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Support Go 1.26 and later with Swiss maps always enabled #19088

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Merged
mattlord merged 1 commit into from
Jan 13, 2026
Merged

Support Go 1.26 and later with Swiss maps always enabled #19088

mattlord merged 1 commit into from
Jan 13, 2026

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@stefanb
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@stefanb stefanb commented Dec 25, 2025 •
edited by mattlord
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Description

Adjusts Go build flags for ensuring Swiss maps are available to not trigger false positive compile-time errors with Go 1.26 and later.
In Go 1.26 and later Swiss maps are always enabled and cannot be disabled anymore (as was the case in Go 1.24-1.25) and there is no more GOEXPERIMENT=noswissmap flag. See:

Related Issue(s)

Fixes #19087

Checklist

  • "Backport to:" labels have been added if this change should be back-ported to release branches
  • If this change is to be back-ported to previous releases, a justification is included in the PR description
  • Tests were added or are not required
  • Did the new or modified tests pass consistently locally and on CI?
  • Documentation was added or is not required

Deployment Notes

N/A

AI Disclosure

No AI was used for preparing this patch.

@stefanb
Support Go 1.26 and later with Swiss maps enabled by default
1e131ea 
In Go 1.26 and later Swiss maps are enabled by default and there is no more GOEXPERIMENT=noswissmap nor GOEXPERIMENT=swissmap flag either. See:
* golang/go@2ae059c
* golang/go#54766

Signed-off-by: Štefan Baebler <[email protected]>
@github-actions github-actions bot added this to the v24.0.0 milestone Dec 25, 2025
@vitess-bot vitess-bot bot added NeedsWebsiteDocsUpdate What it says NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsIssue A linked issue is missing for this Pull Request NeedsBackportReason If backport labels have been applied to a PR, a justification is required labels Dec 25, 2025
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vitess-bot bot commented Dec 25, 2025

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@stefanb stefanb mentioned this pull request Dec 25, 2025
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dbussink
dbussink reviewed Dec 26, 2025
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go/hack/ensure_swiss_map.go
@@ -1,4 +1,4 @@
//go:build !goexperiment.swissmap
//go:build !goexperiment.swissmap && !go1.26
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@dbussink dbussink Dec 26, 2025

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We should flip this flag to goexperiment.swissmap .noswissmap instead of !goexperiment.swissmap which would work also still for 1.26 if the flag is entirely gone?

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@stefanb stefanb Dec 29, 2025

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Yes, that would be much cleaner, if goexperiment.noswissmap build constraint existed.

GOEXPERIMENT=noswissmap environment setting existed in Go 1.24 and 1.25 to disable swiss maps and was negated mapped to goexperiment.swissmap build constraint. Hence the confusion.

In go 1.26 GOEXPERIMENT=noswissmap is not supported anymore and there is no way to set goexperiment.swissmap build constraint either, so the only option is to check for go1.26 build constraint.

@stefanb stefanb changed the title Support Go 1.26 and later with Swiss maps enabled by default Support Go 1.26 and later with Swiss maps always enabled Dec 28, 2025
stefanb added a commit to Homebrew/homebrew-core that referenced this pull request Jan 5, 2026
@stefanb
vitess: add go1.26 build patch
fb7426a 
PR ref:
* Upstream vitessio/vitess#19088
* #258912
@stefanb stefanb mentioned this pull request Jan 5, 2026
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@mattlord mattlord added Component: Build/CI Type: CI/Build and removed NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsWebsiteDocsUpdate What it says NeedsIssue A linked issue is missing for this Pull Request NeedsBackportReason If backport labels have been applied to a PR, a justification is required labels Jan 6, 2026
mattlord
mattlord approved these changes Jan 6, 2026
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Thanks, @stefanb !

@mattlord mattlord merged commit 28105fd into vitessio:main Jan 13, 2026
116 of 123 checks passed
@stefanb stefanb deleted the Go-1.26-support branch January 13, 2026 20:45
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@mattlord mattlord mattlord approved these changes

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Build fails with Go 1.26 rc1

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