From 2852746d59e4d60c37ac4373e0696eec64c9f526 Mon Sep 17 00:00:00 2001
From: Charles Cooper <cooper.charles.m@gmail.com>
Date: Fri, 16 Feb 2024 08:29:50 -0500
Subject: [PATCH] fix: import error messages

fix import error messages by fixing compliance with the metapath
protocol. instead of always returning a module loader which errors out
if it can't find a module, return None early (from find_module) if we
can't find the module. this lets the system fall back to the system
error handling for not-found modules.
---
 boa/interpret.py | 39 ++++++++++++++++++++++++---------------
 1 file changed, 24 insertions(+), 15 deletions(-)

diff --git a/boa/interpret.py b/boa/interpret.py
index ae13c338..d9fac315 100644
--- a/boa/interpret.py
+++ b/boa/interpret.py
@@ -27,29 +27,38 @@
 
 
 class BoaImporter(importlib.abc.MetaPathFinder):
+    def __init__(self):
+        self._path_lookup = {}
+
     def find_module(self, fullname, package_path, target=None):
-        # Return a loader
-        return self
+        # note: maybe instead of looping, append path to package_path
+        path = Path(fullname.replace(".", "/")).with_suffix(".vy")
+
+        for prefix in package_path:
+            # for fullname == "x.y.z"
+            # prefix looks something like "<...>/site-packages/x"
+            to_try = Path(prefix).parent / path
+
+            if to_try.exists():
+                self._path_lookup[fullname] = to_try
+                return self
+
+        return None
 
     def load_module(self, fullname):
-        # Return a module
         if fullname in sys.modules:
             return sys.modules[fullname]
 
-        path = Path(fullname.replace(".", "/")).with_suffix(".vy")
-        for prefix in sys.path:
-            to_try = Path(prefix) / path
-            try:
-                ret = load_partial(to_try)
-                break
-            except (FileNotFoundError, NotADirectoryError):
-                pass
-        else:
-            raise ImportError(fullname)
+        # import system should guarantee this, but be paranoid
+        if fullname not in self._path_lookup:
+            raise ImportError(f"invariant violated: no lookup for {fullname}")
+
+        path = self._path_lookup[fullname]
+        ret = load_partial(path)
 
         # comply with PEP-302:
-        ret.__name__ = to_try.name
-        ret.__file__ = str(to_try)
+        ret.__name__ = path.name
+        ret.__file__ = str(path)
         sys.modules[fullname] = ret
         return ret