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feat: initial CLI for codegen with support for golang strongly typed accessors (#13)
<!-- Please use this template for your pull request. --> <!-- Please use the sections that you need and delete other sections --> ## This PR adds initial CLI for codegen with support for golang strongly typed accessors ### Related Issues https://github.com/orgs/open-feature/projects/17?pane=issue&itemId=74282748 ### Follow-up Tasks split to support additional languages add unit tests --------- Signed-off-by: Florin-Mihai Anghel <[email protected]>
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‎.gitignore‎

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# If you prefer the allow list template instead of the deny list, see community template:
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# https://github.com/github/gitignore/blob/main/community/Golang/Go.AllowList.gitignore
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#
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# Binaries for programs and plugins
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*.exe
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*.exe~
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*.dll
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*.so
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*.dylib
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# Test binary, built with `go test -c`
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*.test
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# Output of the go coverage tool, specifically when used with LiteIDE
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*.out
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# Dependency directories (remove the comment below to include it)
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# vendor/
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# Go workspace file
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go.work
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go.work.sum
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# env file
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.env

‎src/example_go/experimentflags.go‎

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package experimentflags
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import (
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"codegen/providers"
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"context"
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"github.com/open-feature/go-sdk/openfeature"
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)
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var client *openfeature.Client = nil
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// This is a flag.
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var MyOpenFeatureFlag = struct {
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Value providers.BooleanProvider
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}{
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Value: func(ctx context.Context) (bool, error) {
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return client.BooleanValue(ctx, "myOpenFeatureFlag", false, openfeature.EvaluationContext{})
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},
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}
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func init() {
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client = openfeature.NewClient("experimentflags")
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}

‎src/generators/generator.go‎

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package generator
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import (
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"bytes"
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"fmt"
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"os"
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"text/template"
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)
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// FlagType are the primitive types of flags.
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type FlagType int
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// Collection of the different kinds of flag types
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const (
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UnknownFlagType FlagType = iota
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IntType
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FloatType
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BoolType
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StringType
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ObjectType
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)
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// FlagTmplData is the per-flag specific data.
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// It represents a common interface between Mendel source and codegen file output.
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type FlagTmplData struct {
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Name string
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Type FlagType
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DefaultValue string
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Docs string
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}
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// BaseTmplData is the base for all OpenFeature code generation.
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type BaseTmplData struct {
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OutputDir string
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Flags []*FlagTmplData
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}
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type TmplDataInterface interface {
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// BaseTmplDataInfo returns a pointer to a BaseTmplData struct containing
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// all the relevant information needed for metadata construction.
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BaseTmplDataInfo() *BaseTmplData
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}
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type Input struct {
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BaseData *BaseTmplData
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}
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// Generator provides interface to generate language specific, strongly-typed flag accessors.
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type Generator interface {
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Generate(input Input) error
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SupportedFlagTypes() map[FlagType]bool
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}
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// GenerateFile receives data for the Go template engine and outputs the contents to the file.
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func GenerateFile(funcs template.FuncMap, outputPath string, contents string, data TmplDataInterface) error {
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contentsTmpl, err := template.New("contents").Funcs(funcs).Parse(contents)
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if err != nil {
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return fmt.Errorf("error initializing template: %v", err)
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}
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var buf bytes.Buffer
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if err := contentsTmpl.Execute(&buf, data); err != nil {
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return fmt.Errorf("error executing template: %v", err)
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}
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f, err := os.Create(outputPath)
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if err != nil {
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return fmt.Errorf("error creating file %q: %v", outputPath, err)
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}
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defer f.Close()
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writtenBytes, err := f.Write(buf.Bytes())
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if err != nil {
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return fmt.Errorf("error writing contents to file %q: %v", outputPath, err)
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}
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if writtenBytes != buf.Len() {
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return fmt.Errorf("error writing entire file %v: writtenBytes != expectedWrittenBytes", outputPath)
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}
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return nil
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}

