config_mgmt: T4991: use configtree.show_diff instead of Python difflib

2 files changed, 44 insertions, 31 deletions

diff --git a/python/vyos/config_mgmt.py b/python/vyos/config_mgmt.py
index 22a49ff50..fade3081c 100644
--- a/python/vyos/config_mgmt.py
+++ b/python/vyos/config_mgmt.py
@@ -24,7 +24,7 @@ from datetime import datetime
 from tabulate import tabulate
 
 from vyos.config import Config
-from vyos.configtree import ConfigTree
+from vyos.configtree import ConfigTree, ConfigTreeError, show_diff
 from vyos.defaults import directories
 from vyos.util import is_systemd_service_active, ask_yes_no, rc_cmd
 
@@ -93,15 +93,7 @@ class ConfigMgmt:
 
         # a call to compare without args is edit_level aware
         edit_level = os.getenv('VYATTA_EDIT_LEVEL', '')
-        edit_path = [l for l in edit_level.split('/') if l]
-        if edit_path:
-            eff_conf = config.show_config(edit_path, effective=True)
-            self.edit_level_active_config = ConfigTree(eff_conf)
-            conf = config.show_config(edit_path)
-            self.edit_level_working_config = ConfigTree(conf)
-        else:
-            self.edit_level_active_config = None
-            self.edit_level_working_config = None
+        self.edit_path = [l for l in edit_level.split('/') if l]
 
         self.active_config = config._running_config
         self.working_config = config._session_config
@@ -241,14 +233,8 @@ Proceed ?'''
         revision n vs. revision m; working version vs. active version;
         or working version vs. saved version.
         """
-        from difflib import unified_diff
-
-        ct1 = self.edit_level_active_config
-        if ct1 is None:
-            ct1 = self.active_config
-        ct2 = self.edit_level_working_config
-        if ct2 is None:
-            ct2 = self.working_config
+        ct1 = self.active_config
+        ct2 = self.working_config
         msg = 'No changes between working and active configurations.\n'
         if saved:
             ct1 = self._get_saved_config_tree()
@@ -268,19 +254,16 @@ Proceed ?'''
             ct1 = self._get_config_tree_revision(rev2)
             msg = f'No changes between revisions {rev2} and {rev1} configurations.\n'
 
-        if commands:
-            lines1 = ct1.to_commands().splitlines(keepends=True)
-            lines2 = ct2.to_commands().splitlines(keepends=True)
-        else:
-            lines1 = ct1.to_string().splitlines(keepends=True)
-            lines2 = ct2.to_string().splitlines(keepends=True)
-
         out = ''
-        comp = unified_diff(lines1, lines2)
-        for line in comp:
-            if re.match(r'(\-\-)|(\+\+)|(@@)', line):
-                continue
-            out += line
+        path = [] if commands else self.edit_path
+        try:
+            if commands:
+                out = show_diff(ct1, ct2, path=path, commands=True)
+            else:
+                out = show_diff(ct1, ct2, path=path)
+        except ConfigTreeError as e:
+            return e, 1
+
         if out:
             msg = out
 
diff --git a/python/vyos/configtree.py b/python/vyos/configtree.py
index f2358ee4f..c0b3ebd78 100644
--- a/python/vyos/configtree.py
+++ b/python/vyos/configtree.py
@@ -16,7 +16,7 @@ import os
 import re
 import json
 
-from ctypes import cdll, c_char_p, c_void_p, c_int
+from ctypes import cdll, c_char_p, c_void_p, c_int, c_bool
 
 LIBPATH = '/usr/lib/libvyosconfig.so.0'
 
@@ -322,6 +322,36 @@ class ConfigTree(object):
         subt = ConfigTree(address=res)
         return subt
 
+def show_diff(left, right, path=[], commands=False, libpath=LIBPATH):
+    if left is None:
+        left = ConfigTree(config_string='\n')
+    if right is None:
+        right = ConfigTree(config_string='\n')
+    if not (isinstance(left, ConfigTree) and isinstance(right, ConfigTree)):
+        raise TypeError("Arguments must be instances of ConfigTree")
+    if path:
+        if (not left.exists(path)) and (not right.exists(path)):
+            raise ConfigTreeError(f"Path {path} doesn't exist")
+
+    check_path(path)
+    path_str = " ".join(map(str, path)).encode()
+
+    __lib = cdll.LoadLibrary(libpath)
+    __show_diff = __lib.show_diff
+    __show_diff.argtypes = [c_bool, c_char_p, c_void_p, c_void_p]
+    __show_diff.restype = c_char_p
+    __get_error = __lib.get_error
+    __get_error.argtypes = []
+    __get_error.restype = c_char_p
+
+    res = __show_diff(commands, path_str, left._get_config(), right._get_config())
+    res = res.decode()
+    if res == "#1@":
+        msg = __get_error().decode()
+        raise ConfigTreeError(msg)
+
+    return res
+
 class DiffTree:
     def __init__(self, left, right, path=[], libpath=LIBPATH):
         if left is None: