[henry3260]

Why

A Go task reads the Dag run conf from actx.DagRun().Conf, which is a map[string]any. Every key therefore costs a type assertion, and a wrong one fails as a panic or as a silent zero value rather than as an error the task can report. A task that reads several keys carries a block of assertions in front of the work it actually does.

Reading the conf into a struct puts the types where the task author declares them, but the names do not line up on their own: a conf key is written target_table where the Go field has to be TargetTable, and encoding/json matches a key to a field only when the two differ at most in case. Folding case and underscores is how a TaskFlow argument already reaches an untagged field, so a conf key can reach its field by the same folding.

The Java SDK already offers this as context.dagRun.getConf(type), with the same folding rule (see airflow-core/docs/authoring-and-scheduling/language-sdks/java.rst). This gives the Go SDK the equivalent.

related: #74674 — that PR exposed Conf itself and has merged; this one adds the typed read on top of it, which is the split agreed in review.

What

• go-sdk/sdk/conf.go (new) adds DagRun.UnmarshalConf(target any). It renames each conf key to the name of the field that key matches, then decodes the result with encoding/json:

  • a key reaches the field whose name matches it once case and underscores are ignored, and a key that names a field exactly wins over one that only folds onto it;
  • a json: tag renames the field and matches the same way, and json:"-" takes no key — including on an embedded struct, whose fields encoding/json also skips;
  • objects nested in the conf follow the same rule, including objects in slices, arrays and map values, while the keys of a map field stay as written, because they are data rather than field names;
  • a type that decodes itself, such as time.Time, is left alone;
  • a key that matches no field is ignored, because another task in the run may read it, so a field with no matching key keeps the value the target already holds and defaults can be 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, and when two fields of a struct differ only in case or underscores.

  Field indexes are cached per struct type in a sync.Map, so a conf holding a list of many objects indexes each struct once.

• A number that lands in a field of type any, or in the values of a map[string]any or []any field, is decoded as a json.Number rather than a float64, since a float64 cannot hold every integer a conf carries — an id above 2^53 would otherwise reach the task with its last digits changed and no error to show for it. The task reads the exact value through Int64 or Float64; a field with a Go number type is unaffected.

• go-sdk/sdk/context.go points the Conf doc comment at UnmarshalConf.

• airflow-core/docs/authoring-and-scheduling/language-sdks/go.rst adds a "Reading the Dag run conf" section with those rules and links to it from the existing Conf paragraph.

• go-sdk/sdk/conf_test.go (new) covers the matching rules, nested objects, json: tags, promoted and shadowed fields, the skipped embedded struct, the json.Number decoding above, a run triggered without a conf, and each error case.

go test ./... and go test -race ./... pass in go-sdk, and breeze build-docs apache-airflow task-sdk builds the new docs section.

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[jason810496]

Nice, thanks for the PR to fill up the gap.
IIUC, this PR will only focus on the UnmarshalConf and #74674 will focus on exposing the conf attribute directly right?

[henry3260]

Nice, thanks for the PR to fill up the gap. IIUC, this PR will only focus on the UnmarshalConf and #74674 will focus on exposing the conf attribute directly right?

Yes, I’ll wait until #74674 is merged

[jason810496]

I just merged #74674 btw, please feel free to ping me when this PR is ready.

[henry3260]

cc @jason810496

[jason810496]

Thanks for the update.

[henry3260]

Thanks All commets are addressed

[jason810496]

Thanks for the update.