henry3260 opened a new pull request, #75602:
URL: https://github.com/apache/airflow/pull/75602
`actx.DagRun()` now carries the conf the Dag run was triggered with, and
reads it into a struct with typed fields.
```go
type etlConf struct {
TargetTable string
Limit int
Since time.Time
}
func load(actx airflow.Context) error {
etl := etlConf{Limit: 100}
if err := actx.DagRun().UnmarshalConf(&etl); err != nil {
return err
}
...
}
```
For a run triggered with `{"target_table": "sales", "since":
"2024-01-31T00:00:00Z"}`, `etl.TargetTable` is `"sales"`, `etl.Since` is that
date, and `etl.Limit` stays `100`.
- The supervisor already sends the conf with the task's startup details, but
the runtime dropped it on the way to the task, so a Go task could not read what
its run was triggered with while a Python or a Java task can. `sdk.DagRun.Conf`
is the conf as a `map[string]any`, and is nil for a run triggered without one.
- Reading that map costs an assertion per key, and an integer has no single
type to assert, because the wire picks its width from the value.
`UnmarshalConf` leaves the types to the task author instead.
- A key reaches the field whose name folds to the same token once case and
underscores are ignored, which is how a TaskFlow argument already reaches its
field, so `target_table` reaches `TargetTable`. A `json:` tag renames the field
and matches the same way. Objects nested in the conf follow the same rule,
including objects in slices and objects that are map values; the keys of a map
field stay as written.
- Keys that match no field are ignored, because other tasks in the run may
read them. A field with no matching key keeps the value the struct already
holds, so defaults are set before the call.
- It returns an error when a value does not fit the type of its field, when
two keys match one field and neither names it exactly, or when two fields of
the struct differ only in case or underscores.
related: #74674 — that PR exposes `Conf` together with `RunType` and
`RunAfter`. The first commit here overlaps it, and I will drop that commit and
rebase on it if it lands first. The typed binding is the part neither it nor
the Java SDK's #75542 covers.
The Java SDK is getting the same feature in #75542, and the TS SDK the conf
itself in #75563. The matching rules here follow #75542 so that a conf key
reaches the same field in every SDK.
Verified in `go-sdk/`: `go test ./...`, `go test -race ./...`, `go vet
./...`, the prek pre-commit and manual stages, and `breeze build-docs
apache-airflow`. `TestTriggerDagRunRejectsAnInvalidSpec` fails on my machine
with and without this change, because a Go 1.27 toolchain prints a different
`encoding/json` error string than the repository's Go 1.25 target; it is
unrelated to this PR.
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