snap build fails if go must download the version
Metadata
Current evaluation
Go plugin validation misreads a toolchain-download message from stderr as the compiler version, so the first clean snapcraft pack fails while retries succeed; it remains unfixed and untriaged.
Suggested action: needs triage
Reason: The current validator still returns proc.stderr whenever non-empty, and Go validation rejects any result not starting with "go version", confirming the reported root cause. The authd command, part YAML, first-run failure, and retry workaround make it reproducible, while current unit fixtures cover only stdout; no fix or maintainer triage is present and the only comment requests assignment.
Evaluated by: mr-cal-bot
Impact:
48
Quick Win:
31
Complexity:
30
Confidence:
96
Actionability:
92
Issue body
### Bug Description
I see `snapcraft pack` fail with:
```
Environment validation failed for part 'semver': invalid go compiler version 'go: downloading go1.25.6 (linux/amd64)'.
Failed to run snapcraft in instance
```
It works when I execute `snapcraft pack` again. I assume that's because the required Go version was then already downloaded on the instance.
I took a quick look at the code where this error originates from. [This](https://github.com/canonical/craft-parts//blob/71291d50ec95aed813215e89463866dd09aaaa5e/craft_parts/plugins/go_plugin.py#L66-L71) is the call to `go version` which calls `subprocess.run` and [returns the stderr](https://github.com/canonical/craft-parts//blob/71291d50ec95aed813215e89463866dd09aaaa5e/craft_parts/plugins/validator.py#L145-L152) it it's non-empty, which it then assumes is the go version. It should use the output on stdout instead.
### To Reproduce
I encounter this when trying to build the authd snaps:
```bash
git clone https://github.com/canonical/authd
cd authd
# Prepare snapcraft.yaml
./scripts/prepare-broker-variant-files
# Build the snap
snapcraft pack
```
### part yaml
```yaml
semver:
source: authd-oidc-brokers/tools
source-type: local
plugin: go
override-build: |
go mod download all
go mod vendor
go build -o ${GOBIN}/semver semver/semver.go
```
### Relevant log output
I assume the above is enough to understand the issue. Let me know if you do need logs.
Evaluation history
| Date | Model | Scores | Action | Summary |
|---|---|---|---|---|
| stealth/space-bunny-alpha |
Impact:
48
Quick Win:
31
Complexity:
30
Confidence:
96
Actionability:
92
|
needs triage | Go plugin validation misreads a toolchain-download message from stderr as the compiler version, so the first clean snapcraft pack fails while retries succeed; it remains unfixed and untriaged. | |
| stealth/space-bunny-alpha |
Impact:
58
Quick Win:
33
Complexity:
30
Confidence:
84
Actionability:
82
|
needs triage | snapcraft pack fails for the go plugin when `go version` must first download a toolchain: validator._execute returns stderr when non-empty, so "go: downloading go1.25.6" is mistaken for the version. Unfixed; contributor asked to be assigned. | |
| qwen/qwen3.6-35b-a3b |
Impact:
60
Quick Win:
38
Complexity:
20
Confidence:
85
Actionability:
80
|
keep open | Go plugin environment validation fails when Go downloads a version, because stderr download message is returned instead of stdout version output | |
| qwen/qwen3.8-27b |
Impact:
55
Quick Win:
41
Staleness:
15
Complexity:
25
Confidence:
80
Support Request:
5
|
keep open | Go plugin env validation in craft-parts fails when `go version` triggers a toolchain auto-download, because validator._execute returns stderr ('go: downloading go1.25.6...') instead of stdout. Bug confirmed present in current code; a contributor requested assignment 8 days ago. | |
| qwen/qwen3.8-27b |
Impact:
45
Quick Win:
29
Staleness:
20
Complexity:
35
Confidence:
85
Support Request:
5
|
needs triage | Go plugin environment validation fails on first build when go auto-downloads a toolchain, because validator._execute returns stderr ('go: downloading go1.25.6...') instead of stdout. Bug confirmed still present in current code; contributor volunteered 8 days ago, no labels or maintainer response yet. | |
| qwen/qwen3.8-27b |
Impact:
45
Quick Win:
29
Staleness:
25
Complexity:
35
Confidence:
85
Support Request:
5
|
needs triage | snapcraft pack fails on first run of a go part when go auto-downloads a toolchain: the validator reads stderr of `go version` and misreads the 'go: downloading...' message as the version. Bug still present in craft-parts; a contributor asked to be assigned 8 days ago. | |
| qwen/qwen3.6-35b-a3b |
Staleness:
70
Complexity:
10
Confidence:
90
Support Request:
0
|
needs triage | Go plugin incorrectly reads stderr instead of stdout when checking Go version, causing snapcraft pack to fail during version downloads. Untriaged and awaiting maintainer review. | |
| qwen3.6-35b-a3b-mtp-q6 |
Staleness:
45
Complexity:
15
Confidence:
85
Support Request:
0
|
needs triage | Bug in craft-parts Go plugin where go version reads stderr instead of stdout, causing failures when Go needs to download a version. A contributor recently volunteered to fix it. |
Update history
| Date | Change |
|---|---|
| updated |
Related work
-
Duplicate Of:
rockcraft#902
(confidence 98%)
Open downstream report of the same toolchain-download stderr validation failure that explicitly identifies craft-parts#1447 as the duplicate and root-cause issue.
Related issues
| Issue | Project | State | Summary | Similarity |
|---|---|---|---|---|
| #902 Go plugin environment validation fails if toolchain downloads a new version | rockcraft | open | Go plugin env validation fails when `go version` triggers toolchain auto-download; stderr download message is parsed as the version. Root cause is in craft-parts validator; duplicate craft-parts#1447 is open. |