Better import hook (#35)

jaxtyping/__init__.py

@@ -67,4 +67,4 @@ class Array:
 from .pytree_type import PyTree
 
 
-__version__ = "0.2.6"
+__version__ = "0.2.7"

jaxtyping/import_hook.py

@@ -65,7 +65,9 @@ def _call_with_frames_removed(f, *args, **kwargs):
 
 
 def _optimized_cache_from_source(path, debug_override=None):
-    return cache_from_source(path, debug_override, optimization="jaxtyping")
+    # Version 2: change the position of the `@jaxtyped` decorator, so need a
+    # different name to avoid hitting old __pycache__
+    return cache_from_source(path, debug_override, optimization="jaxtyping2")
 
 
 class _JaxtypingTransformer(ast.NodeVisitor):
@@ -99,10 +101,16 @@ def visit_FunctionDef(self, node: ast.FunctionDef):
         has_annotated_args = any(arg for arg in node.args.args if arg.annotation)
         has_annotated_return = bool(node.returns)
         if has_annotated_args or has_annotated_return:
-            # Place at the start of the decorator list, in case a typechecking
-            # annotation has been manually applied; we need to be above that.
-            node.decorator_list.insert(
-                0,
+            # Place at the end of the decorator list, as otherwise we wrap e.g.
+            # `jax.custom_{jvp,vjp}` and lose the ability to `defjvp` etc.
+            #
+            # Note that the counter-argument here is that we'd like to place this
+            # at the start of the decorator list, in case a typechecking annotation
+            # has been manually applied, and we'd need to be above that. In this
+            # case we're just going to have to need to ask the user to remove their
+            # typechecking annotation (and let this decorator do it instead).
+            # It's more important we be compatible with normal JAX code.
+            node.decorator_list.append(
                 ast.Attribute(
                     ast.Name(id="jaxtyping", ctx=ast.Load()), "jaxtyped", ast.Load()
                 ),
@@ -230,8 +238,16 @@ def install_import_hook(
     - `typechecker`: the module and function of the typechecker you want to use, as a
         2-tuple of strings. For example `typechecker=("typeguard", "typechecked")` or
         `typechecker=("beartype", "beartype")`. You may pass `typechecker=None` if you
-        do not want to automatically decorate with a typechecker as well; e.g. if you
-        have a codebase that already has these decorators.
+        do not want to automatically decorate with a typechecker as well.
+
+    If the function already has any decorators on it, then both the `@jaxtyped` and the
+    typechecker decorators will go at the bottom of the decorator list, e.g.
+    ```python
+    @some_other_decorator
+    @jaxtyped
+    @beartype.beartype
+    def foo(...): ...
+    ```
 
     **Returns:**
 
@@ -243,8 +259,8 @@ def install_import_hook(
     ```python
     # entry_point.py
     from jaxtyped import install_import_hook
-    install_import_hook("main", ("beartype", "beartype"))
-    import main
+    with install_import_hook("main", ("beartype", "beartype"))
+        import main
     ...  # do whatever you're doing
 
     # main.py