Var replace

Dockerfile

@@ -4,7 +4,7 @@ COPY dfupdate.py /dfupdate.py
 
 COPY docker-entrypoint.sh /docker-entrypoint.sh
 
-ENV DFUPDATE_VERSION 2.2.1
+ENV DFUPDATE_VERSION 2.2.2
 ENV REQUESTS_VERSION 2.32.5
 ENV TENACITY_VERSION 9.1.2
 ENV DOCKERFILE_PARSE_VERSION 2.0.1

dfupdate.py

@@ -262,6 +262,30 @@ def _update_env_value(self, env_name: str, new_value: str) -> bool:
             )
         return changed
 
+    def _substitute_version_tokens(
+        self, text: str | None, sw: str, new_ver: str, current_example: str
+    ) -> str:
+        """
+        Replace common version placeholders with the new version.
+        Supports ${SW_VERSION}, $SW_VERSION, and the literal current version string.
+        """
+        if not text:
+            return ""
+        sw_upper = sw.upper()
+        sw_lower = sw.lower()
+        placeholders = [
+            f"${{{sw_upper}_VERSION}}",
+            f"${sw_upper}_VERSION",
+            f"${{{sw_lower}_VERSION}}",
+            f"${sw_lower}_VERSION",
+        ]
+        result = text
+        for placeholder in placeholders:
+            result = result.replace(placeholder, new_ver)
+        if current_example:
+            result = result.replace(current_example, new_ver)
+        return result
+
     def _get_env_value(
         self, env_name: str, stage_index: int | None = None
     ) -> str | None:
@@ -492,8 +516,13 @@ def update_software(self, sw: str, new_ver: str, current_versions: set[str]):
         df_sha = self._get_env_value(f"{sw}_SHA256", stage_hint)
         if df_url and df_filename and df_sha:
             logger.info("Found remote URL, fetching and calculating new shasum")
-            full_url = df_url + "/" + df_filename
-            full_url = full_url.replace(current_example, new_ver)
+            url_template = self._substitute_version_tokens(
+                df_url, sw, new_ver, current_example
+            )
+            filename_template = self._substitute_version_tokens(
+                df_filename, sw, new_ver, current_example
+            )
+            full_url = url_template.rstrip("/") + "/" + filename_template.lstrip("/")
             logger.info("Retrieving new SHA256 for %s from %s", sw, full_url)
             new_sha = get_remote_sha(full_url)
             if new_sha:

test_dfupdate.py

@@ -130,7 +130,7 @@ def test_update_base_multi_stage(self):
         self.assertIn("FROM python:3.11 AS builder", content)
         self.assertIn("FROM alpine:3.19", content)
 
-    @mock.patch("dfupdate.get_remote_sha", return_value="deadbeef")
+    @mock.patch("dfupdate.get_remote_sha", return_value="jytncge6")
     def test_check_software_updates_across_stages(self, _msha):
         self._write_dockerfile(
             "FROM python:3.10 AS builder\n"
@@ -148,8 +148,38 @@ def test_check_software_updates_across_stages(self, _msha):
         with open(self.dockerfile_path, "r", encoding="utf8") as fh:
             content = fh.read()
         self.assertEqual(content.count("FOO_VERSION=2.0"), 2)
-        self.assertIn("FOO_SHA256=deadbeef", content)
-        self.assertIn("FOO_SHA256 deadbeef", content)
+        self.assertIn("FOO_SHA256=jytncge6", content)
+        self.assertIn("FOO_SHA256 jytncge6", content)
+
+    @mock.patch("dfupdate.get_remote_sha", return_value="jytncge6")
+    def test_update_replaces_version_placeholders_in_url_and_filename(self, msha):
+        self._write_dockerfile(
+            "FROM alpine\n"
+            "ENV UV_VERSION=0.9.15\n"
+            "ENV UV_URL=https://github.com/astral-sh/uv/releases/download/${UV_VERSION}\n"
+            "ENV UV_FILENAME=uv-$UV_VERSION.tar.gz\n"
+            "ENV UV_SHA256=old\n"
+        )
+        with open(self.nvchecker_path, "w", encoding="utf8") as fh:
+            json.dump({"UV": {"version": "0.9.17"}}, fh)
+        self.updater.update()
+        used_url = msha.call_args.args[0]
+        self.assertNotIn("${UV_VERSION}", used_url)
+        self.assertNotIn("$UV_VERSION", used_url)
+        self.assertIn("0.9.17", used_url)
+        with open(self.dockerfile_path, "r", encoding="utf8") as fh:
+            content = fh.read()
+        self.assertIn("UV_VERSION=0.9.17", content)
+        self.assertIn("UV_SHA256=jytncge6", content)
+
+    def test_update_detects_newer_version_and_writes(self):
+        self._write_dockerfile("FROM alpine\nENV UV_VERSION=0.9.15\n")
+        with open(self.nvchecker_path, "w", encoding="utf8") as fh:
+            json.dump({"UV": {"version": "0.9.17"}}, fh)
+        self.updater.update()
+        with open(self.dockerfile_path, "r", encoding="utf8") as fh:
+            content = fh.read()
+        self.assertIn("UV_VERSION=0.9.17", content)
 
 
 class TestParseArgs(unittest.TestCase):