Documentation
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Overview ¶
Package main demonstrates file.DrainPatchAdapter and file.DrainPatchEncodedAdapter: ports.SinkPort-bound sink adapters that apply each stream item as a PARTIAL update to an existing typed file, instead of the whole-file overwrite file.DrainWriteFileAdapter performs.
Scenario: a service config file on disk receives a stream of incremental updates (e.g. from an admin API or config-management pipeline) and must be patched in place — untouched fields must survive.
Two scenes:
- DrainPatchAdapter: untyped map[string]any patches (JSON Merge Patch semantics via ports.File.Patch) — a SinkPort[map[string]any].
- DrainPatchEncodedAdapter: a typed patch struct via a dedicated patch codec (via ports.PatchEncoded) — a SinkPort[ConfigPatch]; fields in the patch codec but NOT in the file's own codec are still persisted.
Both adapters stay handle-first (a hand-built ports.File[T] passed directly, not declared via ports.FilePattern) because the patch item's type is deliberately different from the file's own whole-record type — the same reason file.ReadEachAdapter stays handle-first for its independent content type.
Run with: go run ./examples/file-patch-sink
Source Files