Better error messages

.pre-commit-config.yaml

@@ -18,4 +18,5 @@ repos:
     rev: v1.9.0
     hooks:
       - id: mypy
-        args: [--strict, --ignore-missing-imports]
+        args: [--strict, --install-types, --non-interactive]
+        additional_dependencies: [sympy, attrs, pytest, click, dask]

example/extra.py

@@ -7,26 +7,31 @@
 
 JUMP: int = 10
 
+
 @task()
 def increase(num: int) -> int:
     """Add globally-configured integer JUMP to a number."""
     return num + JUMP
 
+
 @task()
 def increment(num: int) -> int:
     """Increment an integer."""
     return num + 1
 
+
 @task()
 def double(num: int) -> int:
     """Double an integer."""
     return 2 * num
 
+
 @task()
 def mod10(num: int) -> int:
     """Calculate supplied integer modulo 10."""
     return num % 10
 
+
 @task()
 def sum(left: int, right: int) -> int:
     """Add two integers."""

example/workflow_complex.py

@@ -3,7 +3,7 @@
 Useful as an example of a workflow with a nested task.
 
 ```sh
-$ python -m dewret workflow_complex.py --pretty run
+$ python -m dewret workflow_complex.py --pretty nested_workflow
 ```
 """
 
@@ -12,12 +12,10 @@
 
 STARTING_NUMBER: int = 23
 
+
 @nested_task()
 def nested_workflow() -> int | float:
     """Creates a graph of task calls."""
     left = double(num=increase(num=STARTING_NUMBER))
     right = increase(num=increase(num=17))
-    return sum(
-        left=left,
-        right=right
-    )
+    return sum(left=left, right=right)

src/dewret/__main__.py

@@ -29,13 +29,28 @@
 from .renderers.cwl import render as cwl_render
 from .tasks import Backend, construct
 
+
 @click.command()
-@click.option("--pretty", is_flag=True, show_default=True, default=False, help="Pretty-print output where possible.")
-@click.option("--backend", type=click.Choice(list(Backend.__members__)), show_default=True, default=Backend.DASK.name, help="Backend to use for workflow evaluation.")
+@click.option(
+    "--pretty",
+    is_flag=True,
+    show_default=True,
+    default=False,
+    help="Pretty-print output where possible.",
+)
+@click.option(
+    "--backend",
+    type=click.Choice(list(Backend.__members__)),
+    show_default=True,
+    default=Backend.DASK.name,
+    help="Backend to use for workflow evaluation.",
+)
 @click.argument("workflow_py")
 @click.argument("task")
 @click.argument("arguments", nargs=-1)
-def render(workflow_py: str, task: str, arguments: list[str], pretty: bool, backend: Backend) -> None:
+def render(
+    workflow_py: str, task: str, arguments: list[str], pretty: bool, backend: Backend
+) -> None:
     """Render a workflow.
 
     WORKFLOW_PY is the Python file containing workflow.
@@ -49,14 +64,24 @@ def render(workflow_py: str, task: str, arguments: list[str], pretty: bool, back
     kwargs = {}
     for arg in arguments:
         if ":" not in arg:
-            raise RuntimeError("Arguments should be specified as key:val, where val is a JSON representation of the argument")
+            raise RuntimeError(
+                "Arguments should be specified as key:val, where val is a JSON representation of the argument"
+            )
         key, val = arg.split(":", 1)
         kwargs[key] = json.loads(val)
 
-    cwl = cwl_render(construct(task_fn(**kwargs), simplify_ids=True))
-    if pretty:
-        yaml.dump(cwl, sys.stdout, indent=2)
+    try:
+        cwl = cwl_render(construct(task_fn(**kwargs), simplify_ids=True))
+    except Exception as exc:
+        import traceback
+
+        print(exc, exc.__cause__, exc.__context__)
+        traceback.print_exc()
     else:
-        print(cwl)
+        if pretty:
+            yaml.dump(cwl, sys.stdout, indent=2)
+        else:
+            print(cwl)
+
 
 render()

src/dewret/backends/backend_dask.py

@@ -21,6 +21,7 @@
 from dewret.workflow import Workflow, Lazy, StepReference, Target
 from typing import Protocol, runtime_checkable, Any, cast
 
+
 @runtime_checkable
 class Delayed(Protocol):
     """Description of a dask `delayed`.
@@ -48,6 +49,7 @@ def compute(self, __workflow__: Workflow | None) -> StepReference[Any]:
         """
         ...
 
+
 def unwrap(task: Lazy) -> Target:
     """Unwraps a lazy-evaluated function to get the function.
 
@@ -69,6 +71,7 @@ def unwrap(task: Lazy) -> Target:
         raise RuntimeError("Task is not actually a callable")
     return cast(Target, task._obj)
 
+
 def is_lazy(task: Any) -> bool:
     """Checks if a task is really a lazy-evaluated function for this backend.
 
@@ -80,7 +83,10 @@ def is_lazy(task: Any) -> bool:
     """
     return isinstance(task, Delayed)
 
+
 lazy = delayed
+
+
 def run(workflow: Workflow | None, task: Lazy) -> StepReference[Any]:
     """Execute a task as the output of a workflow.
 
@@ -92,5 +98,7 @@ def run(workflow: Workflow | None, task: Lazy) -> StepReference[Any]:
     """
     # We need isinstance to reassure type-checker.
     if not isinstance(task, Delayed) or not is_lazy(task):
-        raise RuntimeError("Cannot mix backends")
+        raise RuntimeError(
+            f"{task} is not a dask delayed, perhaps you tried to mix backends?"
+        )
     return task.compute(__workflow__=workflow)