116 lines
5.0 KiB
Markdown
116 lines
5.0 KiB
Markdown
# config
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Thread-safe configuration from TOML files, environment variables, command-line
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arguments and registered defaults. Requires Go 1.27.1. The only runtime dependency
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is [lixenwraith/toml](https://github.com/lixenwraith/toml).
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```go
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package main
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import (
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"log"
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"time"
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"github.com/lixenwraith/config"
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)
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type Settings struct {
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Port uint16 `toml:"port"`
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Timeout time.Duration `toml:"timeout"`
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}
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func main() {
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initial := Settings{Port: 8080, Timeout: 5 * time.Second}
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cfg, err := config.NewBuilder().
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WithTarget(&initial).
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WithFile("config.toml").
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WithEnvPrefix("APP_").
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WithArgs([]string{"--port=9090"}).
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Build()
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if err != nil { log.Fatal(err) }
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latest, err := cfg.AsStruct()
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if err != nil { log.Fatal(err) }
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log.Printf("%+v", latest.(*Settings))
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}
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```
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```toml
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# Service settings
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timeout = "10s"
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port = 8080
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```
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Precedence is CLI > environment > file > default. Register paths with `Register`
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or structs with `RegisterStruct`; defaults define the types used to validate new
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values. `LoadFile`, `LoadEnv` and `LoadCLI` replace their complete source. A failed
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source load keeps its previous values. Removing an environment variable, CLI flag
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or file key removes the old override on the next load.
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`Get` returns a detached raw source value: environment and CLI values remain
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strings, TOML integers are int64. `GetTyped[T]`, `Scan`, `ScanSource`, `ScanTyped[T]`
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and `ScanMap` provide checked conversions. Errors leave destinations unchanged;
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missing struct fields retain their existing values. `AsStruct` returns a detached
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snapshot on every call. Build fills `WithTarget` once; subsequent reloads never
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mutate that caller-owned object.
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## Migration
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- Only TOML files and `toml` tags are supported. JSON/YAML parsers, format constants
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and alternate tag modes are removed. Existing format/tag option methods accept
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only `toml` (`auto` remains an alias for TOML for file options).
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- Numeric conversion rejects overflow, negative unsigned inputs, fractional
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integer conversion, non-finite floats and integer-to-float precision loss.
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Float64-to-float32 rounding within range remains supported. Full uint64 is
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supported in memory; saving a value above MaxInt64 fails without changing the
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destination file. Use an application-level string representation if needed.
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- Strings can represent decimal numbers, booleans, durations, RFC3339
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timestamps, IP addresses, CIDR networks and URLs. For a slice or array path,
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environment and command-line text splits at commas; a string from a file,
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`Set` or `ScanMap` is one element, since those have native arrays and a pattern
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may hold a comma. Boolean to string conversion uses `true`/`false`.
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Conversion errors name the path, never the value. There are no user decode hooks or automatic
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`encoding.TextUnmarshaler` calls.
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- Setters and source loads reject values incompatible with registered defaults
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immediately. Check their errors. Untyped nil defaults leave the value type open;
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typed nil pointers retain their declared type. Unsupported values, non-finite
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floats and cyclic/deep graphs are rejected. Configuration value depth is 128.
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- All public values, defaults, options and clones own their mutable containers.
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Existing references returned from `AsStruct` are snapshots, not live objects.
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- Saves standardize formatting and retain loaded comments as a preamble. Comment
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positions are not preserved. Existing file permissions are retained; new files
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use 0600. Only registered paths are saved, so unknown file keys are omitted.
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- Paths use dot-separated ASCII key segments. Numeric-only segments and overlapping
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registrations such as `server` plus `server.port` are rejected. Embedded fields
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are not promoted. Recursive struct schemas are unsupported.
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## Watching
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```go
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changes := cfg.WatchWithOptions(config.DefaultWatchOptions())
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defer cfg.StopAutoUpdate()
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for event := range changes {
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// Events are hints; always read the latest complete state.
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log.Print(event)
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latest, err := cfg.AsStruct()
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if err != nil { log.Print(err); continue }
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_ = latest.(*Settings)
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}
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```
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The watcher fingerprints file contents, waits for a quiet debounce interval, then
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validates and publishes. Invalid edits, timeouts, deletion and a permission
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change, reported once before the next edit applies, retain the last valid state. Cancelled, expired or superseded reloads
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cannot publish. Stop closes subscriptions synchronously; a new Watch call can
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restart watching. Notifications are buffered and best effort.
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## Documentation
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- [Quick start](doc/quick-start.md), [builder](doc/builder.md), [access](doc/access.md)
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- [Files and saving](doc/file.md), [environment](doc/env.md), [CLI](doc/cli.md)
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- [Live reconfiguration](doc/reconfiguration.md), [validation](doc/validator.md)
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- [Architecture](doc/architecture.md), [audit evidence](doc/audit.md)
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Run `go test -race ./...` and `go vet ./...`. CI also executes the 386 suite,
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cross-compiles for Windows and runs bounded numeric conversion fuzzing.
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BSD-3-Clause; see LICENSE.
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