fix: Handle tag@digest format in pull_image methods

When using combined image:tag@digest references, parse_repository_tag
returns (repo, "tag@digest"). The Docker SDK and API don't accept
tag@digest in the tag parameter, causing "invalid tag format" errors.

This fix:
1. Adds build_pull_arguments() helper function to _util.py
2. Uses the helper in both pull_image implementations
3. When tag contains @ (but isn't a pure digest), passes the full
   reference as the repository/fromImage parameter instead of splitting

Tested formats:
- portainer/portainer-ee:2.35.0-alpine@sha256:abc...
- ghcr.io/gethomepage/homepage:v1.7@sha256:abc...
- localhost:5000/myapp:v2.0@sha256:abc...

The existing filter_images_by_tag already handles tag@digest for
lookups, so find_image continues to work correctly.

Includes comprehensive unit tests for build_pull_arguments().

plugins/module_utils/_common.py

@@ -27,6 +27,7 @@ from ansible_collections.community.docker.plugins.module_utils._util import (
     DOCKER_COMMON_ARGS,
     DOCKER_MUTUALLY_EXCLUSIVE,
     DOCKER_REQUIRED_TOGETHER,
+    build_pull_arguments,
     filter_images_by_tag,
     sanitize_result,
     update_tls_hostname,
@@ -572,17 +573,22 @@ class AnsibleDockerClientBase(Client):
         """
         Pull an image
         """
-        kwargs = {
-            "tag": tag,
+        kwargs: dict[str, t.Any] = {
             "stream": True,
             "decode": True,
         }
         if image_platform is not None:
             kwargs["platform"] = image_platform
+
+        # Build pull arguments - handles combined tag@digest format
+        pull_name, pull_tag = build_pull_arguments(name, tag)
+        if pull_tag is not None:
+            kwargs["tag"] = pull_tag
+
         self.log(f"Pulling image {name}:{tag}")
         old_tag = self.find_image(name, tag)
         try:
-            for line in self.pull(name, **kwargs):
+            for line in self.pull(pull_name, **kwargs):
                 self.log(line, pretty_print=True)
                 if line.get("error"):
                     if line.get("errorDetail"):

plugins/module_utils/_common_api.py

@@ -56,6 +56,7 @@ from ansible_collections.community.docker.plugins.module_utils._util import (
     DOCKER_COMMON_ARGS,
     DOCKER_MUTUALLY_EXCLUSIVE,
     DOCKER_REQUIRED_TOGETHER,
+    build_pull_arguments,
     filter_images_by_tag,
     sanitize_result,
     update_tls_hostname,
@@ -531,10 +532,15 @@ class AnsibleDockerClientBase(Client):
         try:
             repository, image_tag = parse_repository_tag(name)
             registry, dummy_repo_name = auth.resolve_repository_name(repository)
-            params = {
-                "tag": tag or image_tag or "latest",
-                "fromImage": repository,
-            }
+
+            # Build pull arguments - handles combined tag@digest format
+            effective_tag = tag or image_tag or "latest"
+            pull_name, pull_tag = build_pull_arguments(repository, effective_tag)
+
+            params: dict[str, t.Any] = {"fromImage": pull_name}
+            if pull_tag is not None:
+                params["tag"] = pull_tag
+
             if image_platform is not None:
                 params["platform"] = image_platform
 

plugins/module_utils/_util.py

@@ -146,6 +146,36 @@ def filter_images_by_tag(
     return []
 
 
+def build_pull_arguments(
+    name: str, tag: str
+) -> tuple[str, str | None]:
+    """
+    Build the correct arguments for Docker pull operations.
+
+    Docker SDK and API don't accept combined "tag@digest" in the tag parameter.
+    This function handles the three formats:
+    - Tag-only: "v1.0" -> (name, "v1.0")
+    - Digest-only: "sha256:abc..." -> (name, "sha256:abc...")
+    - Combined tag@digest: "v1.0@sha256:abc..." -> ("name:v1.0@sha256:abc...", None)
+
+    Args:
+        name: Repository name (e.g., "nginx", "ghcr.io/user/repo")
+        tag: Tag, digest, or combined tag@digest
+
+    Returns:
+        Tuple of (pull_name, pull_tag) where:
+        - For combined format: pull_name is full reference, pull_tag is None
+        - For other formats: pull_name is just the name, pull_tag is the tag/digest
+    """
+    # Handle combined tag@digest format (e.g., "v1.0@sha256:abc123")
+    # The @ indicates a digest, but if it doesn't START with sha256:, it's combined
+    if "@" in tag and not tag.startswith("sha256:"):
+        tag_part, digest = tag.split("@", 1)
+        return f"{name}:{tag_part}@{digest}", None
+    else:
+        return name, tag
+
+
 def is_valid_tag(tag: str, allow_empty: bool = False) -> bool:
     """Check whether the given string is a valid docker tag name."""
     if not tag:

