Update diff line number change calculation (#670)

* update calc num lines to include subtracted lines

* add more helpful messages

* add more unit tests and use set list

Author: clavedeluna

src/codemodder/codemods/test/utils.py

@@ -93,7 +93,11 @@ def run_and_assert(
             return
 
         assert len(changes) == 1
-        assert len(changes[0].changes) == num_changes
+        assert (
+            actual_num := len(changes[0].changes)
+        ) == num_changes, (
+            f"Expected {num_changes} changes but {actual_num} were created."
+        )
 
         self.assert_changes(
             tmpdir,
@@ -196,7 +200,11 @@ def run_and_assert(
             return
 
         assert len(changes) == 1
-        assert len(changes[0].changes) == num_changes
+        assert (
+            actual_num := len(changes[0].changes)
+        ) == num_changes, (
+            f"Expected {num_changes} changes but {actual_num} were created."
+        )
 
         self.assert_changes(
             tmpdir,

src/codemodder/diff.py

@@ -22,36 +22,47 @@ def create_diff_and_linenums(
     original_lines: list[str], new_lines: list[str]
 ) -> tuple[str, list[int]]:
     diff_lines = list(difflib.unified_diff(original_lines, new_lines))
-    return difflines_to_str(diff_lines), calc_new_line_nums(diff_lines)
+    return difflines_to_str(diff_lines), calc_line_num_changes(diff_lines)
 
 
-def calc_new_line_nums(diff_lines: list[str]) -> list[int]:
+def calc_line_num_changes(diff_lines: list[str]) -> list[int]:
+    """
+    Calculates the line numbers changed from a list of diff lines
+    Returns a list with unique elements.
+    """
     if not diff_lines:
         return []
 
-    added_line_nums = []
+    changed_line_nums: list[int] = []
     current_line_number = 0
+    original_line_number = 0
 
     for line in diff_lines:
         if line.startswith("@@"):
             # Extract the starting line number for the updated file from the diff metadata.
             # The format is @@ -x,y +a,b @@, where a is the starting line number in the updated file.
-            start_line = line.split(" ")[2]
-            current_line_number = (
-                int(start_line.split(",")[0][1:]) - 1
-            )  # Subtract 1 because line numbers are 1-indexed
+            start_line_original, start_line_updated = line.split(" ")[1:3]
+            original_line_number = int(start_line_original.split(",")[0][1:]) - 1
+            current_line_number = int(start_line_updated.split(",")[0][1:]) - 1
 
         elif line.startswith("+"):
             # Increment line number for each line in the updated file
             current_line_number += 1
-            if not line.startswith("++"):  # Ignore the diff metadata lines
-                added_line_nums.append(current_line_number)
-
-        elif not line.startswith("-"):
-            # Increment line number for unchanged/context lines
+            if not line.startswith("+++"):  # Ignore the diff metadata lines
+                changed_line_nums.append(current_line_number)
+
+        elif line.startswith("-"):
+            # Increment line number for each line in the original file
+            original_line_number += 1
+            if not line.startswith("---"):  # Ignore the diff metadata lines
+                changed_line_nums.append(original_line_number)
+
+        else:
+            # Increment line numbers for unchanged/context lines
+            original_line_number += 1
             current_line_number += 1
 
-    return added_line_nums
+    return list(set(changed_line_nums))
 
 
 def difflines_to_str(diff_lines: list[str]) -> str:

tests/test_diff.py

@@ -0,0 +1,61 @@
+from codemodder.diff import calc_line_num_changes
+
+
+def test_calc_line_nums_remove_line():
+    lines = [
+        "--- \n",
+        "+++ \n",
+        "@@ -5,7 +5,6 @@\n",
+        "     port: 443,\n",
+        "     path: '/',\n",
+        "     method: 'GET',\n",
+        "-    checkServerIdentity: function() {},\n",
+        " };\n",
+        " \n",
+        " const req = https.request(options, (res) => {\n",
+    ]
+    assert calc_line_num_changes(lines) == [8]
+
+
+def test_calc_line_nums_add_line():
+    lines = [
+        "--- original.py",
+        "+++ modified.py",
+        "@@ -1,3 +1,4 @@",
+        " def test_name(self):",
+        "     codemod = get_codemod()",
+        "+    print(codemod)",
+        '     assert codemod.name == "django", f"incorrect name"',
+    ]
+    assert calc_line_num_changes(lines) == [3]
+
+
+def test_calc_line_nums_change_same_line():
+    lines = [
+        "--- original.py",
+        "+++ modified.py",
+        "@@ -1,4 +1,4 @@",
+        " def test_name(self):",
+        "     codemod = get_codemod()",
+        "-    assert codemod.name == 'django'",
+        "+    assert codemod.name == 'django', f'incorrect name'",
+    ]
+    assert calc_line_num_changes(lines) == [3]
+
+
+def test_calc_line_nums_multiple_hunks():
+    lines = [
+        "--- one.txt	2024-06-28 11:52:23",
+        "+++ two.txt	2024-06-28 11:52:13",
+        "@@ -1,3 +1,9 @@",
+        " def test_name(self):",
+        "     codemod = get_codemod()",
+        "+    print(codemod)",
+        '     assert codemod.name == "django", f"incorrect name"',
+        '+    print("test OK")',
+        "+",
+        "+",
+        "+def test_new():",
+        "+    pass",
+    ]
+    assert calc_line_num_changes(lines) == [3, 5, 6, 7, 8, 9]