feat(ts): implement unnecessaryConstructors rule#2953
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…ypescript-eslint Verbatim copy of typescript-eslint/typescript-eslint@4ba3e02 (rule, tests, docs) as the starting point for the flint unnecessaryConstructors port. Subsequent commits adapt it to flint; diff them to see exactly what the port changed. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Stage 2 of the port: reshape the upstream files to flint's rule/test/docs conventions (ruleCreator, .ts specifiers, rule-tester format, mdx frontmatter) before the full implementation pass. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Ports @typescript-eslint/no-useless-constructor (merging its ESLint-core base-rule logic) to flint's ruleCreator/services API. Includes rule, tests, docs, comparisons status, and a changeset. fixes flint-fyi#2226 Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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PR Checklist
status: accepting prsOverview
Implements
ts/unnecessaryConstructors, the flint equivalent of@typescript-eslint/no-useless-constructor.Reports constructors that are equivalent to the implicit default constructor — an empty constructor in a base class, or a derived-class constructor that only forwards its parameters to
super— with a suggestion to remove them.Provenance (staged commits)
Ported from typescript-eslint/typescript-eslint@4ba3e02e (75 LOC):
Diff commits 1→3 to see exactly what the port changed.
Note on sources: the upstream rule is an extension rule that delegates its core logic to ESLint core's
no-useless-constructorviagetESLintCoreRule. Since flint rules are self-contained, this port merges the core semantics and the TS-specific exemptions (accessibility modifiers, parameter properties, parameter decorators) into one rule; both upstream test suites were used as the edge-case reference.Behavior vs upstream
constructor(...[a, b]) { super(...arguments); }): ESLint core treats any rest element as "simple" and reports; this port requires the rest parameter to be a plain identifier and does not report. Removing such a constructor can change behavior (pattern defaults may have side effects), so the port takes the safe direction.needsPrecedingSemicolonmachinery to decide whether removing the constructor needs a separating;; this port uses class-member-shaped checks (previous member ends in an unterminated initializer, next member begins with[/*/in/instanceof). Output is identical across core's suggestion test matrix (all ported); the only known delta inserts a harmless extra;in one TS-specific corner.removeConstructorsuggestion is ported as a real flint suggestion, not dropped.Everything else is behavior parity, including: overload signatures / ambient declarations never flagged,
implements-only classes treated as base classes,'constructor'()string-key form flagged, and parentheses skipped at all expression positions.A courtesy note: rule naming for the
unnecessary*family is under discussion in #2802 — happy to rename if that lands on a different convention.Files
packages/ts/src/rules/unnecessaryConstructors.ts— the rule (self-contained port)packages/ts/src/rules/unnecessaryConstructors.test.ts— 25 invalid cases (snapshot + suggestion output each) + 43 valid casespackages/site/src/content/docs/rules/ts/unnecessaryConstructors.mdx— full rule docpackages/ts/src/plugin.ts— rule registered alphabeticallypackages/comparisons/src/data.json— existing entry marked"status": "implemented".changeset/unnecessary-constructors.md— patch changesetLocal gates
eslint --max-warnings 0·tsc -b packages/ts·vitest(rule test, 68 passing) ·vitest(comparisons) ·prettier --check— all pass locally.🤖 Generated with Claude Code