tests/unit/plugins/module_utils/test_pull_image.py

@@ -0,0 +1,214 @@
+# Copyright (c) Ansible Project
+# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+"""
+Tests for build_pull_arguments handling of tag@digest format.
+
+When users specify an image with both tag and digest (e.g., nginx:1.21@sha256:abc...),
+the parse_repository_tag function returns ("nginx", "1.21@sha256:abc...").
+
+The Docker SDK and API don't accept "tag@digest" in the tag parameter.
+build_pull_arguments handles this by:
+- Returning full reference as name when tag contains @
+- Returning None for tag in that case
+"""
+
+from __future__ import annotations
+
+import unittest
+
+from ansible_collections.community.docker.plugins.module_utils._util import (
+    build_pull_arguments,
+)
+
+
+SHA = "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+
+
+class TestBuildPullArguments(unittest.TestCase):
+    """Test cases for build_pull_arguments function."""
+
+    # ========== Tag-only tests ==========
+
+    def test_tag_only_simple(self) -> None:
+        """Tag-only should return name and tag separately."""
+        assert build_pull_arguments("nginx", "1.21") == ("nginx", "1.21")
+
+    def test_tag_only_latest(self) -> None:
+        """Latest tag should return name and tag separately."""
+        assert build_pull_arguments("nginx", "latest") == ("nginx", "latest")
+
+    def test_tag_only_with_registry(self) -> None:
+        """Tag-only with registry should return name and tag separately."""
+        assert build_pull_arguments("ghcr.io/user/repo", "v1.0") == (
+            "ghcr.io/user/repo",
+            "v1.0",
+        )
+
+    def test_tag_only_with_registry_port(self) -> None:
+        """Tag-only with registry port should return name and tag separately."""
+        assert build_pull_arguments("localhost:5000/myapp", "v2.0") == (
+            "localhost:5000/myapp",
+            "v2.0",
+        )
+
+    # ========== Digest-only tests ==========
+
+    def test_digest_only(self) -> None:
+        """Digest-only (sha256:...) should return name and digest separately."""
+        assert build_pull_arguments("nginx", f"sha256:{SHA}") == (
+            "nginx",
+            f"sha256:{SHA}",
+        )
+
+    def test_digest_only_with_registry(self) -> None:
+        """Digest-only with registry should return name and digest separately."""
+        assert build_pull_arguments("ghcr.io/user/repo", f"sha256:{SHA}") == (
+            "ghcr.io/user/repo",
+            f"sha256:{SHA}",
+        )
+
+    # ========== Combined tag@digest tests ==========
+
+    def test_combined_tag_digest_simple(self) -> None:
+        """Combined tag@digest should return full reference with None tag."""
+        assert build_pull_arguments("nginx", f"1.21@sha256:{SHA}") == (
+            f"nginx:1.21@sha256:{SHA}",
+            None,
+        )
+
+    def test_combined_tag_digest_with_user_repo(self) -> None:
+        """Combined tag@digest with user/repo should return full reference."""
+        assert build_pull_arguments("portainer/portainer-ee", f"2.35.0-alpine@sha256:{SHA}") == (
+            f"portainer/portainer-ee:2.35.0-alpine@sha256:{SHA}",
+            None,
+        )
+
+    def test_combined_tag_digest_with_ghcr(self) -> None:
+        """Combined tag@digest with GHCR should return full reference."""
+        assert build_pull_arguments("ghcr.io/gethomepage/homepage", f"v1.7@sha256:{SHA}") == (
+            f"ghcr.io/gethomepage/homepage:v1.7@sha256:{SHA}",
+            None,
+        )
+
+    def test_combined_tag_digest_with_registry_port(self) -> None:
+        """Combined tag@digest with registry port should return full reference."""
+        assert build_pull_arguments("localhost:5000/myapp", f"v2.0@sha256:{SHA}") == (
+            f"localhost:5000/myapp:v2.0@sha256:{SHA}",
+            None,
+        )
+
+    # ========== Edge cases ==========
+
+    def test_empty_tag_part_before_digest(self) -> None:
+        """Handle edge case where tag part is empty like '@sha256:...'."""
+        # This is an unusual case but should still work
+        assert build_pull_arguments("nginx", f"@sha256:{SHA}") == (
+            f"nginx:@sha256:{SHA}",
+            None,
