golang/go

x/tools/gopls: when editing Go files in GOMODCACHE, offer to clone module and add replace directive

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#77,212 opened on Jan 16, 2026

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FeatureRequestToolsgoplshelp wanted

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Description

Being able to quickly edit the standard library (e.g. by inserting a print statement) is extremely useful during debugging. However, editing source files from dependencies within the module cache is not as convenient. Gopls could detect an attempt to modify such a file and offer to clone the module, add a replace directive to the main module, and move the cursor to the corresponding position in the cloned file, which can then be freely edited. The replace directive could be flagged with a // FIXME: debugging comment, with a code action to revert it.

(Credit to @prattmic for the idea.)

Contributor guide

Research direction
Investigate how gopls detects file changes and implement logic to clone a module from GOMODCACHE, add a replace directive, and open the cloned file at the cursor position. Use the existing go.mod parsing and editing capabilities in gopls.
Tech stack
go
Domain
backendtooling
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Gogopls
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60