yaml-diff.py: Making it a bit better

Adding a --details switch to have a bit more information about the
differences between yaml files.

This is pretty much leveraging the difflib to get at most 2 levels of
differences in the yaml structure.

Change-Id: If300a5f5d351404dbcf73d02822cdccf8e9f68df

tools/yaml-diff.py

@@ -11,14 +11,78 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import argparse
+from collections import defaultdict
+import difflib
+from pprint import pformat
 import sys
 import yaml
 
-if len(sys.argv) != 3:
-    raise RuntimeError('Not enough arguemnts')
+COMPARE_SECTIONS = ['parameters', 'conditions', 'resources', 'outputs']
 
-FILE_A = sys.argv[1]
-FILE_B = sys.argv[2]
+
+def parse_args():
+    p = argparse.ArgumentParser()
+
+    p.add_argument('--details', '-d',
+                   action='count',
+                   default=0,
+                   help='Show details, deeper comparison with -dd')
+    p.add_argument('--common', '-c',
+                   action='store_true',
+                   help='Show common items when comparing sections')
+    p.add_argument('--section', '-s',
+                   action='store',
+                   nargs='*',
+                   help="Sections to compare",
+                   default=COMPARE_SECTIONS)
+    p.add_argument('path_args', action='store', nargs='*')
+
+    args = p.parse_args()
+    if len(args.path_args) != 2:
+        p.error("Need two files to compare")
+
+    return args
+
+
+def diff_list(list_a, list_b):
+    """Takes 2 lists and returns the differences between them"""
+    list_a = sorted(list_a)
+    list_b = sorted(list_b)
+    diffs = defaultdict(list)
+    sequence = difflib.SequenceMatcher(None, list_a, list_b).get_opcodes()
+    for tag, i, j, k, l in sequence:
+        if tag == 'equal' and show_common:
+            diffs['common'].extend(list_a[i:j])
+        if tag in ('delete', 'replace'):
+            diffs[FILE_A].extend(list_a[i:j])
+        if tag in ('insert', 'replace'):
+            diffs[FILE_B].extend(list_b[k:l])
+    return "\n".join([f"{fn} {dl}" for fn, dl in diffs.items()])
+
+
+def diff_dict(dict_a, dict_b):
+    """Compares two dicts
+
+    Converts 2 dicts to strings with pformat and returns
+    a unified diff formated string
+    """
+    return "\n".join([d for d in difflib.unified_diff(
+        pformat(dict_a, width=80).splitlines(),
+        pformat(dict_b, width=80).splitlines(),
+        fromfile=FILE_A,
+        tofile=FILE_B)])
+
+
+args = parse_args()
+
+path_args = args.path_args
+show_details = args.details
+show_common = args.common
+sections = args.section
+
+FILE_A = path_args[0]
+FILE_B = path_args[1]
 
 with open(FILE_A, 'r') as file_a:
     a = yaml.safe_load(file_a)
@@ -26,7 +90,37 @@ with open(FILE_A, 'r') as file_a:
 with open(FILE_B, 'r') as file_b:
     b = yaml.safe_load(file_b)
 
-if a != b:
-    sys.exit("Files are different")
+exit = "Files are different" if a != b else 0
 
-sys.exit(0)
+if not show_details:
+    sys.exit(exit)
+
+# With -ddd, we print the full diff dict and exit
+if show_details >= 3:
+    print(diff_dict(a, b))
+    sys.exit(exit)
+
+section_diff = diff_list(list(a.keys()), list(a.keys()))
+if section_diff:
+    print(f"Sections list\n{section_diff}")
+
+for item in sections:
+    keys_a = list(a.get(item).keys())
+    keys_b = list(b.get(item).keys())
+    section_item_diff = diff_list(keys_a, keys_b)
+    if section_item_diff:
+        print(f"\n\nSection {item}\n{section_item_diff}")
+    if show_details > 1:
+        for key in list(set(keys_a + keys_b)):
+            key_a = a.get(item, {}).get(key, {})
+            key_b = b.get(item, {}).get(key, {})
+            diff = diff_dict(key_a, key_b)
+            # If a key is missing from either list, we don't want
+            # to see the full diff, it's already flagged when
+            # show_details == 1
+            # We just want to see if child dict is existent on both sides
+            # and different
+            if diff and key_a and key_b:
+                print(f"\n\n{item}/{key}\n{diff}")
+
+sys.exit(exit)