+        )
+
+    def test_tag_with_hyphen_and_digest(self) -> None:
+        """Tag with hyphens and digest should work."""
+        assert build_pull_arguments("nginx", f"1.21-alpine@sha256:{SHA}") == (
+            f"nginx:1.21-alpine@sha256:{SHA}",
+            None,
+        )
+
+    def test_tag_with_dots_and_digest(self) -> None:
+        """Tag with dots and digest should work."""
+        assert build_pull_arguments("nginx", f"1.21.0@sha256:{SHA}") == (
+            f"nginx:1.21.0@sha256:{SHA}",
+            None,
+        )
+
+
+class TestBuildPullArgumentsIntegration(unittest.TestCase):
+    """Integration tests with parse_repository_tag."""
+
+    def test_full_flow_docker_hub(self) -> None:
+        """Test parse_repository_tag -> build_pull_arguments for Docker Hub."""
+        from ansible_collections.community.docker.plugins.module_utils._api.utils.utils import (
+            parse_repository_tag,
+        )
+
+        # User specifies: portainer/portainer-ee:2.35.0-alpine@sha256:abc...
+        image_ref = f"portainer/portainer-ee:2.35.0-alpine@sha256:{SHA}"
+        repo, tag = parse_repository_tag(image_ref)
+
+        # parse_repository_tag returns repo and combined tag@digest
+        assert repo == "portainer/portainer-ee"
+        assert tag == f"2.35.0-alpine@sha256:{SHA}"
+
+        # build_pull_arguments converts to full reference
+        pull_name, pull_tag = build_pull_arguments(repo, tag)
+        assert pull_name == f"portainer/portainer-ee:2.35.0-alpine@sha256:{SHA}"
+        assert pull_tag is None
+
+    def test_full_flow_ghcr(self) -> None:
+        """Test parse_repository_tag -> build_pull_arguments for GHCR."""
+        from ansible_collections.community.docker.plugins.module_utils._api.utils.utils import (
+            parse_repository_tag,
+        )
+
+        # User specifies: ghcr.io/gethomepage/homepage:v1.7@sha256:abc...
+        image_ref = f"ghcr.io/gethomepage/homepage:v1.7@sha256:{SHA}"
+        repo, tag = parse_repository_tag(image_ref)
+
+        assert repo == "ghcr.io/gethomepage/homepage"
+        assert tag == f"v1.7@sha256:{SHA}"
+
+        pull_name, pull_tag = build_pull_arguments(repo, tag)
+        assert pull_name == f"ghcr.io/gethomepage/homepage:v1.7@sha256:{SHA}"
+        assert pull_tag is None
+
+    def test_full_flow_private_registry_with_port(self) -> None:
+        """Test full flow for private registry with port number."""
+        from ansible_collections.community.docker.plugins.module_utils._api.utils.utils import (
+            parse_repository_tag,
+        )
+
+        # User specifies: localhost:5000/myapp:v2.0@sha256:abc...
+        image_ref = f"localhost:5000/myapp:v2.0@sha256:{SHA}"
+        repo, tag = parse_repository_tag(image_ref)
+
+        # Port should be part of repo, not confused with tag
+        assert repo == "localhost:5000/myapp"
+        assert tag == f"v2.0@sha256:{SHA}"
+
+        pull_name, pull_tag = build_pull_arguments(repo, tag)
+        assert pull_name == f"localhost:5000/myapp:v2.0@sha256:{SHA}"
+        assert pull_tag is None
+
+    def test_full_flow_tag_only(self) -> None:
+        """Test full flow for tag-only (no digest)."""
+        from ansible_collections.community.docker.plugins.module_utils._api.utils.utils import (
+            parse_repository_tag,
+        )
+
+        image_ref = "nginx:1.21"
+        repo, tag = parse_repository_tag(image_ref)
+
+        assert repo == "nginx"
+        assert tag == "1.21"
+
+        pull_name, pull_tag = build_pull_arguments(repo, tag)
+        assert pull_name == "nginx"
+        assert pull_tag == "1.21"
+
+    def test_full_flow_digest_only(self) -> None:
+        """Test full flow for digest-only (no tag)."""
+        from ansible_collections.community.docker.plugins.module_utils._api.utils.utils import (
+            parse_repository_tag,
+        )
+
+        image_ref = f"nginx@sha256:{SHA}"
+        repo, tag = parse_repository_tag(image_ref)
+
+        assert repo == "nginx"
+        assert tag == f"sha256:{SHA}"
+
+        pull_name, pull_tag = build_pull_arguments(repo, tag)
+        assert pull_name == "nginx"
+        assert pull_tag == f"sha256:{SHA}"