Golang Refactoring

Refactoring Workflow — Plan, Stage, Land

• A refactor of any real size is a choreography problem before it is a coding problem.

• This file covers: how to plan the sequence, order the steps so they don't collide, stage them as small human-reviewed PRs, and persist the plan itself — in the code, not just in a conversation that will eventually run out of context — for the intermediate states that are deliberately imperfect and for the ideas that would otherwise be lost.

Table of Contents

• 1. The Planning Gate (mandatory, before any edit)

• 2. Three Interacting Orderings

  • Parallel vs. sequential — decision checklist

• 3. The Git Model

• 4. Parallel vs. Sequential Execution

• 5. The // REFACTOR(step N): ... Marker Convention

• 6. Workflows (ultracode) vs. Human-in-the-Loop

• 7. Human Checkpoints

• Cross-References

1. The Planning Gate (mandatory, before any edit)

Thinking mode: reason as thoroughly as possible here — on Claude Code, use ultrathink to trigger extended thinking explicitly. A wrong ordering call does not surface as an obviously wrong plan — it surfaces later as a broken build or a conflict-riddled merge, once several PRs are already in flight. Getting the sequencing right up front is cheaper than untangling it after the fact.

• Before touching a single line of code, map the blast radius with gopls:

  • find every reference to the symbols you intend to change

  • walk the call hierarchy in both directions

  • check the package's exported API surface for anything an external module might depend on

• Workspace symbol search and gopls codeaction surface the mechanical options available at each site — its day-to-day mechanics (rename, browsing references, call hierarchy) are owned by the samber/cc-skills-golang@golang-gopls skill.

Once the blast radius is mapped, turn it into a refactoring inventory — one row per atomic change, so the whole refactor is visible as a single artifact before any PR exists:

• Risk tiers match the Risk Stratification table in SKILL.md (Low/Medium/High).

• The S/B column marks each row Structural or Behavioral in Kent Beck's sense — a change that alters code shape without altering observable behavior versus a change that alters what the code does.

• Never let one PR carry both letters. A rename and a bug fix touching the same function are two rows, two PRs, two review postures.

• The same one-row-one-concern discipline holds even within a single letter:

  • the move and the loop-optimization rows above are both marked S, but they still earn two separate rows and two sequential PRs

  • a move is verified by gopls plus a green build/test run, while an optimization needs benchmarks (→ See samber/cc-skills-golang@golang-benchmark skill) and a closer read for subtle correctness changes

  • bundling them asks one reviewer to do both jobs at once and denies the move the fast review it earns on its own

  • they also touch the same file, so Ordering (b) below puts them in sequence regardless — never split a move-then-optimize pair across parallel worktrees

• The inventory is not busywork — it is the object every later ordering decision is computed from, and it is what you show the human for sign-off.

This step ends with explicit user sign-off before any code is touched. This is a hard gate, not a suggestion: present the inventory and the staged PR plan derived from it (see below), and wait for approval. A refactor that starts moving code before the human has seen the shape of the whole plan cannot be course-corrected cheaply — by the time a wrong assumption surfaces, several PRs may already be staged on top of it.

2. Three Interacting Orderings

Once the inventory is approved, three independent ordering concerns combine to produce the final sequence. Each answers a different question, and a plan that gets one right while ignoring the others still fails.

• A workspace-wide gopls rename is a barrier.

  • Because it rewrites every reference to a symbol across the whole tree, it necessarily touches files that any other in-flight change might also touch — there is no way to know in advance that it is file-disjoint from everything else in the inventory.

  • Schedule it alone: land every other ready PR before it starts, or hold every other PR until it lands.

  • Do not attempt to run a tree-wide rename concurrently with anything else, even a change that looks unrelated.

Parallel vs. sequential — decision checklist

Run this checklist for every pair of inventory rows you're considering executing at the same time:

If any answer is yes, the two rows are sequential. Only when every answer is no is it safe to run them concurrently.

3. The Git Model

• This is a deliberate, explicit choice for staged refactors — not the only way to refactor, and not necessarily how every Go team runs things day to day.

• Many teams instead land small, independent PRs directly on a fast-moving trunk, treating each one as complete and shippable on its own. That works well when changes are truly independent.

• The model below is chosen here because a staged refactor is not a set of independent changes — it is one coherent transformation broken into reviewable steps, and it needs a place to accumulate before the whole thing is ready to expose to main.

