[jason810496]

• depends on: Java SDK: Pick one of two tasks with a condition #74438
• related: Java SDK: Pack each native Dag's source file into the bundle JAR #74096, Java SDK: Trigger another Dag's run from a native Java Dag #74440

Merge order:

1. Java SDK: Pack each native Dag's source file into the bundle JAR #74096 — Pack each native Dag's source file into the bundle JAR
2. Java SDK: Pick one of two tasks with a condition #74438 — Pick one of two tasks with a condition
3. Java SDK: Choose one of several tasks with a branch #74439 — Choose one of several tasks with a branch (current one)
4. Java SDK: Trigger another Dag's run from a native Java Dag #74440 — Trigger another Dag's run from a native Java Dag

Why

A condition picks between two tasks, but a Dag that routes work by size or by region needs more than two, and nesting conditions to get there makes the graph unreadable.

What changes

DagDef.Branch and @Builder.Branch declare a task that chooses one of the tasks listed with option(...); every other one is skipped. Neither style hard-codes a task id string.

// Interface style: the case is its own class, so javac checks the choice.
dag.Branch(PickPath.class).option(handleLong).option(handleShort);

public class PickPath implements BranchTask {
  @Override
  public Class<? extends Task> choose(Context context, Client client) {
    return ((Number) client.getXCom("extract")).longValue() > 1000
        ? HandleLong.class
        : HandleShort.class;
  }
}

// Annotation style: a task method's implementation is generated, so there is no class
// to name. The method returns a TaskId from the generated TaskIds instead.
@Builder.Branch(id = "pick_report")
public TaskId pickReport(long transformed) {
  return transformed > 100 ? EtlBuilder.TaskIds.REPORT_LONG : EtlBuilder.TaskIds.REPORT_SHORT;
}

@Builder.Deps
static class Wiring implements EtlDeps {
  void depends() {
    pickReport(transformed).option(reportLong()).option(reportShort());
  }
}

EtlBuilder.TaskIds holds one constant per task of the Dag and is generated only for a Dag that declares a branch.

• The chosen task's ID becomes the branch's return value, as it does for Python's branch operators.
• A branch chooses exactly one case, so a task that runs after several of them needs a trigger rule such as none_failed_min_one_success.
• Two cases that share a Task class are rejected where the second is named: a BranchTask could not tell them apart.
• The serialization conformance check now covers the shared switch Dag.

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Was generative AI tooling used to co-author this PR?

• Yes, with help of Claude Code Opus 5.5 following the guidelines

[jason810496]

Thanks for the review.