unexported.go

package main

import (
	"fmt"
	"go/ast"
	"log"
	"unicode"
	"unicode/utf8"
)

// Note: the code in this file is borrowed from the Go project.
// It is licensed under a BSD-style license that is available
// at https://golang.org/LICENSE.
//
// Copyright 2015 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.

// trimUnexportedElems modifies spec in place to elide unexported fields from
// structs and methods from interfaces (unless the unexported flag is set).
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)
	}
}

// trimUnexportedFields returns the field list trimmed of unexported fields.
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)
}