• Reviewability and a human-in-the-loop checkpoint on every step are the tradeoff being made; the cost is an extra integration branch and a final merge step.

The shape:

1. Create a long-lived refactor/<topic> branch off main, and seed it with // REFACTOR(step N): ... markers for the plan itself — see Step 5.

2. For each atomic change in the inventory, in the order established in Step 2, dispatch it to a sub-agent rather than executing it directly in the orchestrating session. The sub-agent, scoped to a fresh worktree, does the work:

   • Enter a fresh, isolated worktree.

   • Create a branch for that one change, based on the current tip of refactor/<topic>.

   • Apply the single change — and nothing else. If the inventory row is turning out larger than ~100–500 lines, that's a signal it's actually two rows: split it before it grows into a diff nobody can review in one sitting.

   • Verify: go build ./... && go vet ./... && go test ./... (add -race or benchstat-backed -bench per the Risk Stratification table in SKILL.md).

     • A staged refactor produces many small PRs in sequence, so weigh the project's actual CI duration against the pace of the refactor: if CI is slow enough that waiting on it between steps would meaningfully stall the sequence — a few minutes is rarely worth front-loading, but a pipeline that takes much longer, repeated across many staged PRs, adds up fast — run the same checks locally first and let CI serve as the final confirmation rather than the primary feedback loop.

     • If CI is already fast, there's no need to duplicate it locally.

   • Open a PR targeting the refactoring branch, not main — ready for review, not a draft, since the whole point of staging is for the human to review and merge it promptly:

     Copy

     gh pr create --base refactor/<topic> --title "..." --body "..."

   • The orchestrating session's own context is the scarcest resource across a long refactor — spending it on every intermediate edit, failed attempt, and tool-output while executing one row leaves less of it for tracking the other rows still ahead and for the ordering decisions in Step 2.

   • Have the sub-agent report back a short result (pass/fail, verification output, PR link) and keep that in the orchestrating session's context — not the sub-agent's full working transcript.

3. A human reviews and merges each of these small PRs into refactor/<topic> at their own pace.

   • Structural PRs should move fast; behavioral PRs get full scrutiny (see Beck ordering above).

   • For any PR that changes code logic rather than just its shape, load samber/cc-skills-golang@golang-security (and golang-safety for internal-correctness risk) alongside this skill before approving it, since a logic change can introduce a vulnerability or a bug that a purely mechanical refactor never could.

4. Only once every row in the inventory has landed on refactor/<topic> — and the TODO-marker sweep in Step 5 is clean — open the final PR merging refactor/<topic> into main, and open this one as a draft: unlike the intermediate PRs, it represents the whole completed transformation and deserves a slower, more deliberate final look before it's marked ready.

Never merge an intermediate PR directly to main. The refactoring branch is the integration point for the entire duration of the refactor; main only ever sees the whole, completed transformation in one final merge. An intermediate PR landing directly on main defeats the purpose of staging — it exposes a deliberately incomplete state (aliases still in place, shims not yet removed) to every other branch built off main in the meantime.

4. Parallel vs. Sequential Execution

• When multiple inventory rows are ready — their dependency-order prerequisites have landed, and the checklist in Step 2 says "no" on every question — launch them concurrently, one sub-agent per row, each in its own worktree, its own branch off the current tip of refactor/<topic>, and its own PR.

  • This is where a large refactor's wall-clock time actually shrinks: three file-disjoint structural changes reviewed at once cost the same calendar time as one — and the orchestrating session still only keeps three short results, not three full working transcripts.

• When rows overlap — same file, same symbol, or a dependency relationship — run them one at a time: land the first on refactor/<topic> before branching the second off the new tip.

  • Trying to parallelize overlapping rows just moves the conflict from merge time to rebase time, and a human reviewer now has to untangle a diff that mixes two unrelated changes.

• The workspace-wide-rename-is-a-barrier rule from Step 2 applies here without exception: never schedule a tree-wide rename alongside any other in-flight worktree, regardless of how unrelated the files look on paper.

5. The // REFACTOR(step N): ... Marker Convention

The marker has two jobs, and the first matters more than it looks.

