Documentation
¶
Overview ¶
Package printer implements printing of AST nodes.
Index ¶
Examples ¶
Constants ¶
const (
SeeNext = -32768
)
Variables ¶
This section is empty.
Functions ¶
func Fprint ¶
func Fprint(formatOptions *FormatOptions, src []byte, output io.Writer, fset *token.FileSet, node interface{}) error
Fprint "pretty-prints" an AST node to output for a given set of formatOptions. 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. src is the source code from which fset is derived.
formatOptions:
- formatOptions must not be nil.
- The last entry in the formatOptions linked list must have all fields != SeeNext.
Example ¶
package main
import (
"bytes"
"fmt"
"go/ast"
"go/parser"
"go/token"
"strings"
"winterdrache.de/goformat/printer"
)
func parseFunc(filename, functionname string) (fun *ast.FuncDecl, fset *token.FileSet) {
fset = token.NewFileSet()
if file, err := parser.ParseFile(fset, filename, nil, 0); err == nil {
for _, d := range file.Decls {
if f, ok := d.(*ast.FuncDecl); ok && f.Name.Name == functionname {
fun = f
return
}
}
}
panic("function not found")
}
func main() {
// 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)
Types ¶
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 Context ¶
type Context uint
A Context is a set of flags, set depending on what's currently being printed. The user can specify different formatting options depending on context. If multiple flags are asserted that means the context is the intersection of these flags, e.g. CtxFileHeader|CtxBlockComment means a block comment in the file's header area. Some flags are mutually exclusive, e.g. CtxLineComment and CtxBlockComment.
type FormatOptions ¶
type FormatOptions struct {
Next *FormatOptions // next (lower priority) in the chain of options
Context // which context these options apply to
Mode Mode // default: 0, SeeNext => unset, use Next
Tabwidth int // default: 8, this is the width of 1 indentation step, SeeNext => unset, use Next
Indent int // default: 0 (add this many Tabwidth sized indents before each line), SeeNext => unset, use Next
Column int // default: 0, min width of columns for alignment (excluding indentation which is Tabwidth)
Pad int // default: 1, number of spaces to add to each column (except indentation)
Shift int // default: 0, number of spaces to add after indentation
Enter0 int // default: 0, indent steps for blocks that gofmt has a default of 0 for
Enter int // default: 1, indent steps for blocks that gofmt has a default of 1 for
InlineBlocks int // default: 0 (always insert newline after { and before }, 1: respect original formatting
}
A FormatOptions node controls the output of Fprint.
func FormatOptionsDefault ¶
func FormatOptionsDefault() *FormatOptions
func FormatOptionsUninitialized ¶
func FormatOptionsUninitialized() *FormatOptions
func ParseStyle ¶
func ParseStyle(style string) (*FormatOptions, error)
Parses a style definition into a linked list of FormatOptions. The last entry in the list is always complete, i.e. has no SeeNext fields.
func (*FormatOptions) Equals ¶
func (fo *FormatOptions) Equals(fo2 *FormatOptions) bool
Returns true iff the formatting fields of fo and fo2 are equal. Context and Next links are ignored.
func (*FormatOptions) ForContext ¶
func (fo *FormatOptions) ForContext(ctx Context) *FormatOptions
Returns a complete set (i.e. without SeeNext entries) of FormatOptions for the given context.
func (*FormatOptions) TabWriterOptions ¶
func (cfg *FormatOptions) TabWriterOptions() (minwidth, minwidth_empty, tabwidth, padding int, padchar byte, twmode uint)
Returns arguments for tabwriter.NewWriter() corresponding to these FormatOptions
type Mode ¶
type Mode int
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 KeepIndent // (overrides TabIndent) use original indentation from source NoIndent // (overrides TabIndent/KeepIndent but not FormatOptions.Indent) left-align all lines )
Source Files