libgo/go/cmd/go/internal/load/flag.go

   1 // Copyright 2017 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package load
   6
   7 import (
   8         "cmd/go/internal/base"
   9         "cmd/go/internal/str"
  10         "fmt"
  11         "strings"
  12 )
  13
  14 var (
  15         BuildAsmflags   PerPackageFlag // -asmflags
  16         BuildGcflags    PerPackageFlag // -gcflags
  17         BuildLdflags    PerPackageFlag // -ldflags
  18         BuildGccgoflags PerPackageFlag // -gccgoflags
  19 )
  20
  21 // A PerPackageFlag is a command-line flag implementation (a flag.Value)
  22 // that allows specifying different effective flags for different packages.
  23 // See 'go help build' for more details about per-package flags.
  24 type PerPackageFlag struct {
  25         present bool
  26         values  []ppfValue
  27 }
  28
  29 // A ppfValue is a single <pattern>=<flags> per-package flag value.
  30 type ppfValue struct {
  31         match func(*Package) bool // compiled pattern
  32         flags []string
  33 }
  34
  35 // Set is called each time the flag is encountered on the command line.
  36 func (f *PerPackageFlag) Set(v string) error {
  37         return f.set(v, base.Cwd)
  38 }
  39
  40 // set is the implementation of Set, taking a cwd (current working directory) for easier testing.
  41 func (f *PerPackageFlag) set(v, cwd string) error {
  42         f.present = true
  43         match := func(p *Package) bool { return p.Internal.CmdlinePkg || p.Internal.CmdlineFiles } // default predicate with no pattern
  44         // For backwards compatibility with earlier flag splitting, ignore spaces around flags.
  45         v = strings.TrimSpace(v)
  46         if v == "" {
  47                 // Special case: -gcflags="" means no flags for command-line arguments
  48                 // (overrides previous -gcflags="-whatever").
  49                 f.values = append(f.values, ppfValue{match, []string{}})
  50                 return nil
  51         }
  52         if !strings.HasPrefix(v, "-") {
  53                 i := strings.Index(v, "=")
  54                 if i < 0 {
  55                         return fmt.Errorf("missing =<value> in <pattern>=<value>")
  56                 }
  57                 if i == 0 {
  58                         return fmt.Errorf("missing <pattern> in <pattern>=<value>")
  59                 }
  60                 pattern := strings.TrimSpace(v[:i])
  61                 match = MatchPackage(pattern, cwd)
  62                 v = v[i+1:]
  63         }
  64         flags, err := str.SplitQuotedFields(v)
  65         if err != nil {
  66                 return err
  67         }
  68         if flags == nil {
  69                 flags = []string{}
  70         }
  71         f.values = append(f.values, ppfValue{match, flags})
  72         return nil
  73 }
  74
  75 // String is required to implement flag.Value.
  76 // It is not used, because cmd/go never calls flag.PrintDefaults.
  77 func (f *PerPackageFlag) String() string { return "<PerPackageFlag>" }
  78
  79 // Present reports whether the flag appeared on the command line.
  80 func (f *PerPackageFlag) Present() bool {
  81         return f.present
  82 }
  83
  84 // For returns the flags to use for the given package.
  85 func (f *PerPackageFlag) For(p *Package) []string {
  86         flags := []string{}
  87         for _, v := range f.values {
  88                 if v.match(p) {
  89                         flags = v.flags
  90                 }
  91         }
  92         return flags
  93 }