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 cache
6 7 import (
8 "fmt"
9 "log"
10 "os"
11 "path/filepath"
12 "sync"
13 )
14 15 // Default returns the default cache to use.
16 func Default() (*Cache, error) {
17 defaultOnce.Do(initDefaultCache)
18 return defaultCache, defaultDirErr
19 }
20 21 var (
22 defaultOnce sync.Once
23 defaultCache *Cache
24 )
25 26 // cacheREADME is a message stored in a README in the cache directory.
27 // Because the cache lives outside the normal Go trees, we leave the
28 // README as a courtesy to explain where it came from.
29 const cacheREADME = `This directory holds cached build artifacts from staticcheck.
30 `
31 32 // initDefaultCache does the work of finding the default cache
33 // the first time Default is called.
34 func initDefaultCache() {
35 dir := DefaultDir()
36 if err := os.MkdirAll(dir, 0777); err != nil {
37 log.Fatalf("failed to initialize build cache at %s: %s\n", dir, err)
38 }
39 if _, err := os.Stat(filepath.Join(dir, "README")); err != nil {
40 // Best effort.
41 os.WriteFile(filepath.Join(dir, "README"), []byte(cacheREADME), 0666)
42 }
43 44 c, err := Open(dir)
45 if err != nil {
46 log.Fatalf("failed to initialize build cache at %s: %s\n", dir, err)
47 }
48 defaultCache = c
49 }
50 51 var (
52 defaultDirOnce sync.Once
53 defaultDir string
54 defaultDirErr error
55 )
56 57 // DefaultDir returns the effective STATICCHECK_CACHE setting.
58 func DefaultDir() string {
59 // Save the result of the first call to DefaultDir for later use in
60 // initDefaultCache. cmd/go/main.go explicitly sets GOCACHE so that
61 // subprocesses will inherit it, but that means initDefaultCache can't
62 // otherwise distinguish between an explicit "off" and a UserCacheDir error.
63 64 defaultDirOnce.Do(func() {
65 defaultDir = os.Getenv("STATICCHECK_CACHE")
66 if filepath.IsAbs(defaultDir) {
67 return
68 }
69 if defaultDir != "" {
70 defaultDirErr = fmt.Errorf("STATICCHECK_CACHE is not an absolute path")
71 return
72 }
73 74 // Compute default location.
75 dir, err := os.UserCacheDir()
76 if err != nil {
77 defaultDirErr = fmt.Errorf("STATICCHECK_CACHE is not defined and %v", err)
78 return
79 }
80 defaultDir = filepath.Join(dir, "staticcheck")
81 })
82 83 return defaultDir
84 }
85