Jason(Zhe-You) Liu c3043c266c Java SDK: Choose one of several tasks with a branch (#74439) ...

* Java SDK: Choose one of several tasks with a branch

A condition picks between two tasks, but a Dag that routes work by size or
by region needs more than two, and splitting that into nested conditions
makes the graph unreadable.

`DagDef.Branch` and `@Builder.Branch` declare a task that chooses one of
the tasks listed with `option(...)`; every other one is skipped. 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`.

Each authoring style names the case in the way that style can type-check. A
`BranchTask` returns the case's own class, so javac checks it; two cases
that share a class are rejected where the second is named, since the branch
could not tell them apart. A `@Builder.Branch` method has no such class to
name -- a task method's implementation is generated -- so it returns a
`TaskId` from the generated `<Dag>Builder.TaskIds`, which holds one
constant per task of the Dag. Either way nothing hard-codes a task id
string, and the generated holder is emitted only for a Dag that declares a
branch.

* Java SDK: Name the multi-way branch Switch, as the other SDKs do

* Java SDK: Name a switch case by its task class in both styles

* Java SDK: Say when a switch rejects a choice and when it fails

* Java SDK: Cover a generated switch that names a task it cannot choose

* Java SDK: Check a switch carries the chosen task's id

* Java SDK: Let a wiring view name a switch's cases in more than one call

2026-10-09 14:30:52 +08:00

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src

Java SDK: Choose one of several tasks with a branch (#74439)

2026-10-09 14:30:52 +08:00

build.gradle.kts

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