 'preferGetErrorMessage',
    data: { errorVar: 'err' },
    suggestions: [{ messageId: 'replaceWithGetErrorMessage', data: { errorVar: 'err' }, output: `import { getErrorMessage } from './error_helpers.cjs'; const msg = getErrorMessage(err);` }],
  }],
}

Use an ESM rule tester instance with { parserOptions: { sourceType: 'module' } }.

@copilot please address this.

53 changes: 43 additions & 10 deletions eslint-factory/src/rules/no-err-stack-then-string-fallback.ts
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
import { AST_NODE_TYPES, ESLintUtils, TSESTree } from "@typescript-eslint/utils";
import { AST_NODE_TYPES, ESLintUtils, TSESLint, TSESTree } from "@typescript-eslint/utils";

const createRule = ESLintUtils.RuleCreator(name => `https://github.com/github/gh-aw/tree/main/eslint-factory#${name}`);

Expand Down Expand Up @@ -43,6 +43,22 @@ function isStringErr(node: TSESTree.Node, errVar: string): boolean {
return isIdentifierNamed(node.arguments[0], errVar);
}

function isDefinitionAvailableAtNode(definition: TSESLint.Scope.Definition, node: TSESTree.Node): boolean {
if (definition.type === "ImportBinding" || definition.type === "FunctionName") {
return true;
}
const definitionNode = definition.name ?? definition.node;
if (!definitionNode?.range || !node.range) return false;
if (definitionNode.range[0] >= node.range[0]) return false;
// If the node falls inside the variable declarator's range, the binding is in the
// temporal dead zone at that point (e.g. `const getErrorMessage = <node>`).
const declNode = definition.node;
if (declNode?.range && node.range[0] >= declNode.range[0] && node.range[1] <= declNode.range[1]) {
return false;
}
return true;
}

export const noErrStackThenStringFallbackRule = createRule({
name: "no-err-stack-then-string-fallback",
meta: {
Expand All @@ -63,6 +79,21 @@ export const noErrStackThenStringFallbackRule = createRule({
},
defaultOptions: [],
create(context) {
const sourceCode = context.sourceCode;
type SourceCodeScope = ReturnType<typeof sourceCode.getScope>;

function hasResolvableLocalBinding(node: TSESTree.Node, name: string): boolean {
let scope: SourceCodeScope | null = sourceCode.getScope(node);
while (scope) {
const variable = scope.set.get(name);
if (variable && variable.defs.some(def => isDefinitionAvailableAtNode(def, node))) {
return true;
}
scope = scope.upper;
}
return false;
}

return {
ConditionalExpression(node) {
// Patterns:
Expand Down Expand Up @@ -91,15 +122,17 @@ export const noErrStackThenStringFallbackRule = createRule({
node,
messageId: "preferGetErrorMessage",
data: { errorVar: errVar },
suggest: [
{
messageId: "replaceWithGetErrorMessage",
data: { errorVar: errVar },
fix(fixer) {
return fixer.replaceText(node, `getErrorMessage(${errVar})`);
},
},
],
suggest: hasResolvableLocalBinding(node, "getErrorMessage")
? [
{
messageId: "replaceWithGetErrorMessage",
data: { errorVar: errVar },
fix(fixer) {
return fixer.replaceText(node, `getErrorMessage(${errVar})`);
},
},
]
: [],
});
},
};
Expand Down
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