Refactor Go Code using Comby

This guide explains how to use Comby to refactor Go code in a batch change.

To refactor Go code using Comby in a batch change, use Sourcegraph's structural search and Comby to rewrite Go statements.

From:

GO
fmt.Sprintf("%d", number)

To:

GO
strconv.Itoa(number)

The statements are semantically equivalent, but the latter is more precise.

Since the replacements could require importing the strconv package, it uses goimports to update the list of imported packages in all *.go files.

Prerequisites

Before you start, it's better to read the following docs:

• Batch Changes Quickstart
• How to create and run a Batch Spec?

Create the batch spec

Save the following batch spec YAML as sprintf-to-itoa.batch.yaml:

YAML
name: sprintf-to-itoa
description: |
  This batch change uses [Comby](https://comby.dev) to replace `fmt.Sprintf` calls
  in Go code with the equivalent but clearer `strconv.Iota` call.
 
on:
  - repositoriesMatchingQuery: lang:go fmt.Sprintf("%d", :[v]) patterntype:structural
 
steps:
  - run: comby -in-place 'fmt.Sprintf("%d", :[v])' 'strconv.Itoa(:[v])' .go -matcher .go -exclude-dir .,vendor
    container: comby/comby
  - run: goimports -w $(find . -type f -name '*.go' -not -path "./vendor/*")
    container: unibeautify/goimports
 
changesetTemplate:
  title: Replace fmt.Sprintf with equivalent strconv.Itoa
  body: This batch change replaces `fmt.Sprintf` with `strconv.Itoa`
  branch: batch-changes/sprintf-to-itoa
  commit:
    message: Replacing fmt.Sprintf with strconv.Iota
  published: false

Create the batch change

• In your terminal, run the following command:

SHELL
src batch preview -f sprintf-to-itoa.batch.yaml

• Wait for it to run and compute the changes for each repository
• Open the preview URL that the command printed out
• Examine the preview. Confirm that the changesets are the ones you intended to track. If not, edit the batch spec and then re-run the command above
• Click the Apply button to create the batch change
• Feel free to then publish the changesets (i.e., create pull requests and merge requests) by modifying the published attribute in the batch spec and re-running the src batch preview command