@studnicky/no-redefined-external-types

Requires an exported local interface or type alias to reuse a public type exported by a direct declared dependency instead of rebuilding the same structural shape. The rule resolves every exact public export subpath declared by each direct dependency in the consumer package manifest, including /node, /browser, and neutral type subpaths. It compares only the restricted declaration-level shapes it can prove identical, so a local shape with any additional requirement remains valid composition. Private declarations, undeclared or transitive packages, wildcard-only export paths, dependency internals, and public types outside the restricted declaration syntax are outside its scope.

Fixable: No · Options: No · Suggested severity: error

Performance

Dependency and entity candidates depend only on the linted file's package root, never on the file itself, so SemanticTypeCatalog caches them once per (ts.Program, packageRoot) in a WeakMap instead of rebuilding on every linted file's Program:exit. Platform candidates are excluded from the cache — checker.getSymbolsInScope is genuinely file-scoped, since a file that shadows a global identifier name changes which symbol that name resolves to in that file's own scope.

Measured with TIMING=1 npx eslint packages/eslint-config/src (150 files, one process): this rule's share of total rule-execution time drops from 23287ms (81.4%) to roughly 2400ms (19–28%, depending on run-to-run ordering of the rules table) — an ~89.6% reduction on this corpus. Findings are byte-identical before and after: a full workspace lint reports the same (empty) result, and a synthetic three-file fixture sharing one program and producing real redefined-external-type violations reports the identical messages, lines, and rule IDs.

✗ Incorrect

// @example/contracts exports RequestOptions with retries and timeoutMs.
export interface LocalRequestOptions {
  readonly retries: number;
  readonly timeoutMs: number;
}

// @example/contracts exports Result with value.
export type LocalResult = {
  readonly value: string;
};

The rule resolves public exports from direct dependencies declared in the package manifest; an import is not required for it to detect that the local declarations duplicate RequestOptions and Result.

✓ Correct

import type { RequestOptions } from "@example/contracts";

export interface AuditedRequestOptions extends RequestOptions {
  readonly auditLabel: string;
}

import type { Result } from "@example/contracts";

export type LocalResult = Result;

Use the dependency type directly when no local contract is needed, or compose it into a strictly larger shape when the consumer owns additional requirements.

Canonical entity Type/InputType are exempt as a class

An entity namespace's own Type and InputType members are never reported, even when they structurally coincide with an unrelated dependency's public type. Their shape is authored by this codebase's own schema, not redefined from a library — the redefinition remedy (import the dependency's type, or extend it) is never correct for one, since importing an unrelated package's type into a schema-derived domain model would trade a coincidental structural match for a real, wrong coupling. This exemption is narrow: it requires the same provable schema-derivation provenance type-alias-invariants and entity-file-shape require elsewhere (a verified FromSchema/NodeStaticType/NodeInputType reference owning the namespace's own Schema/Node), not membership in an *Entity namespace alone — a hand-written Type/InputType with no such provenance is still reported.