| // Copyright 2012 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // Package format implements standard formatting of Go source. |
| // |
| // Note that formatting of Go source code changes over time, so tools relying on |
| // consistent formatting should execute a specific version of the gofmt binary |
| // instead of using this package. That way, the formatting will be stable, and |
| // the tools won't need to be recompiled each time gofmt changes. |
| // |
| // For example, pre-submit checks that use this package directly would behave |
| // differently depending on what Go version each developer uses, causing the |
| // check to be inherently fragile. |
| package format |
| |
| import ( |
| "bytes" |
| "fmt" |
| "go/ast" |
| "go/parser" |
| "go/printer" |
| "go/token" |
| "io" |
| ) |
| |
| // Keep these in sync with cmd/gofmt/gofmt.go. |
| const ( |
| tabWidth = 8 |
| printerMode = printer.UseSpaces | printer.TabIndent | printerNormalizeNumbers |
| |
| // printerNormalizeNumbers means to canonicalize number literal prefixes |
| // and exponents while printing. See https://golang.org/doc/go1.13#gofmt. |
| // |
| // This value is defined in go/printer specifically for go/format and cmd/gofmt. |
| printerNormalizeNumbers = 1 << 30 |
| ) |
| |
| var config = printer.Config{Mode: printerMode, Tabwidth: tabWidth} |
| |
| const parserMode = parser.ParseComments |
| |
| // Node formats node in canonical gofmt style and writes the result to dst. |
| // |
| // The node type must be *ast.File, *printer.CommentedNode, []ast.Decl, |
| // []ast.Stmt, or assignment-compatible to ast.Expr, ast.Decl, ast.Spec, |
| // or ast.Stmt. Node does not modify node. Imports are not sorted for |
| // nodes representing partial source files (for instance, if the node is |
| // not an *ast.File or a *printer.CommentedNode not wrapping an *ast.File). |
| // |
| // The function may return early (before the entire result is written) |
| // and return a formatting error, for instance due to an incorrect AST. |
| // |
| func Node(dst io.Writer, fset *token.FileSet, node interface{}) error { |
| // Determine if we have a complete source file (file != nil). |
| var file *ast.File |
| var cnode *printer.CommentedNode |
| switch n := node.(type) { |
| case *ast.File: |
| file = n |
| case *printer.CommentedNode: |
| if f, ok := n.Node.(*ast.File); ok { |
| file = f |
| cnode = n |
| } |
| } |
| |
| // Sort imports if necessary. |
| if file != nil && hasUnsortedImports(file) { |
| // Make a copy of the AST because ast.SortImports is destructive. |
| // TODO(gri) Do this more efficiently. |
| var buf bytes.Buffer |
| err := config.Fprint(&buf, fset, file) |
| if err != nil { |
| return err |
| } |
| file, err = parser.ParseFile(fset, "", buf.Bytes(), parserMode) |
| if err != nil { |
| // We should never get here. If we do, provide good diagnostic. |
| return fmt.Errorf("format.Node internal error (%s)", err) |
| } |
| ast.SortImports(fset, file) |
| |
| // Use new file with sorted imports. |
| node = file |
| if cnode != nil { |
| node = &printer.CommentedNode{Node: file, Comments: cnode.Comments} |
| } |
| } |
| |
| return config.Fprint(dst, fset, node) |
| } |
| |
| // Source formats src in canonical gofmt style and returns the result |
| // or an (I/O or syntax) error. src is expected to be a syntactically |
| // correct Go source file, or a list of Go declarations or statements. |
| // |
| // If src is a partial source file, the leading and trailing space of src |
| // is applied to the result (such that it has the same leading and trailing |
| // space as src), and the result is indented by the same amount as the first |
| // line of src containing code. Imports are not sorted for partial source files. |
| // |
| func Source(src []byte) ([]byte, error) { |
| fset := token.NewFileSet() |
| file, sourceAdj, indentAdj, err := parse(fset, "", src, true) |
| if err != nil { |
| return nil, err |
| } |
| |
| if sourceAdj == nil { |
| // Complete source file. |
| // TODO(gri) consider doing this always. |
| ast.SortImports(fset, file) |
| } |
| |
| return format(fset, file, sourceAdj, indentAdj, src, config) |
| } |
| |
| func hasUnsortedImports(file *ast.File) bool { |
| for _, d := range file.Decls { |
| d, ok := d.(*ast.GenDecl) |
| if !ok || d.Tok != token.IMPORT { |
| // Not an import declaration, so we're done. |
| // Imports are always first. |
| return false |
| } |
| if d.Lparen.IsValid() { |
| // For now assume all grouped imports are unsorted. |
| // TODO(gri) Should check if they are sorted already. |
| return true |
| } |
| // Ungrouped imports are sorted by default. |
| } |
| return false |
| } |