Allow build to be skipped

test/data/my-environment.yml

@@ -0,0 +1,5 @@
+name: xcengine
+channels:
+  - conda-forge
+dependencies:
+  - python >=3.11

test/test_cli.py

@@ -1,3 +1,4 @@
+import pathlib
 import re
 import urllib
 from unittest.mock import patch, ANY, MagicMock
@@ -86,7 +87,7 @@ def test_image_build(builder_mock, tmp_path, specify_dir, specify_env):
         tag=tag,
         build_dir=(build_dir if specify_dir else ANY),
     )
-    instance_mock.build.assert_called_once_with()
+    instance_mock.build.assert_called_once_with(skip_build=False)
 
 
 @patch("xcengine.cli.ContainerRunner")
@@ -180,3 +181,25 @@ def urlopen(url):
     assert count == 2
     assert passed_url == f"http://localhost:{port}"
     open_mock.assert_called_once_with(f"http://localhost:{port}/viewer")
+
+@patch("docker.from_env")
+def test_image_skip_build_save_dockerfile_and_env(from_env_mock, tmp_path):
+    build_dir = tmp_path / "build"
+    nb_path = pathlib.Path(__file__).parent / "data" / "noparamtest.ipynb"
+    cli_runner = CliRunner()
+    result = cli_runner.invoke(
+        cli,
+        [
+            "image",
+            "build",
+            "--skip-build",
+            "--build-dir",
+            str(build_dir),
+            str(nb_path),
+        ],
+    )
+    assert result.exit_code == 0
+    assert (build_dir / "Dockerfile").is_file()
+    assert (build_dir / "environment.yml").is_file()
+    from_env_mock.assert_not_called()
+

test/test_core.py

@@ -330,3 +330,31 @@ def test_image_builder_notebook_config(tmp_path):
     config = image_builder.script_creator.nb_params.config
     assert config["environment_file"] == "my-environment.yml"
     assert config["container_image_tag"] == "my-tag"
+
+
+def test_image_builder_write_dockerfile(tmp_path):
+    ImageBuilder.write_dockerfile(
+        dockerfilepath := tmp_path / "as-yet-nonexistent-dir" / "Dockerfile"
+    )
+    with open(dockerfilepath) as fh:
+        content = fh.read()
+        assert content.startswith("FROM ")
+        assert "\nENTRYPOINT " in content
+
+
+@patch("docker.from_env")
+def test_image_builder_build_skip_build(from_env_mock, tmp_path):
+    build_dir = tmp_path / "build"
+    image_builder = ImageBuilder(
+        pathlib.Path(__file__).parent / "data" / "noparamtest.ipynb",
+        None,
+        build_dir,
+        None,
+    )
+    image_builder.build(skip_build=True)
+    from_env_mock.assert_not_called()
+    env_path = build_dir / "environment.yml"
+    assert env_path.is_file()
+    with open(env_path) as fh:
+        env_dict = yaml.safe_load(fh)
+        assert {"name", "channels", "dependencies"} <= set(env_dict)

xcengine/cli.py

@@ -146,13 +146,21 @@ def image_cli():
     help="Write a CWL file defining an Earth Observation Application Package "
     "to the specified path.",
 )
+@click.option(
+    "-s",
+    "--skip-build",
+    is_flag=True,
+    help="Prepare the Dockerfile and build context, but don't actually build "
+    "the image"
+)
 @notebook_argument
 def build(
     build_dir: pathlib.Path,
     notebook: pathlib.Path,
     environment: pathlib.Path,
     tag: str,
     eoap: pathlib.Path,
+    skip_build: bool
 ) -> None:
     if environment is None:
         LOGGER.info("No environment file specified on command line.")
@@ -166,13 +174,13 @@ class InitArgs(TypedDict):
     if build_dir:
         image_builder = ImageBuilder(build_dir=build_dir, **init_args)
         os.makedirs(build_dir, exist_ok=True)
-        image = image_builder.build()
+        image = image_builder.build(skip_build=skip_build)
     else:
         with tempfile.TemporaryDirectory() as temp_dir:
             image_builder = ImageBuilder(
                 build_dir=pathlib.Path(temp_dir), **init_args
             )
-            image = image_builder.build()
+            image = image_builder.build(skip_build=skip_build)
     if eoap:
 
         class IndentDumper(yaml.Dumper):
@@ -186,7 +194,11 @@ def increase_indent(self, flow=False, indentless=False):
                 Dumper=IndentDumper,
             )
         )
-    print(f"Built image with tags {image.tags}")
+    print(
+        f"Built image with tags {image.tags}"
+        if image is not None else
+        "No image built"
+    )
 
