golangci/golangci-lint · error

format source: %w

Error message

format source: %w

What it means

generateImports renders a synthetic Go source file (package main with blank imports of each plugin) and runs it through go/format.Source. The 'format source: %w' wrap means the rendered bytes are not valid Go syntax. This happens when a plugin's Import string is empty or malformed, producing an invalid import line like `_ ""`.

Source

Thrown at pkg/commands/internal/imports.go:65

	if err != nil {
		return nil, fmt.Errorf("parse template: %w", err)
	}

	var imps []string
	for _, plugin := range cfg.Plugins {
		imps = append(imps, plugin.Import)
	}

	buf := &bytes.Buffer{}

	err = impTmpl.Execute(buf, map[string]any{"Imports": imps})
	if err != nil {
		return nil, fmt.Errorf("execute template: %w", err)
	}

	source, err := format.Source(buf.Bytes())
	if err != nil {
		return nil, fmt.Errorf("format source: %w", err)
	}

	return source, nil
}

View on GitHub (pinned to ed7a235d2d)

Solutions

1. Read the wrapped go/format error: it reports the line/column offset in the generated source; run the builder with debug logging to see the generated source (updatePluginsFile logs it after successful generation)
2. Check the configuration's plugins entries for empty or invalid Import values and correct them
3. Run gofmt on the failing snippet locally to confirm the syntax problem
4. Add validation that skips/errors on plugins with empty Import before rendering

Example fix

// before (bad config)
plugins:
  - module: golangci-lint-plugin-example
    # import missing -> renders `_ ""`
// after
plugins:
  - module: golangci-lint-plugin-example
    import: github.com/org/golangci-lint-plugin-example/pkg/plugin

// validate plugin import paths before calling generateImports
for _, p := range cfg.Plugins {
    if p.Import == "" {
        return fmt.Errorf("plugin %q has empty import path", p.Module)
    }
    if !importPathRe.MatchString(p.Import) {
        return fmt.Errorf("plugin import %q is not a valid module path", p.Import)
    }
}
var importPathRe = regexp.MustCompile(`^[a-zA-Z0-9._~/-]+$`)

source, err := generateImports(cfg)
if err != nil {
    if strings.Contains(err.Error(), "format source") {
        // log cfg.Plugins so the offending import path is visible
    }
    return err
}

When it happens

Trigger: updatePluginsFile is called with a Configuration whose Plugins list contains an entry with an empty or syntactically invalid Import path, so the generated `import ( _ "..." )` block fails gofmt parsing.

Common situations: A misconfigured plugin entry in the builder configuration (missing import path, typo like a space or invalid characters in the module path), or an empty plugin struct appended to cfg.Plugins.

Related errors

• execute template: %w
• parsing %s: %w
• printing %s: %w
• formatting %s: %w
• %s: invalid configuration: %w

AI-assisted analysis of golangci/golangci-lint@ed7a235d2d (2026-09-02). Data as JSON: /api/errors/821d5cbcc3f61bc4. Report an issue: GitHub.