Enhance fact_diff to show common lines (#323)

* Enhance fact_diff to show common lines

* Add integration and unit tests

* Fix sanity

---------

Co-authored-by: Ashwini Mhatre <amhatre@amhatre-thinkpadt14sgen2i.pnq.csb>

changelogs/fragments/Fre_fact_diff.yaml

@@ -0,0 +1,3 @@
+---
+minor_changes:
+  - Add support in fact_diff filter plugin to show common lines.(https://github.com/ansible-collections/ansible.utils/issues/311)

docs/ansible.utils.fact_diff_filter.rst

@@ -70,6 +70,27 @@ Parameters
                         <div>The first fact to be used in the comparison.</div>
                 </td>
             </tr>
+            <tr>
+                <td colspan="3">
+                    <div class="ansibleOptionAnchor" id="parameter-"></div>
+                    <b>common</b>
+                    <a class="ansibleOptionLink" href="#parameter-" title="Permalink to this option"></a>
+                    <div style="font-size: small">
+                        <span style="color: purple">boolean</span>
+                    </div>
+                </td>
+                <td>
+                        <ul style="margin: 0; padding: 0"><b>Choices:</b>
+                                    <li><div style="color: blue"><b>no</b>&nbsp;&larr;</div></li>
+                                    <li>yes</li>
+                        </ul>
+                </td>
+                    <td>
+                    </td>
+                <td>
+                        <div>Show all common lines.</div>
+                </td>
+            </tr>
             <tr>
                 <td colspan="3">
                     <div class="ansibleOptionAnchor" id="parameter-"></div>

plugins/filter/fact_diff.py

@@ -59,6 +59,11 @@ DOCUMENTATION = """
                     comparison
                 type: list
                 elements: str
+      common:
+        description:
+          - Show all common lines.
+        type: bool
+        default: false
 """
 
 EXAMPLES = """
@@ -185,7 +190,7 @@ except ImportError:
 def _fact_diff(*args, **kwargs):
     """Find the difference between currently set facts"""
 
-    keys = ["before", "after", "plugin"]
+    keys = ["before", "after", "plugin", "common"]
     data = dict(zip(keys, args[1:]))
     data.update(kwargs)
     aav = AnsibleArgSpecValidator(data=data, schema=DOCUMENTATION, name="fact_diff")

plugins/plugin_utils/fact_diff.py

@@ -10,8 +10,11 @@ The fact_diff plugin code
 """
 from __future__ import absolute_import, division, print_function
 
+import difflib
 import re
 
+from collections.abc import MutableMapping
+
 from ansible.plugins.callback import CallbackBase
 
 
@@ -31,7 +34,7 @@ def _raise_error(msg):
     raise AnsibleFilterError(error)
 
 
-def fact_diff(before, after, plugin):
+def fact_diff(before, after, plugin, common):
     """Compare two facts or variables and get a diff.
     :param before: The first fact to be used in the comparison.
     :type before: raw
@@ -40,46 +43,103 @@ def fact_diff(before, after, plugin):
     :param plugin: The name of the plugin in collection format
     :type plugin: string
     """
-    result = run_diff(before, after, plugin)
+    if plugin.get("name") == "ansible.utils.native":
+        result = fact_diff_native().run_diff(before, after, plugin, common)
     return result
 
 
-def _check_valid_regexes(skip_lines):
+class fact_diff_native(CallbackBase):
-    if skip_lines:
+    def _check_valid_regexes(self, skip_lines):
-        for idx, regex in enumerate(skip_lines):
+        if skip_lines:
-            try:
+            for idx, regex in enumerate(skip_lines):
-                skip_lines[idx] = re.compile(regex)
+                try:
-            except re.error as exc:
+                    skip_lines[idx] = re.compile(regex)
-                msg = "The regex '{regex}', is not valid. The error was {err}.".format(
+                except re.error as exc:
-                    regex=regex,
+                    msg = "The regex '{regex}', is not valid. The error was {err}.".format(
-                    err=str(exc),
+                        regex=regex,
+                        err=str(exc),
+                    )
+                    _raise_error(msg)
+
+    def _xform(self, before, after, skip_lines):
+        if skip_lines:
+            if isinstance(before, str):
+                before = before.splitlines()
+            if isinstance(after, str):
+                after = after.splitlines()
+            before = [
+                line for line in before if not any(regex.match(str(line)) for regex in skip_lines)
+            ]
+            after = [
+                line for line in after if not any(regex.match(str(line)) for regex in skip_lines)
+            ]
+        if isinstance(before, list):
+            before = "\n".join(map(str, before)) + "\n"
+        if isinstance(after, list):
+            after = "\n".join(map(str, after)) + "\n"
+        return before, after, skip_lines
+
+    def get_fact_diff(self, difflist):
+        if not isinstance(difflist, list):
+            difflist = [difflist]
+        ret = []
+        for diff in difflist:
+            if "before" in diff and "after" in diff:
+                # format complex structures into 'files'
+                for x in ["before", "after"]:
+                    if isinstance(diff[x], MutableMapping):
+                        diff[x] = self._serialize_diff(diff[x])
+                    elif diff[x] is None:
+                        diff[x] = ""
+                if "before_header" in diff:
+                    before_header = "before: %s" % diff["before_header"]
+                else:
+                    before_header = "before"
+                if "after_header" in diff:
+                    after_header = "after: %s" % diff["after_header"]
+                else:
+                    after_header = "after"
+                before_lines = diff["before"].splitlines(True)
+                after_lines = diff["after"].splitlines(True)
+                if before_lines and not before_lines[-1].endswith("\n"):
+                    before_lines[-1] += "\n\\ No newline at end of file\n"
+                if after_lines and not after_lines[-1].endswith("\n"):
+                    after_lines[-1] += "\n\\ No newline at end of file\n"
+                diff_context = (
+                    len(before_lines) if len(before_lines) > len(after_lines) else len(after_lines)
                 )
-                _raise_error(msg)
+                differ = difflib.unified_diff(
+                    before_lines,
+                    after_lines,
+                    fromfile=before_header,
+                    tofile=after_header,
+                    fromfiledate="",
+                    tofiledate="",
+                    n=diff_context,
+                )
+                difflines = list(differ)
+                has_diff = False
+                for line in difflines:
+                    has_diff = True
+                    if diff["common"]:
+                        if line.startswith("+") or line.startswith("-"):
+                            pass
+                        else:
+                            ret.append(line)
+                    else:
+                        ret.append(line)
+                if has_diff:
+                    ret.append("\n")
+            if "prepared" in diff:
+                ret.append(diff["prepared"])
+        return "".join(ret)
 
