Fix volume mounts on user container (#931)

**Pull Request Checklist**
- [x] Fixes #930
- [x] Tests added
- [x] Documentation/examples added
- [x] [Good commit messages](https://cbea.ms/git-commit/) and/or PR
title

See #930

CC: @abschm

---------

Signed-off-by: Flaviu Vadan <flaviuvadan@gmail.com>

docs/examples/workflows/user_container.md

@@ -0,0 +1,67 @@
+# User Container
+
+
+
+This example showcases the user of a user container with a volume mount.
+
+
+=== "Hera"
+
+    ```python linenums="1"
+    from hera.workflows import (
+        DAG,
+        UserContainer,
+        Workflow,
+        models as m,
+        script,
+    )
+
+
+    @script(
+        sidecars=[
+            UserContainer(name="sidecar-name", volume_mounts=[m.VolumeMount(mount_path="/whatever", name="something")])
+        ]
+    )
+    def foo():
+        print("hi")
+
+
+    with Workflow(generate_name="sidecar-volume-mount-", entrypoint="d") as w:
+        with DAG(name="d"):
+            foo()
+    ```
+
+=== "YAML"
+
+    ```yaml linenums="1"
+    apiVersion: argoproj.io/v1alpha1
+    kind: Workflow
+    metadata:
+      generateName: sidecar-volume-mount-
+    spec:
+      entrypoint: d
+      templates:
+      - dag:
+          tasks:
+          - name: foo
+            template: foo
+        name: d
+      - name: foo
+        script:
+          command:
+          - python
+          image: python:3.8
+          source: 'import os
+
+            import sys
+
+            sys.path.append(os.getcwd())
+
+            print(''hi'')'
+        sidecars:
+        - name: sidecar-name
+          volumeMounts:
+          - mountPath: /whatever
+            name: something
+    ```
+

examples/workflows/upstream/title-and-descriptin-with-markdown.upstream.yaml

@@ -0,0 +1,19 @@
+apiVersion: argoproj.io/v1alpha1
+kind: Workflow
+metadata:
+  generateName: title-and-description-with-markdown-
+  labels:
+    workflows.argoproj.io/archive-strategy: "false"
+  annotations:
+    workflows.argoproj.io/title: "**Test Title**"
+    workflows.argoproj.io/description: |
+      `This is a simple hello world example.`
+      You can also run it in Python: https://couler-proj.github.io/couler/examples/#hello-world
+spec:
+  entrypoint: whalesay
+  templates:
+  - name: whalesay
+    container:
+      image: docker/whalesay:latest
+      command: [cowsay]
+      args: ["hello world"]

examples/workflows/user-container.yaml

@@ -0,0 +1,29 @@
+apiVersion: argoproj.io/v1alpha1
+kind: Workflow
+metadata:
+  generateName: sidecar-volume-mount-
+spec:
+  entrypoint: d
+  templates:
+  - dag:
+      tasks:
+      - name: foo
+        template: foo
+    name: d
+  - name: foo
+    script:
+      command:
+      - python
+      image: python:3.8
+      source: 'import os
+
+        import sys
+
+        sys.path.append(os.getcwd())
+
+        print(''hi'')'
+    sidecars:
+    - name: sidecar-name
+      volumeMounts:
+      - mountPath: /whatever
+        name: something

examples/workflows/user_container.py

@@ -0,0 +1,23 @@
+"""This example showcases the user of a user container with a volume mount."""
+
+from hera.workflows import (
+    DAG,
+    UserContainer,
+    Workflow,
+    models as m,
+    script,
+)
+
+
+@script(
+    sidecars=[
+        UserContainer(name="sidecar-name", volume_mounts=[m.VolumeMount(mount_path="/whatever", name="something")])
+    ]
+)
+def foo():
+    print("hi")
+
+
+with Workflow(generate_name="sidecar-volume-mount-", entrypoint="d") as w:
+    with DAG(name="d"):
+        foo()

src/hera/workflows/user_container.py

@@ -9,6 +9,7 @@
     ImagePullPolicy,
     ResourceRequirements,
     UserContainer as _ModelUserContainer,
+    VolumeMount as _ModelVolumeMount,
 )
 from hera.workflows.resources import Resources
 from hera.workflows.volume import _BaseVolume
@@ -49,6 +50,18 @@ def _build_image_pull_policy(self) -> Optional[str]:
                 "Use one of {ImagePullPolicy.__members__}"
             ) from e
 
