Print unified diff on test suite failures

Compares the .config's generated by us and the C implementation. Speeds
up debugging compared to manually generating them.

Clean up the test code a bit too.

1 files changed, 25 insertions, 17 deletions

diff --git a/testsuite.py b/testsuite.py
index 5263720..5a870f6 100644
--- a/testsuite.py
+++ b/testsuite.py
@@ -40,6 +40,7 @@
 
 from __future__ import print_function
 
+import difflib
 import errno
 import kconfiglib
 import os
@@ -2095,11 +2096,10 @@ def run_compatibility_tests():
                 del os.environ["SRCARCH"]
 
             if compare_configs:
-                sys.stdout.write("  {:14}".format(arch))
                 if equal_confs():
-                    print("OK")
+                    print("  {:14}OK".format(arch))
                 else:
-                    print("FAIL")
+                    print("  {:14}FAIL".format(arch))
                     fail()
 
     if all_ok():
@@ -2431,30 +2431,38 @@ def rm_configs():
     rm_if_exists("._config")
 
 def equal_confs():
-    with open(".config") as menu_conf:
-        l1 = menu_conf.readlines()
+    with open(".config") as f:
+        their = f.readlines()
+
+    # Strip the header generated by 'conf'
+    i = 0
+    for line in their:
+        if not line.startswith("#") or \
+           re.match(r"# CONFIG_(\w+) is not set", line):
+            break
+        i += 1
+    their = their[i:]
 
     try:
-        my_conf = open("._config")
+        f = open("._config")
     except IOError as e:
         if e.errno != errno.ENOENT:
             raise
         print("._config not found. Did you forget to apply the Makefile patch?")
         return False
     else:
-        with my_conf:
-            l2 = my_conf.readlines()
+        with f:
+            our = f.readlines()
 
-    # Skip the header generated by 'conf'
-    unset_re = r"# CONFIG_(\w+) is not set"
-    i = 0
-    for line in l1:
-        if not line.startswith("#") or \
-           re.match(unset_re, line):
-            break
-        i += 1
+    if their == our:
+        return True
+
+    # Print a unified diff to help debugging
+    print("Mismatched .config's! Unified diff:")
+    sys.stdout.writelines(difflib.unified_diff(their, our, fromfile="their",
+                                               tofile="our"))
 
-    return l1[i:] == l2
+    return False
 
 _all_ok = True