Add module reloading tests

tests/importer/test_importer.py

@@ -3,10 +3,12 @@
 # license. See the LICENSE.
 
 import os
+import sys
 import ast
+import imp
 import tempfile
-import importlib
 import runpy
+import importlib
 
 from fractions import Fraction
 
@@ -14,6 +16,7 @@ import pytest
 
 import hy
 from hy.errors import HyTypeError
+from hy.lex import LexException
 from hy.compiler import hy_compile
 from hy.importer import hy_parse, HyLoader, cache_from_source
 
@@ -98,3 +101,100 @@ def test_eval():
         '(if True "this is if true" "this is if false")') == "this is if true"
     assert eval_str('(lfor num (range 100) :if (= (% num 2) 1) (pow num 2))') == [
         pow(num, 2) for num in range(100) if num % 2 == 1]
+
+
+def test_reload():
+    """Copied from CPython's `test_import.py`"""
+
+    def unlink(filename):
+        os.unlink(source)
+        bytecode = cache_from_source(source)
+        if os.path.isfile(bytecode):
+            os.unlink(bytecode)
+
+    TESTFN = 'testfn'
+    source = TESTFN + os.extsep + "hy"
+    with open(source, "w") as f:
+        f.write("(setv a 1)")
+        f.write("(setv b 2)")
+
+    sys.path.insert(0, os.curdir)
+    try:
+        mod = importlib.import_module(TESTFN)
+        assert TESTFN in sys.modules
+        assert mod.a == 1
+        assert mod.b == 2
+
+        # On WinXP, just replacing the .py file wasn't enough to
+        # convince reload() to reparse it.  Maybe the timestamp didn't
+        # move enough.  We force it to get reparsed by removing the
+        # compiled file too.
+        unlink(source)
+
+        # Now damage the module.
+        with open(source, "w") as f:
+            f.write("(setv a 10)")
+            f.write("(setv b (// 20 0))")
+
+        with pytest.raises(ZeroDivisionError):
+            imp.reload(mod)
+
+        # But we still expect the module to be in sys.modules.
+        mod = sys.modules.get(TESTFN)
+        assert mod is not None
+
+        # We should have replaced a w/ 10, but the old b value should
+        # stick.
+        assert mod.a == 10
+        assert mod.b == 2
+
+        # Now fix the issue and reload the module.
+        unlink(source)
+
+        with open(source, "w") as f:
+            f.write("(setv a 11)")
+            f.write("(setv b (// 20 1))")
+
+        imp.reload(mod)
+
+        mod = sys.modules.get(TESTFN)
+        assert mod is not None
+
+        assert mod.a == 11
+        assert mod.b == 20
+
+        # Now cause a LexException
+        unlink(source)
+
+        with open(source, "w") as f:
+            f.write("(setv a 11")
+            f.write("(setv b (// 20 1))")
+
+        with pytest.raises(LexException):
+            imp.reload(mod)
+
+        mod = sys.modules.get(TESTFN)
+        assert mod is not None
+
+        assert mod.a == 11
+        assert mod.b == 20
+
+        # Fix it and retry
+        unlink(source)
+
+        with open(source, "w") as f:
+            f.write("(setv a 12)")
+            f.write("(setv b (// 10 1))")
+
+        imp.reload(mod)
+
+        mod = sys.modules.get(TESTFN)
+        assert mod is not None
+
+        assert mod.a == 12
+        assert mod.b == 10
+
+    finally:
+        del sys.path[0]
+        unlink(source)
+        del sys.modules[TESTFN]