Add CLI command typo detection (#34836)

[MitchLewis930]

PR_040

[greptile-apps]

Greptile Overview

Greptile Summary

This PR adds CLI command typo detection using Levenshtein distance to help users who mistype Next.js commands.

Key changes:

• Implemented detectTypo() function using Levenshtein distance algorithm with a threshold of 2 edit operations
• Exported the commands object from next.ts to make valid commands available for typo checking
• Added typo detection in getProjectDir() error handler to catch misspelled commands and suggest corrections
• Added comprehensive test coverage for common typos (buidl → build, starr → start, etc.)

How it works:
When a user types an invalid command like next buidl, the CLI treats it as a directory argument to the default dev command. When getProjectDir() fails to resolve the path, it checks if the string matches any command names within 2 edit operations and suggests the closest match.

Confidence Score: 4/5

• Safe to merge with minor optimization opportunity
• Implementation is sound with good test coverage. The Levenshtein algorithm is correct and the integration works as intended. Minor style improvement possible (unused threshold parameter), but no functional issues found.
• No files require special attention

Important Files Changed

Filename	Overview
packages/next/lib/detect-typo.ts	New file implementing Levenshtein distance algorithm for typo detection with default threshold of 2
packages/next/lib/get-project-dir.ts	Added typo detection logic in ENOENT error handler to suggest correct commands before showing directory error

Sequence Diagram

sequenceDiagram
    participant User
    participant CLI as next.ts (CLI)
    participant Command as next-dev/build/etc
    participant GetDir as getProjectDir()
    participant Detector as detectTypo()
    
    User->>CLI: next buidl
    CLI->>CLI: Check if "buidl" in commands
    Note over CLI: foundCommand = false
    CLI->>CLI: Set command = "dev" (default)
    CLI->>CLI: Set forwardedArgs = ["buidl"]
    CLI->>Command: Execute dev(["buidl"])
    Command->>GetDir: getProjectDir("buidl")
    GetDir->>GetDir: Try fs.realpathSync("buidl")
    GetDir->>GetDir: Error: ENOENT (no such dir)
    GetDir->>Detector: detectTypo("buidl", ["build", "start", ...])
    Detector->>Detector: Calculate Levenshtein distance
    Detector->>Detector: Filter distance <= 2 and > 0
    Detector->>Detector: Sort by distance
    Detector-->>GetDir: Return "build"
    GetDir->>GetDir: Log.error("Did you mean 'next build'?")
    GetDir->>GetDir: process.exit(1)
    GetDir-->>User: Error message displayed

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[greptile-apps]

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[greptile-apps]

threshold parameter unused - could optimize by early-exiting when distance exceeds threshold

Prompt To Fix With AI

This is a comment left during a code review.
Path: packages/next/lib/detect-typo.ts
Line: 2:2

Comment:
`threshold` parameter unused - could optimize by early-exiting when distance exceeds threshold

How can I resolve this? If you propose a fix, please make it concise.