 
 @image_cli.command(
@@ -233,7 +245,7 @@ def increase_indent(self, flow=False, indentless=False):
     help="Keep container after it has finished running.",
 )
 @click.option(
-    "-b",
+    "-w",
     "--open-browser",
     is_flag=True,
     help="After the server has started, open a web browser window "

xcengine/core.py

@@ -231,7 +231,10 @@ def __init__(
                     LOGGER.info(f"No environment found at {notebook_sibling}")
                     self.environment = None
 
-    def build(self) -> Image:
+    def build(
+        self,
+        skip_build: bool = False,
+    ) -> Image | None:
         self.script_creator.convert_notebook_to_script(self.build_dir)
         if self.environment:
             with open(self.environment, "r") as fh:
@@ -247,7 +250,8 @@ def build(self) -> Image:
         self.add_packages_to_environment(env_def, ["xcube", "pystac"])
         with open(self.build_dir / "environment.yml", "w") as fh:
             fh.write(yaml.safe_dump(env_def))
-        return self._build_image()
+        self.write_dockerfile(self.build_dir / "Dockerfile")
+        return None if skip_build else self._build_image()
 
     @staticmethod
     def export_conda_env() -> dict:
@@ -308,22 +312,6 @@ def ensure_present(pkg: str):
 
     def _build_image(self) -> docker.models.images.Image:
         client = docker.from_env()
-        dockerfile = textwrap.dedent("""
-        FROM mambaorg/micromamba:1.5.10-noble-cuda-12.6.0
-        COPY Dockerfile Dockerfile
-        COPY environment.yml environment.yml
-        RUN micromamba install -y -n base -f environment.yml && \
-        micromamba clean --all --yes
-        WORKDIR /home/mambauser
-        COPY user_code.py user_code.py
-        COPY execute.py execute.py
-        COPY parameters.yaml parameters.yaml
-        COPY parameters.py parameters.py
-        COPY util.py util.py
-        ENTRYPOINT ["/usr/local/bin/_entrypoint.sh", "python", "/home/mambauser/execute.py"]
-        """)
-        with open(self.build_dir / "Dockerfile", "w") as fh:
-            fh.write(dockerfile)
         LOGGER.info(f"Building image with tag {self.tag}...")
         try:
             image, logs = client.images.build(
@@ -338,6 +326,30 @@ def _build_image(self) -> docker.models.images.Image:
         LOGGER.info("Docker image built.")
         return image
 
+    @staticmethod
+    def write_dockerfile(destination: pathlib.Path) -> None:
+        LOGGER.info(f"Writing Dockerfile to {destination}...")
+        destination.parent.mkdir(parents=True, exist_ok=True)
+        with open(destination, "w") as fh:
+            fh.write(textwrap.dedent("""\
+            FROM mambaorg/micromamba:1.5.10-noble-cuda-12.6.0
+            COPY Dockerfile Dockerfile
+            COPY environment.yml environment.yml
+            RUN micromamba install -y -n base -f environment.yml && \\
+              micromamba clean --all --yes
+            WORKDIR /home/mambauser
+            COPY user_code.py user_code.py
+            COPY execute.py execute.py
+            COPY parameters.yaml parameters.yaml
+            COPY parameters.py parameters.py
+            COPY util.py util.py
+            ENTRYPOINT [ \\
+              "/usr/local/bin/_entrypoint.sh", \\
+              "python", \\
+              "/home/mambauser/execute.py" \\
+            ]
+            """))
+
     def create_cwl(self):
         return self.script_creator.create_cwl(self.tag)