feat: Refactor localization to YAML catalogs with runtime language overrides

[Copilot]

• Inspect failing lint workflow run and fetch failing job logs
• Identify exact lint error and impacted file/line
• Reproduce lint failure locally using golangci-lint v2.7.2
• Apply minimal code fix for lint error (interface{} -> any)
• Re-run local lint to confirm pass (0 issues)
• Run targeted tests for changed package (go test ./server/core/config/...)
• Run formatting check (make check-fmt)
• Run validation checks
• Address validation feedback: improve decodeYAML doc clarity for yaml.v3 merge-key panic handling
• Address validation feedback: strengthen Spanish plan rendering test with plan-specific assertion and plan-success result
• Re-run lint/tests locally (golangci-lint run, go test ./server/core/config/... ./server/events/...)
• Re-run validation checks and report results

[Copilot]

Pull request overview

This PR refactors Atlantis comment localization from hardcoded strings to embedded YAML catalogs, and adds support for operator-provided runtime language overrides via a custom YAML catalog file (without rebuilding the binary).

Changes:

• Added server/i18n package with embedded YAML catalogs (en, es) plus merge/override behavior for custom catalogs.
• Wired language selection and custom catalog path through CLI flags/config into events.MarkdownRenderer.
• Added Spanish template overrides under server/events/templates/i18n/es/ and expanded unit tests + docs for the new config options.

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
server/user_config.go	Adds language and language-config-file to server user config.
server/server.go	Wires i18n.TranslatorConfig into markdown renderer construction.
server/i18n/locales/en.yaml	Adds built-in English YAML catalog.
server/i18n/locales/es.yaml	Adds built-in Spanish YAML catalog.
server/i18n/i18n.go	Implements catalog parsing, merging, language normalization/validation, and translator.
server/i18n/i18n_test.go	Adds unit tests for normalization, validation, built-in loading, and custom override behavior.
server/events/templates/i18n/es/wrapped_err.tmpl	Spanish override for wrapped error rendering.
server/events/templates/i18n/es/unwrapped_err.tmpl	Spanish override for unwrapped error rendering.
server/events/templates/i18n/es/single_project_plan_unsuccessful.tmpl	Spanish override for single-project unsuccessful plan template.
server/events/templates/i18n/es/single_project_plan_success.tmpl	Spanish override for single-project successful plan template (with instructions).
server/events/templates/i18n/es/single_project_apply.tmpl	Spanish override for single-project apply template.
server/events/templates/i18n/es/multi_project_plan.tmpl	Spanish override for multi-project plan template.
server/events/templates/i18n/es/multi_project_plan_footer.tmpl	Spanish override for plan footer summary/instructions.
server/events/templates/i18n/es/multi_project_header.tmpl	Spanish override for multi-project header template.
server/events/templates/i18n/es/multi_project_apply.tmpl	Spanish override for multi-project apply template.
server/events/templates/i18n/es/multi_project_apply_footer.tmpl	Spanish override for apply footer summary.
server/events/templates/i18n/es/log.tmpl	Spanish override for verbose log template.
server/events/templates/i18n/es/failure.tmpl	Spanish override for failure template.
server/events/markdown_renderer.go	Loads localized template sets; uses translator for command/vcs labels; introduces config-based localization.
server/events/markdown_renderer_test.go	Adds tests for Spanish localization and custom catalog overrides.
runatlantis.io/docs/server-configuration.md	Documents --language and --language-config-file with schema and behavior.
cmd/server.go	Adds flags/env wiring, defaults, and validation for language + custom catalog.
cmd/server_test.go	Adds validation coverage for language selection and custom catalog errors.

Comments suppressed due to low confidence (1)

server/events/markdown_renderer.go:281

• policyCheckResultsWrapped/policyCheckResultsUnwrapped templates gate some content behind if eq .Command "Policy Check". With localization/custom command titles, common.Command is no longer guaranteed to be "Policy Check", so those sections will be skipped for policy_check results. Consider passing a stable (non-localized) command title into the policyCheckResultsData used for these templates so the condition remains correct regardless of localization.

