fdroidcl: fix cache format crash with repo refs

The new cache format didn't encode the repos properly, which lead to
crashes. Since we're modifying the cache format, introduce a version and
discard all previous caches (defaulting to version 0).

Fixes #19.

cmd/fdroidcl/update.go

@@ -42,8 +42,8 @@ func runUpdate(args []string) {
 		}
 	}
 	if anyModified {
-		cache := filepath.Join(mustData(), "cache-gob")
-		os.Remove(cache)
+		cachePath := filepath.Join(mustData(), "cache-gob")
+		os.Remove(cachePath)
 	}
 }
 
@@ -143,12 +143,20 @@ func indexPath(name string) string {
 	return filepath.Join(mustData(), name+".jar")
 }
 
-func mustLoadIndexes() (apps []fdroidcl.App) {
-	cache := filepath.Join(mustData(), "cache-gob")
-	if f, err := os.Open(cache); err == nil {
+const cacheVersion = 1
+
+type cache struct {
+	Version int
+	Apps    []fdroidcl.App
+}
+
+func mustLoadIndexes() []fdroidcl.App {
+	cachePath := filepath.Join(mustData(), "cache-gob")
+	if f, err := os.Open(cachePath); err == nil {
 		defer f.Close()
-		if err := gob.NewDecoder(f).Decode(&apps); err == nil {
-			return
+		var c cache
+		if err := gob.NewDecoder(f).Decode(&c); err == nil && c.Version == cacheVersion {
+			return c.Apps
 		}
 	}
 	m := make(map[string]*fdroidcl.App)
@@ -175,14 +183,17 @@ func mustLoadIndexes() (apps []fdroidcl.App) {
 			m[app.ID].Apks = apks
 		}
 	}
-	apps = make([]fdroidcl.App, 0, len(m))
+	apps := make([]fdroidcl.App, 0, len(m))
 	for _, a := range m {
 		apps = append(apps, *a)
 	}
 	sort.Sort(fdroidcl.AppList(apps))
-	if f, err := os.Create(cache); err == nil {
+	if f, err := os.Create(cachePath); err == nil {
 		defer f.Close()
-		gob.NewEncoder(f).Encode(apps)
+		gob.NewEncoder(f).Encode(cache{
+			Version: cacheVersion,
+			Apps:    apps,
+		})
 	}
-	return
+	return apps
 }

index.go

@@ -86,7 +86,7 @@ func (a *App) IconURLForDensity(density IconDensity) string {
 	if len(a.Apks) == 0 {
 		return ""
 	}
-	return fmt.Sprintf("%s/%s/%s", a.Apks[0].repo.URL,
+	return fmt.Sprintf("%s/%s/%s", a.Apks[0].repoURL,
 		getIconsDir(density), a.Icon)
 }
 
@@ -195,16 +195,16 @@ type Apk struct {
 	Feats   CommaList `xml:"features"`
 	Hash    HexHash   `xml:"hash"`
 
-	AppID string `xml:"-"`
-	repo  *Repo  `xml:"-"`
+	AppID   string `xml:"-"`
+	repoURL string `xml:"-"`
 }
 
 func (a *Apk) URL() string {
-	return fmt.Sprintf("%s/%s", a.repo.URL, a.ApkName)
+	return fmt.Sprintf("%s/%s", a.repoURL, a.ApkName)
 }
 
 func (a *Apk) SrcURL() string {
-	return fmt.Sprintf("%s/%s", a.repo.URL, a.SrcName)
+	return fmt.Sprintf("%s/%s", a.repoURL, a.SrcName)
 }
 
 func (a *Apk) IsCompatibleABI(ABIs []string) bool {
@@ -260,7 +260,7 @@ func LoadIndexXML(r io.Reader) (*Index, error) {
 		for j := range app.Apks {
 			apk := &app.Apks[j]
 			apk.AppID = app.ID
-			apk.repo = &index.Repo
+			apk.repoURL = index.Repo.URL
 		}
 	}
 	return &index, nil