-
+    def run_diff(self, before, after, plugin, common):
-def _xform(before, after, skip_lines):
+        skip_lines = plugin["vars"].get("skip_lines")
-    if skip_lines:
+        self._check_valid_regexes(skip_lines=skip_lines)
-        if isinstance(before, str):
+        before, after, skip_lines = self._xform(before, after, skip_lines=skip_lines)
-            before = before.splitlines()
+        diff = self.get_fact_diff({"before": before, "after": after, "common": common})
-        if isinstance(after, str):
+        ansi_escape = re.compile(r"\x1B[@-_][0-?]*[ -/]*[@-~]")
-            after = after.splitlines()
+        diff_text = ansi_escape.sub("", diff)
-        before = [
+        result = list(diff_text.splitlines())
-            line for line in before if not any(regex.match(str(line)) for regex in skip_lines)
+        return result
-        ]
-        after = [line for line in after if not any(regex.match(str(line)) for regex in skip_lines)]
-    if isinstance(before, list):
-        before = "\n".join(map(str, before)) + "\n"
-    if isinstance(after, list):
-        after = "\n".join(map(str, after)) + "\n"
-    return before, after, skip_lines
-
-
-def run_diff(before, after, plugin):
-    skip_lines = plugin["vars"].get("skip_lines")
-    _check_valid_regexes(skip_lines=skip_lines)
-    before, after, skip_lines = _xform(before, after, skip_lines=skip_lines)
-    diff = CallbackBase()._get_diff({"before": before, "after": after})
-    ansi_escape = re.compile(r"\x1B[@-_][0-?]*[ -/]*[@-~]")
-    diff_text = ansi_escape.sub("", diff)
-    result = list(diff_text.splitlines())
-    return result

tests/integration/targets/utils_fact_diff/tasks/filter.yaml

@@ -20,28 +20,16 @@
     msg: "The regex '+', is not valid"
 
 - name: Check argspec validation
-  ansible.builtin.set_fact: "{{ ansible.utils.fact_diff([1, 2, 3]) }}"
+  ansible.builtin.set_fact:
+    result: "{{ [1, 2, 3] | ansible.utils.fact_diff() }}"
+  register: error
   ignore_errors: true
-  register: result
 
 - name: Assert
   ansible.builtin.assert:
-    that: "{{ msg in result.msg }}"
+    that: "{{ msg in error.msg }}"
   vars:
     msg: "missing required arguments: after"
-  when: "result.msg | type_debug == 'list'"
-
-- name: Check argspec validation
-  ansible.builtin.set_fact: "{{ ansible.utils.fact_diff([1, 2, 3]) }}"
-  ignore_errors: true
-  register: result
-
-- name: Assert
-  ansible.builtin.assert:
-    that: "{{ msg in result.msg }}"
-  vars:
-    msg: "missing required arguments: before"
-  when: "result.msg | type_debug == 'list'"
 
 - name: Set fact
   ansible.builtin.set_fact:
@@ -69,7 +57,7 @@
     before: "{{ before | ansible.utils.to_paths }}"
     after: "{{ after | ansible.utils.to_paths }}"
 
-- name: Show the difference in json format
+- name: Show the difference in path format
   ansible.builtin.set_fact:
     result: "{{ before | ansible.utils.fact_diff(after) }}"
 
@@ -78,6 +66,27 @@
     before: "{{ before | to_nice_yaml }}"
     after: "{{ after | to_nice_yaml }}"
 
-- name: Show the difference in json format
+- name: Show the difference in yaml format
   ansible.builtin.set_fact:
     result: "{{ before | ansible.utils.fact_diff(after) }}"
+
+- name: Set fact
+  ansible.builtin.set_fact:
+    before:
+      a:
+        b:
+          c:
+            d:
+              - 0
+              - 1
+    after:
+      a:
+        b:
+          c:
+            d:
+              - 2
+              - 3
+
+- name: Show the common lines in json format
+  ansible.builtin.set_fact:
+    result: "{{ before | ansible.utils.fact_diff(after, common=true) }}"

tests/unit/plugins/filter/test_fact_diff.py

@@ -106,3 +106,13 @@ class TestUpdate_Fact(unittest.TestCase):
             "missing required arguments: after",
             str(error.exception),
         )
+
+    def test_diff_dict_common(self):
+        """Compare two dicts that with common option"""
+        self.maxDiff = None
+        before = {"a": {"b": {"c": {"d": [0, 1, 2, 3]}}}}
+        after = {"a": {"b": {"c": {"d": [0, 1, 2, 4]}}}}
+        result = _fact_diff("", before, after, common=True)
+        self.assertIn("                    0", result)
+        self.assertIn("                    1", result)
+        self.assertIn("                    2", result)