		} else if result.PolicyCheckResults != nil && matchesCommandTitle(common.Command, policyCheckCommandTitle, m.translator) {
			policyCheckResults := policyCheckResultsData{
				PreConftestOutput:     result.PolicyCheckResults.PreConftestOutput,
				PostConftestOutput:    result.PolicyCheckResults.PostConftestOutput,
				PolicyCheckResults:    *result.PolicyCheckResults,

[jamengual]

Code Review

Reviewed +996/-51 across 30 files. Two distinct changes bundled: localization framework + unrelated yaml.v3 merge-key panic fix.

Strengths

• Stable identifier fix. Decoupling common.Command (display) from common.CommandName (routing key) fixes real bug where translated titles broke template selection. TestRenderUsesStableCommandIdentifierWhenTitlesCollide validates this.
• Test coverage solid: Spanish render, custom override, colliding titles, policy check rendering, YAML panic regression.
• AGENTS.md updated with lesson learned — self-documenting.
• YAML panic fix: recover() wrapper minimal, scoped to user YAML decode. Fuzz seed committed.

Issues

HIGH — Bundled unrelated changes. PR mixes localization feature (~950 lines) with yaml.v3 merge-key panic fix (~70 lines + fuzz). Should be 2 PRs. Reviewers and git bisect suffer. PR body reads as a lint-fix task list; doesn't describe feature scope.

MEDIUM — Variadic config is non-idiomatic.

func NewMarkdownRenderer(..., localizationConfigs ...i18n.TranslatorConfig) *MarkdownRenderer

Variadic for an optional single value is an anti-pattern; only first element used, extras silently ignored. Prefer *i18n.TranslatorConfig (nil = default), a functional-option pattern, or a separate constructor.

MEDIUM — MustNewTranslator misleading + silently swallows errors.

func MustNewTranslator(config TranslatorConfig) *Translator {
    translator, err := NewTranslator(config)
    if err == nil { return translator }
    translator, _ = NewTranslator(TranslatorConfig{LanguageCode: DefaultLanguage})
    if translator != nil { return translator }
    return &Translator{...}
}

Name suggests panic on failure; it never panics. Rename NewTranslatorOrDefault. Triple fallback masks config errors with no log — since cmd/server.go validates upfront, this is "unreachable", but if reached operator sees no signal. Add logger.Warn on fallback.

MEDIUM — Custom catalog YAML not protected from same panic.
parseCatalog in server/i18n/i18n.go calls yaml.Unmarshal directly. Same merge-key panic class affects operator-supplied --language-config-file. Recommend route parseCatalog through a recover() wrapper (or reuse decodeYAML-style helper) for symmetry. Otherwise a malformed custom catalog crashes startup.

LOW — decodeYAML error strips stack.

retErr = fmt.Errorf("yaml: unexpected error while parsing: %v", r)

For an upstream library bug, debugging benefits from stack. Consider attaching debug.Stack() at DEBUG log level before converting to error.

LOW — Embed glob fragility.

//go:embed templates/*.tmpl templates/i18n/*/*.tmpl

New locale directory with typo (e.g. zh-CN) silently falls back to English. Consider asserting locale subdirs match supportedLanguages at init.

LOW — Spanish strings need native review.

• "Pull Request" → "Solicitud de extracción": technically correct but Spanish devs typically leave untranslated.
• "Policy Check" → "Verificar políticas": verb form inconsistent with noun titles ("Aplicar", "Planificar").

Security / Performance

No security concerns. Catalog path is operator-supplied via CLI flag, not user input — no traversal risk. Translator built once at startup; map lookups O(1). Negligible runtime cost.

Recommendations

1. Split PR: localization vs YAML panic fix.
2. Drop variadic TranslatorConfig; use pointer or options.
3. Rename MustNewTranslator → NewTranslatorOrDefault and log fallback.
4. Apply recover() wrapper to parseCatalog for custom catalog symmetry.
5. Rewrite PR body to describe feature scope.
6. Native Spanish review of PR/MR labels and policy_check title.

[GMartinez-Sisti]

Regarding the approach, supporting the same templates for different languages seems like it's going to be a hassle to manage and error prone. A common approach is to only manage the localization strings in a single file per language and the templating would be similar for all. What do you think of this logic?