• Job 1 — surviving context loss. A multi-step refactor eats context fast:

  • it can span many sessions, and each new session (or a different agent picking up the work) starts with a fresh, limited context window that has no memory of the planning conversation

  • a conversation is a bad place to keep a plan safe; the codebase, committed to the refactoring branch, is not

  • so right when you create refactor/<topic> (Step 3), before any change lands, seed it liberally with markers at every point the inventory identifies future work, an idea worth not losing, or a decision that won't be obvious from a later diff — not only at points of deliberate imperfection

  • a marker survives exactly the kind of context loss a plan that only ever existed in conversation does not

  • Skip this for a small refactoring. A single-PR change, or the simple mechanical sweep in Section 6, doesn't have a plan large enough to be worth losing — seeding markers there is noise, not insurance. Reserve liberal marker-seeding for staged, multi-PR refactors, where the plan is genuinely too large to trust to any one session's memory.

• Job 2 — flagging deliberate imperfection. A staged refactor will, by design, pass through intermediate states that are imperfect on purpose — a type alias kept around so callers can migrate one PR at a time, a shim left in place until a later step removes it, an old code path still reachable until its last caller is gone.

  • This is fine and expected. The risk isn't the imperfection — it's forgetting about it once the PR that introduced it has merged and attention has moved on.

Mark every such spot — a plan note or a deliberate imperfection — with a comment that names the step and the reason:

// REFACTOR(step 3): remove this alias once all callers in pkg/foo migrate to bar.New (see refactor/<topic>)

• Each marker earns its place twice over: it tells a reviewer looking at this PR that the current state is intentional, not an oversight, and it hands context forward — to whichever later step, later PR, or entirely different agent session eventually acts on it — about exactly what is pending and why.

• Without it, a shim that "temporarily" bridges old and new callers has a way of becoming permanent simply because nothing points back at it, and an idea from the planning gate has a way of vanishing the moment the session that had it ends.

The final sweep, run just before opening the PR that merges refactor/<topic> into main, must find zero remaining markers:

grep -rn "REFACTOR(" .

Diagnose: grep -rn "REFACTOR(" . — must return no results before the final merge to main; any hit means a planned step never landed, and the refactor is not actually done even though every individual PR merged cleanly.

6. Workflows (ultracode) vs. Human-in-the-Loop

• Claude Code's Workflow feature (ultracode) orchestrates multiple sub-agents across multiple stages automatically, with no human checkpoint between them.

• That is exactly the wrong shape for a staged refactor, whose entire value proposition is a human reviewing and merging each small PR before the next step is allowed to build on it.

• Running a multi-step refactor through Workflows collapses the review checkpoints this whole document exists to preserve — by the time a human looks at anything, several dependent stages may have already executed on top of a decision nobody signed off on.

• Reach for Workflows/ultracode only when the refactor is genuinely a single mechanical sweep in one pass — one gofmt -r rule, one eg template, or one modernize-style fixer applied tree-wide, verified green by the build/vet/test loop, with nothing else in the inventory depending on it.

  • That case has no staging problem to begin with: there is exactly one step, and it either lands or it doesn't.

• For anything requiring progressive review across multiple merges — which is the common case for a real refactor — use the worktree + PR + human-review flow in Steps 3 and 4 instead, and do not reach for Workflows.

7. Human Checkpoints

The same triggers as SKILL.md's "Pause for human sign-off before" list apply here — cross-package moves, exported-API changes, deletions, new major versions, untested code — and they're not one-time: get sign-off on each one again if it comes up mid-refactor, even after the planning gate has already been cleared once. For untested code specifically, that means sign-off on the characterization-test baseline (see safety-net.md) before refactoring it, not after.

Structural-only PRs are reversible and low-risk by construction (Beck's separation is the whole reason they're safe to move fast on) and can be fast-reviewed. Behavioral PRs — anything that changes what the code does, not just how it's shaped — get full scrutiny every time, regardless of how small the diff looks.

Cross-References

• catalog.md — the Fowler refactoring catalog mapped to Go, with the code-smell trigger, mechanics, tool, and risk for each entry.

• go-tooling.md — gopls code actions, CLI invocation, gofmt -r, eg, gopatch, and go/analysis fixers referenced throughout the inventory examples above.

• safety-net.md — the coverage-adaptive strategy and characterization-testing recipes referenced in the Human Checkpoints section.

• structural.md — import-cycle breaking, package-boundary design, and the type-alias gradual-repair mechanism referenced in the inventory example above.

• → See samber/cc-skills-golang@golang-security skill (and golang-safety) for reviewing any PR that changes code logic, per Step 3 above.