Adds MergeConfig functionality

This patch adds the `MergeConfig` and `MergeInConfig` functions to
enable reading new configuration files via a merge strategy rather
than replace. For example, take the following as the base YAML for a
configuration:

    hello:
        pop: 37890
        world:
        - us
        - uk
        - fr
        - de

Now imagine we want to read the following, new configuration data:

    hello:
        pop: 45000
        universe:
        - mw
        - ad
    fu: bar

Using the standard `ReadConfig` function the value returned by the
nested key `hello.world` would no longer be present after the second
configuration is read. This is because the `ReadConfig` function and
its relatives replace nested structures entirely.

The new `MergeConfig` function would produce the following config
after the second YAML snippet was merged with the first:

    hello:
        pop: 45000
        world:
        - us
        - uk
        - fr
        - de
        universe:
        - mw
        - ad
    fu: bar

Examples showing how this works can be found in the two unit tests
named `TestMergeConfig` and `TestMergeConfigNoMerge`.
This commit is contained in:
akutz 2015-11-12 14:20:40 -06:00
parent e37b56e207
commit a9f31dbe0c
2 changed files with 211 additions and 0 deletions

112
viper.go
View file

@ -858,12 +858,124 @@ func (v *Viper) ReadInConfig() error {
return v.unmarshalReader(bytes.NewReader(file), v.config)
}
// MergeInConfig merges a new configuration with an existing config.
func MergeInConfig() error { return v.MergeInConfig() }
func (v *Viper) MergeInConfig() error {
jww.INFO.Println("Attempting to merge in config file")
if !stringInSlice(v.getConfigType(), SupportedExts) {
return UnsupportedConfigError(v.getConfigType())
}
file, err := ioutil.ReadFile(v.getConfigFile())
if err != nil {
return err
}
return v.MergeConfig(bytes.NewReader(file))
}
// Viper will read a configuration file, setting existing keys to nil if the
// key does not exist in the file.
func ReadConfig(in io.Reader) error { return v.ReadConfig(in) }
func (v *Viper) ReadConfig(in io.Reader) error {
v.config = make(map[string]interface{})
return v.unmarshalReader(in, v.config)
}
// MergeConfig merges a new configuration with an existing config.
func MergeConfig(in io.Reader) error { return v.MergeConfig(in) }
func (v *Viper) MergeConfig(in io.Reader) error {
if v.config == nil {
v.config = make(map[string]interface{})
}
cfg := make(map[string]interface{})
if err := v.unmarshalReader(in, cfg); err != nil {
return err
}
mergeMaps(cfg, v.config, nil)
return nil
}
func keyExists(k string, m map[string]interface{}) string {
lk := strings.ToLower(k)
for mk := range m {
lmk := strings.ToLower(mk)
if lmk == lk {
return mk
}
}
return ""
}
func castToMapStringInterface(
src map[interface{}]interface{}) map[string]interface{} {
tgt := map[string]interface{}{}
for k, v := range src {
tgt[fmt.Sprintf("%v", k)] = v
}
return tgt
}
// mergeMaps merges two maps. The `itgt` parameter is for handling go-yaml's
// insistence on parsing nested structures as `map[interface{}]interface{}`
// instead of using a `string` as the key for nest structures beyond one level
// deep. Both map types are supported as there is a go-yaml fork that uses
// `map[string]interface{}` instead.
func mergeMaps(
src, tgt map[string]interface{}, itgt map[interface{}]interface{}) {
for sk, sv := range src {
tk := keyExists(sk, tgt)
if tk == "" {
jww.TRACE.Printf("tk=\"\", tgt[%s]=%v", sk, sv)
tgt[sk] = sv
if itgt != nil {
itgt[sk] = sv
}
continue
}
tv, ok := tgt[tk]
if !ok {
jww.TRACE.Printf("tgt[%s] != ok, tgt[%s]=%v", tk, sk, sv)
tgt[sk] = sv
if itgt != nil {
itgt[sk] = sv
}
continue
}
svType := reflect.TypeOf(sv)
tvType := reflect.TypeOf(tv)
if svType != tvType {
jww.ERROR.Printf(
"svType != tvType; key=%s, st=%v, tt=%v, sv=%v, tv=%v",
sk, svType, tvType, sv, tv)
continue
}
jww.TRACE.Printf("processing key=%s, st=%v, tt=%v, sv=%v, tv=%v",
sk, svType, tvType, sv, tv)
switch ttv := tv.(type) {
case map[interface{}]interface{}:
jww.TRACE.Printf("merging maps (must convert)")
tsv := sv.(map[interface{}]interface{})
ssv := castToMapStringInterface(tsv)
stv := castToMapStringInterface(ttv)
mergeMaps(ssv, stv, ttv)
case map[string]interface{}:
jww.TRACE.Printf("merging maps")
mergeMaps(sv.(map[string]interface{}), ttv, nil)
default:
jww.TRACE.Printf("setting value")
tgt[tk] = sv
if itgt != nil {
itgt[tk] = sv
}
}
}
}
// func ReadBufConfig(buf *bytes.Buffer) error { return v.ReadBufConfig(buf) }
// func (v *Viper) ReadBufConfig(buf *bytes.Buffer) error {
// v.config = make(map[string]interface{})

