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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,128 @@ | ||
| package transform | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "reflect" | ||
|
|
||
| "github.com/fatih/structtag" | ||
| ) | ||
|
|
||
| const ( | ||
| dialsAliasTagSuffix = "alias" | ||
| aliasFieldSuffix = "_alias9wr876rw3" // a random string to append to the alias field to avoid collisions | ||
| ) | ||
|
|
||
| // AliasMangler manages aliases for dials, dialsenv, dialsflag, and dialspflag | ||
| // struct tags to make it possible to migrate from one name to another | ||
| // conveniently. | ||
| type AliasMangler struct{} | ||
|
|
||
| // Mangle implements the Mangler interface. If an alias tag is defined, the | ||
| // struct field will be copied with the non-aliased tag set to the alias's | ||
| // value. | ||
| func (a AliasMangler) Mangle(sf reflect.StructField) ([]reflect.StructField, error) { | ||
| sourceTags := []string{"dials", "dialsenv", "dialsflag", "dialspflag"} | ||
| originalVals := map[string]string{} | ||
| aliasVals := map[string]string{} | ||
|
|
||
| sfTags, parseErr := structtag.Parse(string(sf.Tag)) | ||
| if parseErr != nil { | ||
| return nil, fmt.Errorf("error parsing source tags %w", parseErr) | ||
| } | ||
|
|
||
| anyAliasFound := false | ||
| for _, tag := range sourceTags { | ||
| if originalVal, getErr := sfTags.Get(tag); getErr == nil { | ||
| originalVals[tag] = originalVal.Name | ||
| } | ||
|
|
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| if aliasVal, getErr := sfTags.Get(tag + dialsAliasTagSuffix); getErr == nil { | ||
| aliasVals[tag] = aliasVal.Name | ||
| anyAliasFound = true | ||
|
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||
| // remove the alias tag from the definition | ||
| sfTags.Delete(tag + dialsAliasTagSuffix) | ||
| } | ||
| } | ||
|
|
||
| if !anyAliasFound { | ||
| // we didn't find any aliases so just get out early | ||
| return []reflect.StructField{sf}, nil | ||
| } | ||
|
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| aliasField := sf | ||
| aliasField.Name += aliasFieldSuffix | ||
|
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| // now that we've copied it, reset the struct tags on the source field to | ||
| // not include the alias tags | ||
| sf.Tag = reflect.StructTag(sfTags.String()) | ||
|
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| tags, parseErr := structtag.Parse(string(aliasField.Tag)) | ||
| if parseErr != nil { | ||
| return nil, fmt.Errorf("error parsing struct tags: %w", parseErr) | ||
| } | ||
|
|
||
| for _, tag := range sourceTags { | ||
| // remove the alias tag so it's not left on the copied StructField | ||
| tags.Delete(tag + dialsAliasTagSuffix) | ||
|
|
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| if aliasVals[tag] == "" { | ||
| // if the particular flag isn't set at all just move on... | ||
| continue | ||
| } | ||
|
|
||
| newDialsTag := &structtag.Tag{ | ||
| Key: tag, | ||
| Name: aliasVals[tag], | ||
| } | ||
|
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| if setErr := tags.Set(newDialsTag); setErr != nil { | ||
| return nil, fmt.Errorf("error setting new value for dials tag: %w", setErr) | ||
| } | ||
|
|
||
| // update dialsdesc if there is one | ||
| if desc, getErr := tags.Get("dialsdesc"); getErr == nil { | ||
| newDesc := &structtag.Tag{ | ||
| Key: "dialsdesc", | ||
| Name: desc.Name + " (alias of `" + originalVals[tag] + "`)", | ||
| } | ||
| if setErr := tags.Set(newDesc); setErr != nil { | ||
| return nil, fmt.Errorf("error setting amended dialsdesc for tag %q: %w", tag, setErr) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // set the new flags on the alias field | ||
| aliasField.Tag = reflect.StructTag(tags.String()) | ||
|
|
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| return []reflect.StructField{sf, aliasField}, nil | ||
| } | ||
|
|
||
| // Unmangle implements the Mangler interface and unwinds the alias copying | ||
| // operation. Note that if both the source and alias are both set in the | ||
| // configuration, an error will be returned. | ||
| func (a AliasMangler) Unmangle(sf reflect.StructField, fvs []FieldValueTuple) (reflect.Value, error) { | ||
| if len(fvs) != 2 { | ||
| return reflect.Value{}, fmt.Errorf("expected 2 tuples, got %d", len(fvs)) | ||
| } | ||
|
|
||
| if !fvs[0].Value.IsNil() && !fvs[1].Value.IsNil() { | ||
| return reflect.Value{}, fmt.Errorf("both alias and original set for field %q", sf.Name) | ||
| } | ||
|
|
||
| for _, fv := range fvs { | ||
| if !fv.Value.IsNil() { | ||
| return fv.Value, nil | ||
| } | ||
| } | ||
|
|
||
| // if we made it this far, they were both nil, which is fine -- just return | ||
| // one of them. | ||
| return fvs[0].Value, nil | ||
| } | ||
|
|
||
| // ShouldRecurse is called after Mangle for each field so nested struct | ||
| // fields get iterated over after any transformation done by Mangle(). | ||
| func (a AliasMangler) ShouldRecurse(_ reflect.StructField) bool { | ||
| return true | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,148 @@ | ||
| package transform | ||
|
|
||
