refactor[next]: cleaner toolchain

docs/user/next/advanced/HackTheToolchain.md

@@ -0,0 +1,129 @@
+```python
+import dataclasses
+import typing
+
+from gt4py import next as gtx
+from gt4py.next.otf import workflow
+from gt4py import eve
+```
+
+<link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet"><script src="https://spcl.github.io/dace/webclient2/dist/sdfv.js"></script>
+<link href="https://spcl.github.io/dace/webclient2/sdfv.css" rel="stylesheet">
+
+## Replace Steps
+
+```python
+cached_lowering_toolchain = gtx.backend.DEFAULT_PROG_TRANSFORMS.replace(
+    past_to_itir=workflow.CachedStep(
+        step=gtx.ffront.past_to_itir.PastToItirFactory(),
+        hash_function=eve.utils.content_hash
+    )
+)
+```
+
+## Skip Steps / Change Order
+
+```python
+gtx.backend.DEFAULT_PROG_TRANSFORMS.step_order
+```
+
+    ['func_to_past',
+     'past_lint',
+     'past_inject_args',
+     'past_transform_args',
+     'past_to_itir']
+
+```python
+@dataclasses.dataclass(frozen=True)
+class SkipLinting(gtx.backend.ProgramTransformWorkflow):
+    @property
+    def step_order(self):
+        return [
+            "func_to_past",
+            # not running "past_lint"
+            "past_inject_args",
+            "past_transform_args",
+            "past_to_itir",
+        ]
+
+same_steps = dataclasses.asdict(gtx.backend.DEFAULT_PROG_TRANSFORMS)
+skip_linting_transforms = SkipLinting(
+    **same_steps
+)
+```
+
+## Alternative Factory
+
+```python
+class MyCodeGen:
+    ...
+
+class Cpp2BindingsGen:
+    ...
+
+class PureCpp2WorkflowFactory(gtx.program_processors.runners.gtfn.GTFNCompileWorkflowFactory):
+    translation: workflow.Workflow[
+        gtx.otf.stages.ProgramCall, gtx.otf.stages.ProgramSource]  = MyCodeGen()
+    bindings: workflow.Workflow[
+        gtx.otf.stages.ProgramSource, gtx.otf.stages.CompilableSource] = Cpp2BindingsGen()
+
+PureCpp2WorkflowFactory(cmake_build_type=gtx.config.CMAKE_BUILD_TYPE.DEBUG)
+```
+
+## Invent new Workflow Types
+
+````mermaid
+graph LR
+
+IN_T --> i{{split}} --> A_T --> a{{track_a}} --> B_T --> o{{combine}} --> OUT_T
+i --> X_T --> x{{track_x}} --> Y_T --> o
+
+
+```python
+IN_T = typing.TypeVar("IN_T")
+A_T = typing.TypeVar("A_T")
+B_T = typing.TypeVar("B_T")
+X_T = typing.TypeVar("X_T")
+Y_T = typing.TypeVar("Y_T")
+OUT_T = typing.TypeVar("OUT_T")
+
+@dataclasses.dataclass(frozen=True)
+class FullyModularDiamond(
+    workflow.ChainableWorkflowMixin[IN_T, OUT_T],
+    workflow.ReplaceEnabledWorkflowMixin[IN_T, OUT_T],
+    typing.Protocol[IN_T, OUT_T, A_T, B_T, X_T, Y_T]
+):
+    split: workflow.Workflow[IN_T, tuple[A_T, X_T]]
+    track_a: workflow.Workflow[A_T, B_T]
+    track_x: workflow.Workflow[X_T, Y_T]
+    combine: workflow.Workflow[tuple[B_T, Y_T], OUT_T]
+
+    def __call__(self, inp: IN_T) -> OUT_T:
+        a, x = self.split(inp)
+        b = self.track_a(a)
+        y = self.track_x(x)
+        return self.combine((b, y))
+
+
+@dataclasses.dataclass(frozen=True)
+class PartiallyModularDiamond(
+    workflow.ChainableWorkflowMixin[IN_T, OUT_T],
+    workflow.ReplaceEnabledWorkflowMixin[IN_T, OUT_T],
+    typing.Protocol[IN_T, OUT_T, A_T, B_T, X_T, Y_T]
+):
+    track_a: workflow.Workflow[A_T, B_T]
+    track_x: workflow.Workflow[X_T, Y_T]
+
+    def split(inp: IN_T) -> tuple[A_T, X_T]:
+        ...
+
+    def combine(b: B_T, y: Y_T) -> OUT_T:
+        ...
+
+    def __call__(inp: IN_T) -> OUT_T:
+        a, x = self.split(inp)
+        return self.combine(
+            b=self.track_a(a),
+            y=self.track_x(x)
+        )
+````