file.go

// Copyright 2014 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 main

import (
	"go/ast"
	"go/constant"
	"go/token"
	"go/types"
	"log"
	"strings"
)

// File holds a single parsed file and associated data.
type File struct {
	pkg  *Package  // Package to which this file belongs.
	file *ast.File // Parsed AST.
	// These fields are reset for each type being generated.
	typeName string  // Name of the constant type.
	values   []Value // Accumulator for constant values of that type.

	trimPrefix  string
	lineComment bool

	nameTransform _TextConvertTo
}

// genDecl processes one declaration clause.
func (f *File) genDecl(node ast.Node) bool {
	decl, ok := node.(*ast.GenDecl)
	if !ok || decl.Tok != token.CONST {
		// We only care about const declarations.
		return true
	}
	// The name of the type of the constants we are declaring.
	// Can change if this is a multi-element declaration.
	typ := ""
	// Loop over the elements of the declaration. Each element is a ValueSpec:
	// a list of names possibly followed by a type, possibly followed by values.
	// If the type and value are both missing, we carry down the type (and value,
	// but the "go/types" package takes care of that).
	for _, spec := range decl.Specs {
		vspec := spec.(*ast.ValueSpec) // Guaranteed to succeed as this is CONST.
		if vspec.Type == nil && len(vspec.Values) > 0 {
			// "X = 1". With no type but a value. If the constant is untyped,
			// skip this vspec and reset the remembered type.
			typ = ""

			// If this is a simple type conversion, remember the type.
			// We don't mind if this is actually a call; a qualified call won't
			// be matched (that will be SelectorExpr, not Ident), and only unusual
			// situations will result in a function call that appears to be
			// a type conversion.
			ce, ok := vspec.Values[0].(*ast.CallExpr)
			if !ok {
				continue
			}
			id, ok := ce.Fun.(*ast.Ident)
			if !ok {
				continue
			}
			typ = id.Name
		}
		if vspec.Type != nil {
			// "X T". We have a type. Remember it.
			ident, ok := vspec.Type.(*ast.Ident)
			if !ok {
				continue
			}
			typ = ident.Name
		}
		if typ != f.typeName {
			// This is not the type we're looking for.
			continue
		}
		// We now have a list of names (from one line of source code) all being
		// declared with the desired type.
		// Grab their names and actual values and store them in f.values.
		for _, name := range vspec.Names {
			if name.Name == "_" {
				continue
			}
			// This dance lets the type checker find the values for us. It's a
			// bit tricky: look up the object declared by the name, find its
			// types.Const, and extract its value.
			obj, ok := f.pkg.defs[name]
			if !ok {
				log.Fatalf("no value for constant %s", name)
			}
			info := obj.Type().Underlying().(*types.Basic).Info()
			if info&types.IsInteger == 0 {
				log.Fatalf("can't handle non-integer constant type %s", typ)
			}
			value := obj.(*types.Const).Val() // Guaranteed to succeed as this is CONST.
			if value.Kind() != constant.Int {
				log.Fatalf("can't happen: constant is not an integer %s", name)
			}
			i64, isInt := constant.Int64Val(value)
			u64, isUint := constant.Uint64Val(value)
			if !isInt && !isUint {
				log.Fatalf("internal error: value of %s is not an integer: %s", name, value.String())
			}
			if !isInt {
				u64 = uint64(i64)
			}
			v := Value{
				originalName: name.Name,
				value:        u64,
				signed:       info&types.IsUnsigned == 0,
				str:          value.String(),
			}
			if c := vspec.Comment; f.lineComment && c != nil && len(c.List) == 1 {
				v.name = strings.TrimSpace(c.Text())
			} else {
				v.name = strings.TrimPrefix(v.originalName, f.trimPrefix)
				v.name = transformTextTo(f.nameTransform, v.name)
			}
			f.values = append(f.values, v)
		}
	}
	return false
}