‎src/generators/golang/golang.go‎

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package golang
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import (
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generator "codegen/generators"
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_ "embed"
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"sort"
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"strconv"
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"text/template"
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"github.com/iancoleman/strcase"
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)
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// TmplData contains the Golang-specific data and the base data for the codegen.
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type TmplData struct {
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*generator.BaseTmplData
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GoPackage string
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}
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type genImpl struct {
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file string
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goPackage string
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}
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// BaseTmplDataInfo provides the base template data for the codegen.
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func (td *TmplData) BaseTmplDataInfo() *generator.BaseTmplData {
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return td.BaseTmplData
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}
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// supportedFlagTypes is the flag types supported by the Go template.
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var supportedFlagTypes = map[generator.FlagType]bool{
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generator.FloatType: true,
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generator.StringType: true,
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generator.IntType: true,
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generator.BoolType: true,
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generator.ObjectType: false,
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}
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func (*genImpl) SupportedFlagTypes() map[generator.FlagType]bool {
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return supportedFlagTypes
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}
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//go:embed golang.tmpl
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var golangTmpl string
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// Go Funcs BEGIN
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func flagVarName(flagName string) string {
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return strcase.ToCamel(flagName)
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}
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func flagInitParam(flagName string) string {
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return strconv.Quote(flagName)
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}
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// flagVarType returns the Go type for a flag's proto definition.
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func providerType(t generator.FlagType) string {
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switch t {
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case generator.IntType:
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return "IntProvider"
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case generator.FloatType:
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return "FloatProvider"
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case generator.BoolType:
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return "BooleanProvider"
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case generator.StringType:
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return "StringProvider"
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}
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return ""
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}
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func flagAccessFunc(t generator.FlagType) string {
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switch t {
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case generator.IntType:
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return "IntValue"
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case generator.FloatType:
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return "FloatValue"
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case generator.BoolType:
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return "BooleanValue"
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case generator.StringType:
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return "StringValue"
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}
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return ""
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}
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func supportImports(flags []*generator.FlagTmplData) []string {
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var res []string
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if len(flags) > 0 {
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res = append(res, "\"context\"")
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res = append(res, "\"github.com/open-feature/go-sdk/openfeature\"")
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res = append(res, "\"codegen/providers\"")
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}
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sort.Strings(res)
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return res
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}
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func defaultValueLiteral(flag *generator.FlagTmplData) string {
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switch flag.Type {
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case generator.StringType:
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return strconv.Quote(flag.DefaultValue)
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default:
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return flag.DefaultValue
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}
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}
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func typeString(flagType generator.FlagType) string {
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switch flagType {
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case generator.StringType:
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return "string"
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case generator.IntType:
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return "int"
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case generator.BoolType:
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return "bool"
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case generator.FloatType:
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return "float64"
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default:
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return ""
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}
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}
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// Go Funcs END
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// Generate generates the Go flag accessors for OpenFeature.
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func (g *genImpl) Generate(input generator.Input) error {
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funcs := template.FuncMap{
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"FlagVarName": flagVarName,
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"FlagInitParam": flagInitParam,
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"ProviderType": providerType,
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"FlagAccessFunc": flagAccessFunc,
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"SupportImports": supportImports,
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"DefaultValueLiteral": defaultValueLiteral,
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"TypeString": typeString,
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}
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td := TmplData{
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BaseTmplData: input.BaseData,
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GoPackage: g.goPackage,
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}
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return generator.GenerateFile(funcs, g.file, golangTmpl, &td)
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}
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// Params are parameters for creating a Generator
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type Params struct {
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File string
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GoPackage string
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}
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// NewGenerator creates a generator for Go.
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func NewGenerator(params Params) generator.Generator {
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return &genImpl{
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file: params.File,
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goPackage: params.GoPackage,
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}
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}

‎src/generators/golang/golang.tmpl‎

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package {{.GoPackage}}
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import (
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{{- range $_, $p := SupportImports .Flags}}
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{{$p}}
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{{- end}}
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)
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var client *openfeature.Client = nil
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{{- range .Flags}}
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// {{.Docs}}
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var {{FlagVarName .Name}} = struct {
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Value providers.{{ProviderType .Type}}
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}{
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Value: func(ctx context.Context) ({{TypeString .Type}}, error) {
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return client.{{FlagAccessFunc .Type}}(ctx, {{FlagInitParam .Name}}, {{DefaultValueLiteral .}}, openfeature.EvaluationContext{})
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},
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}
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{{- end}}
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func init() {
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client = openfeature.NewClient("{{.GoPackage}}")
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}

‎src/go.mod‎

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module codegen
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go 1.22.5
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require (
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github.com/go-logr/logr v1.4.2 // indirect
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golang.org/x/exp v0.0.0-20240506185415-9bf2ced13842 // indirect
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)
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require (
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github.com/iancoleman/strcase v0.3.0
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github.com/open-feature/go-sdk v1.12.0
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github.com/santhosh-tekuri/jsonschema/v5 v5.3.1
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)

‎src/go.sum‎

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github.com/go-logr/logr v1.4.2 h1:6pFjapn8bFcIbiKo3XT4j/BhANplGihG6tvd+8rYgrY=
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github.com/go-logr/logr v1.4.2/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
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github.com/iancoleman/strcase v0.3.0 h1:nTXanmYxhfFAMjZL34Ov6gkzEsSJZ5DbhxWjvSASxEI=
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github.com/iancoleman/strcase v0.3.0/go.mod h1:iwCmte+B7n89clKwxIoIXy/HfoL7AsD47ZCWhYzw7ho=
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github.com/open-feature/go-sdk v1.12.0 h1:V0MAG3lC9o7Pmq0gxlqtKpoasDTm3to9vuvZKyUhhPk=
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github.com/open-feature/go-sdk v1.12.0/go.mod h1:UDNuwVrwY5FRHIluVRYzvxuS3nBkhjE6o4tlwFuHxiI=
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github.com/santhosh-tekuri/jsonschema/v5 v5.3.1 h1:lZUw3E0/J3roVtGQ+SCrUrg3ON6NgVqpn3+iol9aGu4=
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github.com/santhosh-tekuri/jsonschema/v5 v5.3.1/go.mod h1:uToXkOrWAZ6/Oc07xWQrPOhJotwFIyu2bBVN41fcDUY=
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golang.org/x/exp v0.0.0-20240506185415-9bf2ced13842 h1:vr/HnozRka3pE4EsMEg1lgkXJkTFJCVUX+S/ZT6wYzM=
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golang.org/x/exp v0.0.0-20240506185415-9bf2ced13842/go.mod h1:XtvwrStGgqGPLc4cjQfWqZHG1YFdYs6swckp8vpsjnc=
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golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c h1:qgOY6WgZOaTkIIMiVjBQcw93ERBE4m30iBm00nkL0i8=
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golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
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golang.org/x/text v0.15.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
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rsc.io/quote v1.5.2 h1:w5fcysjrx7yqtD/aO+QwRjYZOKnaM9Uh2b40tElTs3Y=
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rsc.io/quote v1.5.2/go.mod h1:LzX7hefJvL54yjefDEDHNONDjII0t9xZLPXsUe+TKr0=
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rsc.io/sampler v1.3.0 h1:7uVkIFmeBqHfdjD+gZwtXXI+RODJ2Wc4O7MPEh/QiW4=
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rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=

‎src/input.json‎

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{
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"flags": {
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"myOpenFeatureFlag":{
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"flag_type": "boolean",
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"default_value": false,
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"description": "This is a flag."
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}
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}
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}

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