golang/go

cmd/go: several commands require the build cache but don't use it

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#39,882 opened on Jun 26, 2020

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GoCommandNeedsFixhelp wanted

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Description

Steps to repro:

docker run -i golang:1.15beta1 <<-SCRIPT

        set -ex

        go version
        go env

        mkdir /tmp/foo
        cd /tmp/foo
        go mod init test
        go mod edit -go=1.13

        HOME= GOCACHE= go mod edit -go=1.14

SCRIPT

I think this should succeed. go mod edit -go=X only has to modify a line in go.mod, it shouldn't require the build cache to exist or be writeable. However, that last command fails:

+ go mod edit -go=1.14
build cache is required, but could not be located: GOCACHE is not defined and neither $XDG_CACHE_HOME nor $HOME are defined

I encountered this while writing some tests, which are run in a temporary directory with a near-empty environment (partly to not pollute the user's $HOME and such).

Contributor guide

Research direction
Look at the Go source code for 'go mod edit' (src/cmd/go/internal/modcmd/edit.go) and trace the path where it checks for the build cache. Identify where the cache requirement is enforced unnecessarily and propose a change to skip the cache requirement for commands that don't need it.
Tech stack
go
Domain
backend
Issue type
Bug
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.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Gounderstanding of build cache mechanics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60