Refactoring a legacy module in Fiber with Atlas ensures you can restructure code without changing its behavior or breaking callers, leveraging Atlas's deep code understanding and your existing `go test (app.Test)` and `gofmt` toolchain. Atlas uses the `lsp` tool to map public surfaces and `findReferences` to enumerate every callsite, providing a comprehensive view before any changes are made.
How Atlas Maps Fiber Module Surfaces and Callers
In 2026, Atlas helps Fiber developers understand their module's public surface and callers by leveraging the `lsp` tool's `documentSymbol` and `findReferences` operations. This crucial first step ensures that every interaction with the legacy module is identified before any refactoring begins, preventing silent breakage.
Atlas begins a Fiber module refactor by building a comprehensive understanding of its public interface. Using the `lsp` tool, Atlas performs a `documentSymbol` operation to identify all exported symbols within your Fiber application, including `app.Group` routes, `fiber.Ctx` handlers, and registered middleware. Following this, Atlas executes `findReferences` on each identified symbol. This process enumerates every single callsite across your codebase, providing a complete map of where the legacy module is being used. This detailed mapping is fundamental to the refactoring workflow, as it allows Atlas to track all potential impacts and ensure that no caller is inadvertently broken during the restructuring process.
Pinning Fiber Module Behavior with `go test (app.Test)`
Before any structural changes are applied to a Fiber module, Atlas ensures behavioral integrity by pinning the existing behavior. This involves running your `go test (app.Test)` suite with the `bash` tool to establish a green baseline, a critical step in 2026 for safe refactoring.
A core principle of safe refactoring is to first establish a reliable behavioral baseline. Atlas achieves this by using its `bash` tool to execute your Fiber application's test suite. Specifically, Atlas runs the command `go test (app.Test) ./...` to capture the current, expected behavior of the module. This initial 'green' baseline serves as a contract: any subsequent changes must not alter this established behavior. Atlas records the output of these tests, providing a clear reference point. This step is particularly important for Fiber handlers, where `app.Test()` is used to verify functionality, ensuring that even complex request/response flows remain consistent throughout the refactoring process.
Applying Structural Changes to Fiber Code with `apply_patch`
Atlas applies structural changes to your Fiber module using the `apply_patch` tool, which offers a robust safety mechanism. Each hunk is anchored on context lines and `old_lines`, and if a file has drifted, `apply_patch` will fail with 'Failed to find context', preventing unintended modifications in 2026.
Once the public surface is mapped and the behavioral baseline is pinned, Atlas proceeds with the actual restructuring of the Fiber module. This is done using the `apply_patch` tool, which is designed for precise and safe code modifications. Unlike blind line-based edits, `apply_patch` anchors each hunk of changes on specific context lines and the exact `old_lines` it expects to find. This mechanism provides a crucial safety net: if the target Fiber file has been modified or 'drifted' since Atlas last read it, `apply_patch` will refuse to apply the change, reporting 'Failed to find context'. This prevents accidental overwrites or corruptions. The workflow dictates that changes are applied iteratively, with `go test (app.Test)` being re-run after each hunk lands, not just once at the end, to continuously verify behavior.
Ensuring Fiber Code Quality and Tracking Refactor Progress
Atlas ensures high code quality in your Fiber refactor by integrating `gofmt` and providing a unified diff for every edit. It also helps track progress with the `todowrite` tool, preventing partially migrated modules from being mistaken for finished ones in 2026.
Maintaining code quality and tracking progress are vital during a Fiber module refactor. Atlas integrates direct with `gofmt`, prompting you to approve the diff and then running `gofmt` on touched files to ensure consistent formatting across your codebase. Every file edit proposed by Atlas is presented as a unified diff, allowing for explicit approval before any changes are written to disk. Furthermore, Atlas leverages its `git` integration to snapshot file changes as patches, enabling easy diffing and rollback if needed. For complex refactors, the `todowrite` tool is used to track remaining callsites that still need migration, ensuring that a partially refactored Fiber module is never mistakenly considered complete. Atlas also helps manage `fasthttp`'s buffer reuse in Fiber by asking to copy any `fiber.Ctx` value retained past the handler.
Step by step
- 01Run Atlas in your Fiber module, ensuring your `go.mod` requires `github.com/gofiber/fiber/v3`.
- 02Map the Fiber module's public surface and callers using `atlas lsp documentSymbol` and `atlas lsp findReferences` for each exported symbol.
- 03Pin existing behavior by running your test suite: `atlas bash "go test (app.Test) ./..."` to record a green baseline.
- 04Restructure the Fiber module iteratively with `atlas apply_patch`, re-running `atlas bash "go test (app.Test) ./..."` after each hunk lands.
- 05Track remaining callsites for migration using `atlas todowrite "Migrate callsite for [symbol] in [file]"`.
- 06Approve the unified diff for changes, then ensure consistent formatting by running `atlas bash "gofmt -w ."` on touched files.
- 07Commit your refactored Fiber module changes with `atlas git commit -m "Refactor Fiber module [name]"`.
Frequently asked questions
- How does Atlas ensure my Fiber refactor doesn't break existing callers?
- Atlas uses the `lsp` tool's `findReferences` operation to enumerate every callsite of a Fiber module's public symbols before any changes, ensuring all callers are accounted for and preventing silent breakage.
- Can Atlas help with `fasthttp` buffer lifetime issues in Fiber during refactoring?
- Yes, Atlas is aware of `fasthttp`'s buffer reuse in Fiber and can be asked to copy any `fiber.Ctx` value you retain past the handler, preventing unexpected data corruption during refactoring.
- How does Atlas integrate with my existing Fiber testing workflow?
- Atlas integrates directly with your existing `go test (app.Test)` workflow, using its `bash` tool to run tests and record a green baseline, then re-running them after each change to continuously verify behavior.
- What happens if Atlas tries to apply a change to a Fiber file that I've already modified?
- Atlas's `apply_patch` tool anchors on context lines and `old_lines`. If a Fiber file has drifted from the expected state, `apply_patch` will fail with `Failed to find context`, preventing unintended overwrites.
- Does Atlas automatically format my Fiber code with `gofmt`?
- After applying changes, Atlas prompts you to approve the diff and can then run `gofmt` on the touched Fiber files via a permission prompt, ensuring consistent code style across your project.
- How does Atlas help track progress on a large Fiber module refactor?
- Atlas uses the `todowrite` tool to track remaining callsites that need migration, ensuring that a partially refactored Fiber module is not mistakenly considered complete and providing clear progress visibility.
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