Merge pull request #161 from allenai/FromParamsDuJour

Some fixes for our favorite Tango component

CHANGELOG.md

@@ -29,6 +29,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `LocalWorkspace` now creates a symlink to the outputs of the latest run.
 - Tango is now better at guessing when a step has died and should be re-run.
 - Tango is now more lenient about registering the same class under the same name twice.
+- When you use `dict` instead of `Dict` in your type annotations, you now get a legible error message. Same for `List`, `Tuple`, and `Set`.
 
 ### Fixed
 
@@ -38,6 +39,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Made `FromParams` more efficient by only trying to parse the params as a `Step` when it looks like it actually could be a step.
 - Fixed bug where `Executor` would crash if `git` command could not be found.
 - Fixed bug where validation settings were not interpreted the right way by the torch trainer.
+- When you register the same name twice using `Registrable`, you get an error message. That error message now contains the correct class name.
 
 
 ## [v0.4.0](https://github.com/allenai/tango/releases/tag/v0.4.0) - 2022-01-27

tango/common/from_params.py

@@ -141,7 +141,38 @@ def infer_method_params(
             # `from __future__ import annotation`, the annotation will be a str,
             # so we need to resolve it using `get_type_hints` from the typing module.
             # See https://www.python.org/dev/peps/pep-0563/ for more info.
-            parameters[param_name] = param.replace(annotation=get_type_hints(method)[param_name])
+            try:
+                parameters[param_name] = param.replace(
+                    annotation=get_type_hints(method)[param_name]
+                )
+            except TypeError as e:
+                if "'type' object is not subscriptable" in str(e):
+                    # This can happen when someone uses a type hint like `dict[str, str]`
+                    # instead of `Dict[str, str]`.
+                    err_msg = (
+                        f"Failed to parse the type annotation `{param.annotation}` "
+                        f"from `{cls.__qualname__}.{method.__name__}()`."
+                    )
+
+                    if "[" in param.annotation:
+                        # Check if there is an equivalent generic in the `typing` module.
+                        import typing
+
+                        type_, *_ = param.annotation.split("[", 1)
+                        for possible_typing_equivalent in {type_, type_.title()}:
+                            if hasattr(typing, possible_typing_equivalent):
+                                err_msg += (
+                                    f" Try using `{possible_typing_equivalent}` "
+                                    "from the `typing` module instead."
+                                )
+                                break
+
+                    new_e = TypeError(err_msg)
+                    new_e.__cause__ = e
+                    new_e.__cause__ = e
+                    raise new_e
+                else:
+                    raise
 
     if var_positional_key:
         del parameters[var_positional_key]