format.go

package main

import (
	"bytes"
	"fmt"
	"github.com/JohnWall2016/gogetdef/types"
	"go/ast"
	"go/printer"
	"go/token"
	"unicode"
	"unicode/utf8"
)

func trimUnexportedElems(spec *ast.TypeSpec) {
	switch typ := spec.Type.(type) {
	case *ast.StructType:
		typ.Fields = trimUnexportedFields(typ.Fields, false)
	case *ast.InterfaceType:
		typ.Methods = trimUnexportedFields(typ.Methods, true)
	}
}

func trimUnexportedFields(fields *ast.FieldList, isInterface bool) *ast.FieldList {
	what := "methods"
	if !isInterface {
		what = "fields"
	}

	trimmed := false
	list := make([]*ast.Field, 0, len(fields.List))
	for _, field := range fields.List {
		names := field.Names
		if len(names) == 0 {
			// Embedded type. Use the name of the type. It must be of type ident or *ident.
			// Nothing else is allowed.
			switch ident := field.Type.(type) {
			case *ast.Ident:
				if isInterface && ident.Name == "error" && ident.Obj == nil {
					// For documentation purposes, we consider the builtin error
					// type special when embedded in an interface, such that it
					// always gets shown publicly.
					list = append(list, field)
					continue
				}
				names = []*ast.Ident{ident}
			case *ast.StarExpr:
				// Must have the form *identifier.
				// This is only valid on embedded types in structs.
				if ident, ok := ident.X.(*ast.Ident); ok && !isInterface {
					names = []*ast.Ident{ident}
				}
			case *ast.SelectorExpr:
				// An embedded type may refer to a type in another package.
				names = []*ast.Ident{ident.Sel}
			}
			if names == nil {
				// Can only happen if AST is incorrect. Safe to continue with a nil list.
				//log.Print("invalid program: unexpected type for embedded field")
			}
		}
		// Trims if any is unexported. Good enough in practice.
		ok := true
		for _, name := range names {
			if !isUpper(name.Name) {
				trimmed = true
				ok = false
				break
			}
		}
		if ok {
			list = append(list, field)
		}
	}
	if !trimmed {
		return fields
	}
	unexportedField := &ast.Field{
		Type: &ast.Ident{
			// Hack: printer will treat this as a field with a named type.
			// Setting Name and NamePos to ("", fields.Closing-1) ensures that
			// when Pos and End are called on this field, they return the
			// position right before closing '}' character.
			Name:    "",
			NamePos: fields.Closing - 1,
		},
		Comment: &ast.CommentGroup{
			List: []*ast.Comment{{Text: fmt.Sprintf("// Has unexported %s.\n", what)}},
		},
	}
	return &ast.FieldList{
		Opening: fields.Opening,
		List:    append(list, unexportedField),
		Closing: fields.Closing,
	}
}

// isUpper reports whether the name starts with an upper case letter.
func isUpper(name string) bool {
	ch, _ := utf8.DecodeRuneInString(name)
	return unicode.IsUpper(ch)
}

func formatNode(n ast.Node, obj types.Object, fset *token.FileSet, showUnexported bool) string {
	//fmt.Printf("formatting %T node\n", n)
	var nc ast.Node
	// Render a copy of the node with no documentation.
	// We emit the documentation ourself.
	switch n := n.(type) {
	case *ast.FuncDecl:
		cp := *n
		cp.Doc = nil
		// Don't print the whole function body
		cp.Body = nil
		nc = &cp
	case *ast.Field:
		// Not supported by go/printer

		// TODO(dominikh): Methods in interfaces are syntactically
		// represented as fields. Using types.Object.String for those
		// causes them to look different from real functions.
		// go/printer doesn't include the import paths in names, while
		// Object.String does. Fix that.

		return obj.String()
	case *ast.TypeSpec:
		specCp := *n
		if showUnexported == false {
			trimUnexportedElems(&specCp)
		}
		specCp.Doc = nil
		typeSpec := ast.GenDecl{
			Tok:   token.TYPE,
			Specs: []ast.Spec{&specCp},
		}
		nc = &typeSpec
	case *ast.GenDecl:
		cp := *n
		cp.Doc = nil
		if len(n.Specs) > 0 {
			// Only print this one type, not all the types in the gendecl
			switch n.Specs[0].(type) {
			case *ast.TypeSpec:
				spec := findTypeSpec(n, obj.Pos())
				if spec != nil {
					specCp := *spec
					if showUnexported == false {
						trimUnexportedElems(&specCp)
					}
					specCp.Doc = nil
					cp.Specs = []ast.Spec{&specCp}
				}
				cp.Lparen = 0
				cp.Rparen = 0
			case *ast.ValueSpec:
				spec := findVarSpec(n, obj.Pos())
				if spec != nil {
					specCp := *spec
					specCp.Doc = nil
					cp.Specs = []ast.Spec{&specCp}
				}
				cp.Lparen = 0
				cp.Rparen = 0
			}
		}
		nc = &cp

	default:
		return obj.String()
	}

	buf := &bytes.Buffer{}
	cfg := printer.Config{Mode: printer.UseSpaces | printer.TabIndent, Tabwidth: 8}
	err := cfg.Fprint(buf, fset, nc)
	if err != nil {
		return obj.String()
	}
	return buf.String()
}

func findTypeSpec(decl *ast.GenDecl, pos token.Pos) *ast.TypeSpec {
	for _, spec := range decl.Specs {
		typeSpec := spec.(*ast.TypeSpec)
		if typeSpec.Pos() == pos {
			return typeSpec
		}
	}
	return nil
}

func findVarSpec(decl *ast.GenDecl, pos token.Pos) *ast.ValueSpec {
	for _, spec := range decl.Specs {
		varSpec := spec.(*ast.ValueSpec)
		for _, ident := range varSpec.Names {
			if ident.Pos() == pos {
				return varSpec
			}
		}
	}
	return nil
}