| import ( | ||
| "reflect" | ||
| "testing" | ||
|
|
||
| "github.com/fatih/structtag" | ||
| "github.com/stretchr/testify/assert" | ||
| "github.com/stretchr/testify/require" | ||
| ) | ||
|
|
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| func TestAliasManglerMangle(t *testing.T) { | ||
|
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||
| for testName, tbl := range map[string]struct { | ||
| tag string | ||
| expectedOrig map[string]string | ||
| expectedAlias map[string]string | ||
| }{ | ||
| "dialsOnly": { | ||
| tag: `dials:"name" dialsalias:"anothername"`, | ||
| expectedOrig: map[string]string{"dials": "name"}, | ||
| expectedAlias: map[string]string{"dials": "anothername"}, | ||
| }, | ||
| "withDialsDesc": { | ||
| tag: `dials:"name" dialsalias:"anothername" dialsdesc:"the name for this"`, | ||
| expectedOrig: map[string]string{"dials": "name", "dialsdesc": "the name for this"}, | ||
| expectedAlias: map[string]string{"dials": "anothername", "dialsdesc": "the name for this (alias of `name`)"}, | ||
| }, | ||
| "dialsDialsEnvFlagPFlag": { | ||
| tag: `dials:"name" dialsflag:"flagname" dialspflag:"pflagname" dialsenv:"envname" dialsalias:"anothername" dialsflagalias:"flagalias" dialspflagalias:"pflagalias" dialsenvalias:"envalias"`, | ||
| expectedOrig: map[string]string{"dials": "name", "dialsflag": "flagname", "dialspflag": "pflagname", "dialsenv": "envname"}, | ||
| expectedAlias: map[string]string{"dials": "anothername", "dialsflag": "flagalias", "dialspflag": "pflagalias", "dialsenv": "envalias"}, | ||
| }, | ||
| } { | ||
| t.Run(testName, func(t *testing.T) { | ||
| sf := reflect.StructField{ | ||
| Name: "Foo", | ||
| Type: reflect.TypeOf(""), | ||
| Tag: reflect.StructTag(tbl.tag), | ||
| } | ||
|
|
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| aliasMangler := AliasMangler{} | ||
| fields, mangleErr := aliasMangler.Mangle(sf) | ||
| require.NoError(t, mangleErr) | ||
|
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| require.Len(t, fields, 2) | ||
|
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| originalTags, parseErr := structtag.Parse(string(fields[0].Tag)) | ||
| require.NoError(t, parseErr) | ||
|
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| for k, v := range tbl.expectedOrig { | ||
| val, err := originalTags.Get(k) | ||
| require.NoError(t, err) | ||
| assert.Equal(t, v, val.Name) | ||
| } | ||
| assert.Equal(t, len(tbl.expectedOrig), originalTags.Len()) | ||
|
|
||
| aliasTags, parseErr := structtag.Parse(string(fields[1].Tag)) | ||
| require.NoError(t, parseErr) | ||
|
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| for k, v := range tbl.expectedAlias { | ||
| val, err := aliasTags.Get(k) | ||
| require.NoError(t, err) | ||
| assert.Equal(t, v, val.Name) | ||
| } | ||
| assert.Equal(t, len(tbl.expectedAlias), aliasTags.Len()) | ||
|
|
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| // for _, f := range fields { | ||
| // t.Logf("name: %s tag: %s", f.Name, string(f.Tag)) | ||
| // } | ||
| }) | ||
| } | ||
| } | ||
|
|
||
| func TestAliasManglerUnmangle(t *testing.T) { | ||
| sf := reflect.StructField{ | ||
| Name: "Foo", | ||
| Type: reflect.TypeOf(""), | ||
| } | ||
|
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| num := 42 | ||
| var nilInt *int | ||
|
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| aliasMangler := &AliasMangler{} | ||
|
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| originalSet := []FieldValueTuple{ | ||
| { | ||
| Field: sf, | ||
| Value: reflect.ValueOf(&num), | ||
| }, | ||
| { | ||
| Field: sf, | ||
| Value: reflect.ValueOf(nilInt), | ||
| }, | ||
| } | ||
|
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| val, err := aliasMangler.Unmangle(sf, originalSet) | ||
| require.NoError(t, err) | ||
|
|
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| assert.Equal(t, 42, val.Elem().Interface()) | ||
|
|
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| aliasSet := []FieldValueTuple{ | ||
| { | ||
| Field: sf, | ||
| Value: reflect.ValueOf(nilInt), | ||
| }, | ||
| { | ||
| Field: sf, | ||
| Value: reflect.ValueOf(&num), | ||
| }, | ||
| } | ||
|
|
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| val, err = aliasMangler.Unmangle(sf, aliasSet) | ||
| require.NoError(t, err) | ||
|
|
||
| assert.Equal(t, 42, val.Elem().Interface()) | ||
|
|
||
| bothSet := []FieldValueTuple{ | ||
| { | ||
| Field: sf, | ||
| Value: reflect.ValueOf(&num), | ||
| }, | ||
| { | ||
| Field: sf, | ||
| Value: reflect.ValueOf(&num), | ||
| }, | ||
| } | ||
|
|
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| _, err = aliasMangler.Unmangle(sf, bothSet) | ||
| assert.NotNil(t, err) // there should be an error if both are set! | ||
|
|
||
| neitherSet := []FieldValueTuple{ | ||
| { | ||
| Field: sf, | ||
| Value: reflect.ValueOf(nilInt), | ||
| }, | ||
| { | ||
| Field: sf, | ||
| Value: reflect.ValueOf(nilInt), | ||
| }, | ||
| } | ||
|
|
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| val, err = aliasMangler.Unmangle(sf, neitherSet) | ||
| require.NoError(t, err) | ||
|
|
||
| assert.True(t, val.IsNil()) | ||
|
|
||
| } |