dev_patterns

Analyze coding patterns in a file against similar code in the codebase. Compares import style, error handling, type coverage, test coverage, and file size.

Not for finding code (use dev_search) or tracing calls (use dev_refs).

Usage


dev_patterns(filePath, format?, limit?)

Parameters

Parameter	Type	Default	Description
`filePath`	string	required	File path to analyze (e.g., `src/auth/middleware.ts`)
`format`	`"compact"` \| `"verbose"` \| `"json"`	`"compact"`	Output format
`limit`	number	10	Maximum similar files to analyze

What It Does

dev_patterns performs comprehensive file analysis in two steps:

Finds similar files — Uses semantic search to find code with similar structure/purpose
Analyzes patterns — Compares error handling, type coverage, imports, testing, and file size

Examples

Basic Inspection

“Use dev_patterns with filePath ‘src/auth/middleware.ts‘“


## File Inspection: src/auth/middleware.ts

### Similar Files (5 analyzed)
1. `src/auth/session.ts` (78%)
2. `src/middleware/logger.ts` (72%)
3. `src/api/auth-handler.ts` (68%)

### Pattern Analysis

**Import Style:** Your file uses `esm`, matching 100% of similar files.
**Error Handling:** Your file uses `throw`, but 60% of similar files use `result`.
**Type Coverage:** Your file has `full` type coverage, matching 80% of similar files.
**Testing:** No test file found. 40% of similar files have tests.
**Size:** 234 lines (smaller than average of 312 lines)

Verbose Output

“Use dev_patterns with filePath ‘packages/core/src/indexer/index.ts’, format ‘verbose’”

Returns detailed pattern distribution and statistics for each pattern category.

JSON Output (Token-Efficient)

“Use dev_patterns with filePath ‘src/auth/middleware.ts’, format ‘json’”

Returns structured JSON — compact and machine-parseable for agent workflows:


{
  "fileSize": { "yourFile": 234, "average": 312, "deviation": "smaller" },
  "importStyle": { "yourFile": "esm", "common": "esm", "percentage": 100 },
  "errorHandling": { "yourFile": "throw", "common": "result", "percentage": 60 },
  "typeAnnotations": { "yourFile": "full", "common": "full", "percentage": 80 },
  "testing": { "yourFile": false, "percentage": 40 }
}

Pattern Categories

Pattern	What It Checks
Import Style	`esm`, `cjs`, `mixed`, or `unknown`
Error Handling	`throw`, `result`, `error-return`, or `unknown`
Type Coverage	`full`, `partial`, `minimal`, or `none` (TypeScript only)
Testing	Whether a co-located test file exists
File Size	Line count vs. similar files

Workflow

Typical usage pattern:

Search for concepts: dev_search { query: "authentication middleware" }
Inspect what you found: dev_patterns { filePath: "src/auth/middleware.ts" }
Analyze dependencies: dev_refs { name: "authMiddleware" }

Performance

Pattern analysis reads from the Antfly index when available (~100ms). Falls back to ts-morph scanning when not (~1-3s).

Migration from dev_explore

If you previously used dev_explore:

dev_explore { action: "similar", query: "file.ts" } → dev_patterns { filePath: "file.ts" }
dev_explore { action: "validate", query: "file.ts" } → dev_patterns { filePath: "file.ts" } (now does both!)
dev_explore { action: "pattern" } → Use dev_search instead
dev_explore { action: "relationships" } → Use dev_refs instead