func filterImports()

in unix/internal/mkmerge/mkmerge.go [351:418]
54 lines of code
14 McCabe index (conditional complexity)

func filterImports(fileSrc []byte) ([]byte, error) {
	fset := token.NewFileSet()
	file, err := parser.ParseFile(fset, "", fileSrc, parser.ParseComments)
	if err != nil {
		return nil, err
	}
	cmap := ast.NewCommentMap(fset, file, file.Comments)

	// create set of references to imported identifiers
	keepImport := make(map[string]bool)
	for _, u := range file.Unresolved {
		keepImport[u.Name] = true
	}

	// filter import declarations
	decls := file.Decls
	file.Decls = file.Decls[:0]
	for _, decl := range decls {
		importDecl, ok := decl.(*ast.GenDecl)

		// Keep non-import declarations
		if !ok || importDecl.Tok != token.IMPORT {
			file.Decls = append(file.Decls, decl)
			continue
		}

		// Filter the import specs
		specs := importDecl.Specs
		importDecl.Specs = importDecl.Specs[:0]
		for _, spec := range specs {
			iSpec := spec.(*ast.ImportSpec)
			name, err := importName(iSpec)
			if err != nil {
				return nil, err
			}

			if keepImport[name] {
				importDecl.Specs = append(importDecl.Specs, iSpec)
			}
		}
		if len(importDecl.Specs) > 0 {
			file.Decls = append(file.Decls, importDecl)
		}
	}

	// filter file.Imports
	imports := file.Imports
	file.Imports = file.Imports[:0]
	for _, spec := range imports {
		name, err := importName(spec)
		if err != nil {
			return nil, err
		}

		if keepImport[name] {
			file.Imports = append(file.Imports, spec)
		}
	}
	file.Comments = cmap.Filter(file).Comments()

	var buf bytes.Buffer
	err = format.Node(&buf, fset, file)
	if err != nil {
		return nil, err
	}

	return buf.Bytes(), nil
}