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Give each template a function scope - #261
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NullVoxPopuli merged 1 commit intoOct 9, 2026
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ESLint's no-use-before-define reports a component that renders itself:
const Foo = <template><Foo /></template>;
class Bar extends Component { <template><Bar /></template> }
It does so even with `{ functions: false, classes: false, variables:
false }` (eslint-config-standard), because it only exempts references from
a separate execution context, and a template's block scope shares its
upper scope's. A template compiles to a closure (`scope: () => ({ Foo })`),
so give it a function scope instead.
On the TypeScript path, FunctionScope declares an implicit `arguments` and
scans the body for a "use strict" directive, which throws on a template's
body when the upper scope isn't strict (a script). A TemplateScope
subclass removes `arguments` and passes `isMethodDefinition` to skip the
scan; the eslint-scope path uses the base Scope, which declares nothing.
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Follow-up to #256. ESLint's own
no-use-before-definereports a component that renders itself:It does this on every release, for
.gjsand.gts, and even with eslint-config-standard's{ functions: false, classes: false, variables: false }. The only way out is turning the rule off. The rule exempts a reference only when it runs in a separate execution context (variable.scope.variableScope !== reference.from.variableScope), and the block scope #256 gives each template shares its upper scope'svariableScope.Fix
A template compiles to a closure (
template(…, { scope: () => ({ Tree }) })), so each template now gets a function scope instead of a block scope. Block params keep their block scopes inside it.TemplateScopesubclass of scope-manager'sFunctionScope.isMethodDefinitionso the scope is strict without the "use strict" directive scan, which throws on a template'sbodywhen the enclosing scope isn't strict (a script, which is also ESLint's default withoutsourceType).argumentsthatFunctionScopedeclares, so{{arguments}}stays undefined.Scopewith typefunction, which declares nothing, with the same strictness argument.Behaviour changes
no-use-before-defineno longer reports a template's reference to its own component (const, class, or static class field), with default or standard options.variables: false, both core and typescript-eslint'sno-use-before-definenow exempt a template reading a variable declared later, as they do for an arrow function. With default options it's still reported.no-varkeeps reporting a loopvarthat a template reads, but no longer autofixes it, as for a closure.require-atomic-updatestreats a variable a template reads as escaping its function, as for a closure.Tests
template scopeintests/parser.test.js, each for.gjs,.gtsand.gjswithuseBabel:no-use-before-defineover const, class and static-field self-references, with default and standard options;{{arguments}}is still reported byno-undef;functiontype, its ownvariableScope, strict, no variables, block-param scopes inside it.test-projects/gts/src/use-before-define.gts(from Stop typescript-eslint's no-use-before-define reporting references in a template assigned to a const #256) now also runs coreno-use-before-define, which Stop typescript-eslint's no-use-before-define reporting references in a template assigned to a const #256 had turned off for it, and gains a class component that renders itself. Onmaincore reports bothTreeandBranch.Also run: the full suite, lint, the test projects, eslint-plugin-ember's suite (
scripts/eslint-plugin-ember-test.mjs), the CI matrix's^6/^7overrides, and a lint comparison against #256's block scope over the repo's 48.gjs/.gtsfiles plus self-reference samples (TS, TS script mode, Babel) with 14 scope-sensitive rules, which differs only in the intendedno-use-before-definereports.