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Configloader strict mode (and refactoring) (#114)
* Improve type testing * Add more handlers * Big refactor * Fix linter errors * Improve documentation * Improve documentation * Improve errors * Move the options to own file * Fix embedding * Fix the env / name tags * Add env tests * Fix tests * Fix linter * Make env default
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,64 @@ | ||
| package configloader | ||
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| import ( | ||
| "fmt" | ||
| "reflect" | ||
| "strings" | ||
| ) | ||
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| // ConfigLoadError represents the errors that occurred during config loading. | ||
| type ConfigLoadError struct { | ||
| Value reflect.Type | ||
| Errors []error | ||
| } | ||
|
|
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| func (e *ConfigLoadError) Add(err error) { | ||
| if err != nil { | ||
| e.Errors = append(e.Errors, err) | ||
| } | ||
| } | ||
|
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| func (e *ConfigLoadError) Error() string { | ||
| var msgs = make([]string, len(e.Errors)) | ||
| for i, err := range e.Errors { | ||
| msgs[i] = err.Error() | ||
| } | ||
| return fmt.Sprintf("failed to load %s:\n%s", e.Value.String(), | ||
| strings.Join(msgs, "\n")) | ||
| } | ||
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| func (e *ConfigLoadError) Unwrap() []error { | ||
| return e.Errors | ||
| } | ||
|
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| // FieldError represents an error that occurred while processing a specific field. | ||
| type FieldError struct { | ||
| Field | ||
| Err error | ||
| } | ||
|
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| func (e FieldError) Error() string { | ||
| return fmt.Sprintf("error processing field %s: %v", e.Field.String(), e.Err) | ||
| } | ||
|
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| func (e FieldError) Unwrap() error { | ||
| return e.Err | ||
| } | ||
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| // MissingEnvError represents an error when a required environment variable is not found. | ||
| type MissingEnvError struct { | ||
| Key string | ||
| } | ||
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| func (e MissingEnvError) Error() string { | ||
| return fmt.Sprintf("environment variable %s not found", e.Key) | ||
| } | ||
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| // UnsupportedTypeError represents an error when trying to process a field with an unsupported type. | ||
| type UnsupportedTypeError struct { | ||
| Type reflect.Type | ||
| } | ||
|
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| func (e UnsupportedTypeError) Error() string { | ||
| return fmt.Sprintf("unsupported type %v", e.Type) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,121 @@ | ||
| package configloader | ||
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| import "reflect" | ||
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| type Option func(*Loader) | ||
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| // WithTypeHandler registers a custom type conversion function for a specific type T. | ||
| // The function should convert a string environment value to type T, returning an error | ||
| // if the conversion fails. | ||
| // | ||
| // Example: | ||
| // | ||
| // configloader.Load(&cfg, WithTypeHandler(func(s string) (time.Duration, error) { | ||
| // return time.ParseDuration(s) | ||
| // })) | ||
| func WithTypeHandler[T any](f func(string) (T, error)) Option { | ||
| return func(l *Loader) { | ||
| var zero T | ||
| l.handlers[reflect.TypeOf(zero)] = func(value string) (any, error) { | ||
| return f(value) | ||
| } | ||
| } | ||
| } | ||
|
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| // WithNameTag sets the struct tag used to override a field's name in the environment variable path. | ||
| // The tag value replaces just the field's name segment while still following the normal path construction | ||
| // rules (prefix + path + name). | ||
| // | ||
| // Example with WithNameTag("name"): | ||
| // | ||
| // type Config struct { | ||
| // Database struct { | ||
| // Host string `name:"HOSTNAME"` // Looks for DATABASE_HOSTNAME | ||
| // } | ||
| // } | ||
| // configloader.Load(&cfg) | ||
| // | ||
| // Example with both prefix and name tag: | ||
| // | ||
| // type Config struct { | ||
| // Database struct { | ||
| // Host string `name:"HOSTNAME"` // Looks for APP_DATABASE_HOSTNAME | ||
| // } | ||
| // } | ||
| // configloader.Load(&cfg, WithPrefix("APP")) | ||
| func WithNameTag(tag string) Option { | ||
| return func(l *Loader) { | ||
| l.nameTag = tag | ||
| } | ||
| } | ||
|
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| // WithEnvTag sets the struct tag used to completely override the environment variable name for a field. | ||
| // When a field has this tag, its value is used as-is for the environment variable name, bypassing all | ||
| // other name construction rules including prefixes and path building. | ||
| // | ||
| // Example with WithEnvTag("env"): | ||
| // | ||
| // type Config struct { | ||
| // Database struct { | ||
| // // Despite nesting, looks directly for "DB_HOST" | ||
| // Host string `env:"DB_HOST"` | ||
| // } | ||
| // } | ||
| // configloader.Load(&cfg) | ||
| // | ||
| // Example showing prefix is ignored with env tag: | ||
| // | ||
| // type Config struct { | ||
| // Database struct { | ||
| // // Still only looks for "DB_HOST", prefix is not applied | ||
| // Host string `env:"DB_HOST"` | ||
| // } | ||
| // } | ||
| // configloader.Load(&cfg, WithPrefix("APP")) | ||
| func WithEnvTag(tag string) Option { | ||
| return func(l *Loader) { | ||
| l.envTag = tag | ||
| } | ||
| } | ||
|
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| // WithDefaultTag sets the struct tag used for specifying default values. | ||
| // If an environment variable is not found, the value of this tag will be used instead. | ||
| // | ||
| // Example: | ||
| // | ||
| // type Config struct { | ||
| // Port int `default:"8080"` // Will use 8080 if PORT is not set | ||
| // } | ||
| // configloader.Load(&cfg, WithDefaultTag("default")) | ||
| func WithDefaultTag(tag string) Option { | ||
| return func(l *Loader) { | ||
| l.defaultTag = tag | ||
| } | ||
| } | ||
|
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| // WithPrefix sets a prefix that will be prepended to all environment variable names. | ||
| // The prefix and field name will be joined with an underscore. | ||
| // | ||
| // Example: | ||
| // | ||
| // type Config struct { | ||
| // Port int // Will look for "APP_PORT" environment variable | ||
| // } | ||
| // configloader.Load(&cfg, WithPrefix("APP")) | ||
| func WithPrefix(prefix string) Option { | ||
| return func(l *Loader) { | ||
| l.prefix = prefix | ||
| } | ||
| } | ||
|
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| // WithEnv sets a custom function for looking up environment variables. | ||
| // This is primarily useful for testing or when environment variables need to be | ||
| // sourced from somewhere other than os.LookupEnv. | ||
| // | ||
| // The function should return the value and a boolean indicating whether the variable | ||
| // was found, similar to os.LookupEnv. | ||
| func WithEnv(env func(string) (string, bool)) Option { | ||
| return func(l *Loader) { | ||
| l.env = env | ||
| } | ||
| } |
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