feat(auto-format): run configured formatters on files edited by write…

[AniketR10]

Description

runs a configured formatter on files after write_file or string_replace edits them. config is under nanocoder.autoFormat in agents.config.json. off by default. failures just show a chat message and don't block anything. closes #1009

Type of Change

• New feature

Changeset

• Added a changeset (pnpm changeset) describing this change for the changelog

Testing

Automated Tests

• New features include passing tests in .spec.ts/tsx files
• All existing tests pass (pnpm test:all completes successfully)
• Tests cover both success and error scenarios

Manual Testing

• Tested with Ollama
• Tested with OpenRouter
• Tested with OpenAI-compatible API
• Tested MCP integration (if applicable)

Checklist

• If this was for an open issue, I was assigned to it
• Code follows project style guidelines
• Self-review completed
• Documentation updated (if needed)
• No breaking changes (or clearly documented)
• Appropriate logging added using structured logging (see CONTRIBUTING.md)

[AniketR10]

@will-lamerton @akramcodez @Avtrkrb please review

[Copilot]

🟡 Changes recommended

There are verified correctness/documentation issues around {file} quoting (notably on Windows/cmd.exe) and config validation/doc mismatches that should be addressed before merge.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds an opt-in “auto-format after edits” hook to the conversation loop, driven by a new nanocoder.autoFormat config section, so files modified by write_file / string_replace can be reformatted automatically without involving the model.

Changes:

• Introduces AutoFormatConfig / AutoFormatFormatterConfig and loads/validates nanocoder.autoFormat from agents.config.json.
• Wires processAssistantResponse to run per-turn formatting after successful edit tools and surface failures only as user-visible chat messages.
• Adds AVA coverage for both the core formatter runner and the conversation-loop wiring, plus docs + changeset.

File summaries

File	Description
source/types/config.ts	Adds config types for nanocoder.autoFormat (enabled, formatters, timeout).
source/hooks/chat-handler/conversation/conversation-loop.tsx	Invokes runAutoFormat() after tool execution and reports failures via InfoMessage.
source/hooks/chat-handler/conversation/auto-format.ts	Implements per-file formatter matching, {file} substitution, and command execution with timeout.
source/hooks/chat-handler/conversation/auto-format.spec.ts	Adds unit/integration tests for the auto-format runner and conversation-loop wiring.
source/config/index.ts	Adds config loading + validation for nanocoder.autoFormat with safe defaults.
source/config/index.spec.ts	Adds config resolution tests for auto-format defaults, parsing, and malformed entries.
docs/configuration/index.md	Documents nanocoder.autoFormat options and examples.
.changeset/auto-format-on-save.md	Adds changelog entry for the new auto-format feature.

Review details

Suppressed comments (2)

source/hooks/chat-handler/conversation/auto-format.ts:98

• The doc comment claims that a "no match" is reported as a failure outcome, but the implementation silently skips files with no matching formatter (returns no outcome at all). This is misleading for future maintainers and for callers that might expect an outcome per edited file.

 * Run configured formatters against every file successfully touched by an
 * edit tool (`write_file`, `string_replace`) this turn. Silent on success;
 * every failure (no match, non-zero exit, timeout, missing binary) is
 * captured as an outcome instead of thrown, so a misconfigured or missing
 * formatter never interrupts the conversation.

source/hooks/chat-handler/conversation/auto-format.ts:121

• {file} is substituted using POSIX single-quote escaping (shellQuote). On Windows this code runs commands via cmd.exe (see pickShell()), where single quotes are not quoting, so paths with spaces/special characters can break formatting (and quoting is inconsistent with the shell actually used). Quote the file path appropriately for cmd.exe.

		const absolutePath = isAbsolute(path) ? path : resolve(cwd, path);
		const command = formatter.command.replaceAll(
			'{file}',
			shellQuote(absolutePath),
		);

• Files reviewed: 8/8 changed files
• Comments generated: 4
• Review effort level: Lite

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