Rework linecache handling (#828)

* Rework linecache handling

* lint

* Add changelog

changelog.d/828.changes.rst

@@ -0,0 +1 @@
+Generated source code is now cached more efficiently for identical classes.

src/attr/_make.py

@@ -5,7 +5,6 @@
 import linecache
 import sys
 import threading
-import uuid
 import warnings
 
 from operator import itemgetter
@@ -329,16 +328,25 @@ def _make_method(name, script, filename, globs=None):
     if globs is None:
         globs = {}
 
-    _compile_and_eval(script, globs, locs, filename)
-
     # In order of debuggers like PDB being able to step through the code,
     # we add a fake linecache entry.
-    linecache.cache[filename] = (
-        len(script),
-        None,
-        script.splitlines(True),
-        filename,
-    )
+    count = 1
+    base_filename = filename
+    while True:
+        linecache_tuple = (
+            len(script),
+            None,
+            script.splitlines(True),
+            filename,
+        )
+        old_val = linecache.cache.setdefault(filename, linecache_tuple)
+        if old_val == linecache_tuple:
+            break
+        else:
+            filename = "{}-{}>".format(base_filename[:-1], count)
+            count += 1
+
+    _compile_and_eval(script, globs, locs, filename)
 
     return locs[name]
 
@@ -1632,30 +1640,12 @@ def _generate_unique_filename(cls, func_name):
     """
     Create a "filename" suitable for a function being generated.
     """
-    unique_id = uuid.uuid4()
-    extra = ""
-    count = 1
-
-    while True:
-        unique_filename = "<attrs generated {0} {1}.{2}{3}>".format(
-            func_name,
-            cls.__module__,
-            getattr(cls, "__qualname__", cls.__name__),
-            extra,
-        )
-        # To handle concurrency we essentially "reserve" our spot in
-        # the linecache with a dummy line.  The caller can then
-        # set this value correctly.
-        cache_line = (1, None, (str(unique_id),), unique_filename)
-        if (
-            linecache.cache.setdefault(unique_filename, cache_line)
-            == cache_line
-        ):
-            return unique_filename
-
-        # Looks like this spot is taken. Try again.
-        count += 1
-        extra = "-{0}".format(count)
+    unique_filename = "<attrs generated {0} {1}.{2}>".format(
+        func_name,
+        cls.__module__,
+        getattr(cls, "__qualname__", cls.__name__),
+    )
+    return unique_filename
 
 
 def _make_hash(cls, attrs, frozen, cache_hash):

tests/test_dunders.py

@@ -936,6 +936,16 @@ class C(object):
     pass
 
 
+CopyC = C
+
+
+@attr.s(hash=True, order=True)
+class C(object):
+    """A different class, to generate different methods."""
+
+    a = attr.ib()
+
+
 class TestFilenames(object):
     def test_filenames(self):
         """
@@ -953,15 +963,27 @@ def test_filenames(self):
             OriginalC.__hash__.__code__.co_filename
             == "<attrs generated hash tests.test_dunders.C>"
         )
+        assert (
+            CopyC.__init__.__code__.co_filename
+            == "<attrs generated init tests.test_dunders.C>"
+        )
+        assert (
+            CopyC.__eq__.__code__.co_filename
+            == "<attrs generated eq tests.test_dunders.C>"
+        )
+        assert (
+            CopyC.__hash__.__code__.co_filename
+            == "<attrs generated hash tests.test_dunders.C>"
+        )
         assert (
             C.__init__.__code__.co_filename
-            == "<attrs generated init tests.test_dunders.C-2>"
+            == "<attrs generated init tests.test_dunders.C-1>"
         )
         assert (
             C.__eq__.__code__.co_filename
-            == "<attrs generated eq tests.test_dunders.C-2>"
+            == "<attrs generated eq tests.test_dunders.C-1>"
         )
         assert (
             C.__hash__.__code__.co_filename
-            == "<attrs generated hash tests.test_dunders.C-2>"
+            == "<attrs generated hash tests.test_dunders.C-1>"
         )