package printer
import "go/printer"
Package printer implements printing of AST nodes..
Index
- func Fprint(output io.Writer, fset *token.FileSet, node interface{}) error
- type CommentedNode
- type Config
- func (cfg *Config) Fprint(output io.Writer, fset *token.FileSet, node interface{}) error
- type Mode
func Fprint
func Fprint(output io.Writer, fset *token.FileSet, node interface{}) error
Fprint "pretty-prints" an AST node to output. It calls Config.Fprint with default settings.
// Parse source file and extract the AST without comments for
// this function, with position information referring to the
// file set fset.
funcAST, fset := parseFunc("example_test.go", "ExampleFprint")
// Print the function body into buffer buf.
// The file set is provided to the printer so that it knows
// about the original source formatting and can add additional
// line breaks where they were present in the source.
var buf bytes.Buffer
printer.Fprint(&buf, fset, funcAST.Body)
// Remove braces {} enclosing the function body, unindent,
// and trim leading and trailing white space.
s := buf.String()
s = s[1 : len(s)-1]
s = strings.TrimSpace(strings.Replace(s, "\n\t", "\n", -1))
// Print the cleaned-up body text to stdout.
fmt.Println(s)
Output:
funcAST, fset := parseFunc("example_test.go", "ExampleFprint")
var buf bytes.Buffer
printer.Fprint(&buf, fset, funcAST.Body)
s := buf.String()
s = s[1 : len(s)-1]
s = strings.TrimSpace(strings.Replace(s, "\n\t", "\n", -1))
fmt.Println(s)
type CommentedNode
type CommentedNode struct {
Node interface{} // *ast.File, or ast.Expr, ast.Decl, ast.Spec, or ast.Stmt
Comments []*ast.CommentGroup
}
A CommentedNode bundles an AST node and corresponding comments. It may be provided as argument to any of the Fprint functions.
type Config
type Config struct {
Mode Mode // default: 0
Tabwidth int // default: 8
Indent int // default: 0 (all code is indented at least by this much)
}
A Config node controls the output of Fprint.
func (*Config) Fprint
func (cfg *Config) Fprint(output io.Writer, fset *token.FileSet, node interface{}) error
Fprint "pretty-prints" an AST node to output for a given configuration cfg. Position information is interpreted relative to the file set fset. The node type must be *ast.File, *CommentedNode, []ast.Decl, []ast.Stmt, or assignment-compatible to ast.Expr, ast.Decl, ast.Spec, or ast.Stmt.
type Mode
type Mode uint
A Mode value is a set of flags (or 0). They control printing.
const (
RawFormat Mode = 1 << iota // do not use a tabwriter; if set, UseSpaces is ignored
TabIndent // use tabs for indentation independent of UseSpaces
UseSpaces // use spaces instead of tabs for alignment
SourcePos // emit //line comments to preserve original source positions
)