# rules/eslint/closure-types-centralized.eslint.rule.ts

> 44 lines of code and 9 definitions.

Tree: Governance tree
Language: typescript
Canonical: https://banes-lab.com/anatomy/governance#file-governance-rules-eslint-closure-types-centralized-eslint-rule-ts
Source text: https://banes-lab.com/source/governance/rules/eslint/closure-types-centralized.eslint.rule.ts.txt

Listed in [rules/eslint](https://banes-lab.com/api/source/governance/rules/eslint.md), after [rules/eslint/closure-transitive-liveness.eslint.rule.ts](https://banes-lab.com/source/governance/rules/eslint/closure-transitive-liveness.eslint.rule.ts.md) and before [rules/eslint/factory-owned-value.eslint.rule.ts](https://banes-lab.com/source/governance/rules/eslint/factory-owned-value.eslint.rule.ts.md).

## Definitions

- `inTypeBucket` (lexical_declaration, line 14)
- `isTypesFile` (lexical_declaration, line 10)
- `create` (method_definition, line 23, exported)
- `TYPES_CONCERN` (lexical_declaration, line 7)
- `TYPES_SUFFIXES` (lexical_declaration, line 8)
- `path` (lexical_declaration, line 15)
- `{ filename }` (lexical_declaration, line 24, exported)
- `basename` (lexical_declaration, line 25, exported)
- `program` (method_definition, line 30, exported)

## Uses

- [shared/factories/listener.factory.ts](https://banes-lab.com/source/governance/shared/factories/listener.factory.ts.md)
- [shared/manifests/taxonomy.manifest.ts](https://banes-lab.com/source/governance/shared/manifests/taxonomy.manifest.ts.md)
- [shared/resolvers/anchor.resolver.ts](https://banes-lab.com/source/governance/shared/resolvers/anchor.resolver.ts.md)

## Records this file checks

- [Separation of Concerns](https://banes-lab.com/records/architecture/separation-of-concerns.md)

## Source

```typescript
import type { LocalRule, RuleContext, RuleListener } from "../../types/rule.types.ts";
import { basenameOf, isInContainer, normalizePath } from "../../shared/resolvers/anchor.resolver.ts";
import { concernForPath, concernSuffix, isImportedRoot, rootFor } from "../../shared/manifests/taxonomy.manifest.ts";
import { defineCheck } from "@govlab/context/check";
import { listener } from "../../shared/factories/listener.factory.ts";

const TYPES_CONCERN = "types";
const TYPES_SUFFIXES = [concernSuffix(TYPES_CONCERN)];

const isTypesFile = function isTypesFile(basename: string): boolean {
    return TYPES_SUFFIXES.some((suffix) => basename.endsWith(suffix));
};

const inTypeBucket = function inTypeBucket(filename: string): boolean {
    const path = normalizePath(filename);
    if (isImportedRoot(rootFor(path))) {
        return concernForPath(path) === TYPES_CONCERN;
    }
    return isInContainer(filename, TYPES_CONCERN);
};

export default {
    create(context: RuleContext): RuleListener {
        const { filename } = context;
        const basename = basenameOf(filename);
        if (!isTypesFile(basename) || inTypeBucket(filename)) {
            return {};
        }
        return listener({
            program(_view, node) {
                context.report({ data: { basename }, messageId: "misplacedTypesFile", node });
            },
        });
    },
    meta: {
        docs: {
            checks: defineCheck({ detects: [], enforces: ["architecture:separation-of-concerns"] }),
            description:
                "A types file lives in the type bucket its own governed root declares. Type definitions have a change axis of their own — type review, schema evolution, contract audits — separate from the runtime code that happens to use them first, and centralizing the whole surface in one flat bucket is what makes reviewing it as a surface possible. Scattered type files dilute the code files they sit next to and can only be found by searching.",
        },
        messages: {
            misplacedTypesFile:
                "Types file '{{basename}}' sits outside the type bucket its root declares. Move it there — an interface audit, a generic-constraint refactor or a schema migration all need the whole type surface in one flat location.",
        },
        schema: [],
        type: "problem",
    },
} satisfies LocalRule;
```