View file

@ -652,3 +652,102 @@ func TestWrongDirsSearchNotFound(t *testing.T) {
// been ignored by the client, the default still loads
assert.Equal(t, `default`, v.GetString(`key`))
}
var yamlMergeExampleTgt = []byte(`
hello:
pop: 37890
world:
- us
- uk
- fr
- de
`)
var yamlMergeExampleSrc = []byte(`
hello:
pop: 45000
universe:
- mw
- ad
fu: bar
`)
func TestMergeConfig(t *testing.T) {
v := New()
v.SetConfigType("yml")
if err := v.ReadConfig(bytes.NewBuffer(yamlMergeExampleTgt)); err != nil {
t.Fatal(err)
}
if pop := v.GetInt("hello.pop"); pop != 37890 {
t.Fatalf("pop != 37890, = %d", pop)
}
if world := v.GetStringSlice("hello.world"); len(world) != 4 {
t.Fatalf("len(world) != 4, = %d", len(world))
}
if fu := v.GetString("fu"); fu != "" {
t.Fatalf("fu != \"\", = %s", fu)
}
if err := v.MergeConfig(bytes.NewBuffer(yamlMergeExampleSrc)); err != nil {
t.Fatal(err)
}
if pop := v.GetInt("hello.pop"); pop != 45000 {
t.Fatalf("pop != 45000, = %d", pop)
}
if world := v.GetStringSlice("hello.world"); len(world) != 4 {
t.Fatalf("len(world) != 4, = %d", len(world))
}
if universe := v.GetStringSlice("hello.universe"); len(universe) != 2 {
t.Fatalf("len(universe) != 2, = %d", len(universe))
}
if fu := v.GetString("fu"); fu != "bar" {
t.Fatalf("fu != \"bar\", = %s", fu)
}
}
func TestMergeConfigNoMerge(t *testing.T) {
v := New()
v.SetConfigType("yml")
if err := v.ReadConfig(bytes.NewBuffer(yamlMergeExampleTgt)); err != nil {
t.Fatal(err)
}
if pop := v.GetInt("hello.pop"); pop != 37890 {
t.Fatalf("pop != 37890, = %d", pop)
}
if world := v.GetStringSlice("hello.world"); len(world) != 4 {
t.Fatalf("len(world) != 4, = %d", len(world))
}
if fu := v.GetString("fu"); fu != "" {
t.Fatalf("fu != \"\", = %s", fu)
}
if err := v.ReadConfig(bytes.NewBuffer(yamlMergeExampleSrc)); err != nil {
t.Fatal(err)
}
if pop := v.GetInt("hello.pop"); pop != 45000 {
t.Fatalf("pop != 45000, = %d", pop)
}
if world := v.GetStringSlice("hello.world"); len(world) != 0 {
t.Fatalf("len(world) != 0, = %d", len(world))
}
if universe := v.GetStringSlice("hello.universe"); len(universe) != 2 {
t.Fatalf("len(universe) != 2, = %d", len(universe))
}
if fu := v.GetString("fu"); fu != "bar" {
t.Fatalf("fu != \"bar\", = %s", fu)
}
}