+    def _build_volume_mounts(self) -> Optional[List[_ModelVolumeMount]]:
+        """Processes the volume mounts field and returns a generated `VolumeMount`."""
+        volume_mounts = self.volume_mounts
+        # extra volume mounts stem from using custom Hera volumes, which dynamically provision PVs + PVCs
+        extra_volume_mounts = None if self.volumes is None else [v._build_volume_mount() for v in self.volumes]
+        if volume_mounts is None:
+            volume_mounts = extra_volume_mounts
+        elif extra_volume_mounts is not None:
+            volume_mounts.extend(extra_volume_mounts)
+
+        return volume_mounts
+
     def build(self) -> _ModelUserContainer:
         """Builds the Hera auto-generated model of the user container."""
         env: List[EnvVar] = [
@@ -57,6 +70,7 @@ def build(self) -> _ModelUserContainer:
         env_from: List[EnvFromSource] = [
             var if isinstance(var, EnvFromSource) else cast(_BaseEnvFrom, var).build() for var in (self.env_from or [])
         ]
+
         return _ModelUserContainer(
             args=self.args,
             command=self.command,
@@ -83,7 +97,7 @@ def build(self) -> _ModelUserContainer:
             termination_message_policy=self.termination_message_policy,
             tty=self.tty,
             volume_devices=self.volume_devices,
-            volume_mounts=None if self.volumes is None else [v._build_volume_mount() for v in self.volumes],
+            volume_mounts=self._build_volume_mounts(),
             working_dir=self.working_dir,
         )
 

tests/test_unit/test_user_container.py

@@ -1,5 +1,10 @@
-from hera.workflows.models import ImagePullPolicy
+from hera.workflows.models import (
+    ImagePullPolicy,
+    UserContainer as ModelUserContainer,
+    VolumeMount,
+)
 from hera.workflows.user_container import UserContainer
+from hera.workflows.volume import Volume
 
 
 class TestUserContainer:
@@ -9,3 +14,35 @@ def test_build_image_pull_policy(self) -> None:
             UserContainer(name="test", image_pull_policy=ImagePullPolicy.always)._build_image_pull_policy() == "Always"
         )
         assert UserContainer(name="test")._build_image_pull_policy() is None
+
+    def test_builds_volume_mounts(self) -> None:
+        uc: ModelUserContainer = UserContainer(
+            name="test", volume_mounts=[VolumeMount(name="test", mount_path="/test")]
+        ).build()
+        assert isinstance(uc, ModelUserContainer)
+        assert uc.volume_mounts is not None
+        assert len(uc.volume_mounts) == 1
+        assert uc.volume_mounts[0].name == "test"
+        assert uc.volume_mounts[0].mount_path == "/test"
+
+        uc: ModelUserContainer = UserContainer(
+            name="test", volumes=[Volume(name="test", mount_path="/test", size="1Gi")]
+        ).build()
+        assert isinstance(uc, ModelUserContainer)
+        assert uc.volume_mounts is not None
+        assert len(uc.volume_mounts) == 1
+        assert uc.volume_mounts[0].name == "test"
+        assert uc.volume_mounts[0].mount_path == "/test"
+
+        uc: ModelUserContainer = UserContainer(
+            name="test",
+            volume_mounts=[VolumeMount(name="test1", mount_path="/test1")],
+            volumes=[Volume(name="test2", mount_path="/test2", size="1Gi")],
+        ).build()
+        assert isinstance(uc, ModelUserContainer)
+        assert uc.volume_mounts is not None
+        assert len(uc.volume_mounts) == 2
+        assert uc.volume_mounts[0].name == "test1"
+        assert uc.volume_mounts[0].mount_path == "/test1"
+        assert uc.volume_mounts[1].name == "test2"
+        assert uc.volume_mounts[1].mount_path == "/test2"