Add the option to only show the configuration for a single project

esmvalcore/_main.py

@@ -178,14 +178,20 @@ def __init__(self) -> None:
     def show(
         self,
         filter: tuple[str] | None = ("extra_facets",),  # noqa: A002
+        project: str | None = None,
     ) -> None:
         """Show the current configuration.
 
         Parameters
         ----------
         filter:
             Filter this list of keys. By default, the `extra_facets`
-            key is filtered out, as it can be very large.
+            key is filtered out, as it can be very large. For example, to show
+            the full configuration, use `--filter=` and to filter out both
+            the `data` and `extra_facets` keys use `--filter=data,extra_facets`.
+        project:
+            Only show configuration for this project. For example, to only show
+            the configuration for the CMIP7 project, use `--project=CMIP7`.
 
         """
         import yaml
@@ -195,15 +201,19 @@ def show(
         from esmvalcore.config import CFG
 
         cfg = dict(CFG)
+        msg = "# Current configuration"
+        if project and "projects" in cfg and project in cfg["projects"]:
+            cfg = {"projects": {project: cfg["projects"][project]}}
+            msg += f" for project '{project}'"
         if filter:
+            if isinstance(filter, str):
+                filter = (filter,)  # noqa: A001
             for key in filter:
                 cfg = nested_delete(cfg, key)
-        exclude_msg = (
-            ", excluding the keys " + ", ".join(f"'{f}'" for f in filter)
-            if filter
-            else ""
-        )
-        self.console.print(f"# Current configuration{exclude_msg}:")
+            msg += ", excluding the keys " + ", ".join(
+                f"'{key}'" for key in filter
+            )
+        self.console.print(f"{msg}:")
         self.console.print(
             Syntax(
                 yaml.safe_dump(cfg),

tests/integration/test_main.py

@@ -205,7 +205,7 @@ def test_config_show(
     cfg_default: Config,
 ) -> None:
     """Test esmvaltool config show command."""
-    with arguments("esmvaltool", "config", "show", "--filter=None"):
+    with arguments("esmvaltool", "config", "show", "--filter="):
         run()
     stdout = capsys.readouterr().out
     expected_header = "# Current configuration:\n"
@@ -216,6 +216,41 @@ def test_config_show(
     assert cfg == reference
 
 
+def test_config_show_single_project(
+    capsys: pytest.CaptureFixture,
+    cfg_default: Config,
+) -> None:
+    """Test esmvaltool config show command for a single project."""
+    with arguments("esmvaltool", "config", "show", "--project=CMIP7"):
+        run()
+    stdout = capsys.readouterr().out
+    expected_header = "# Current configuration for project 'CMIP7', excluding the keys 'extra_facets':\n"
+    assert expected_header in stdout
+    cfg_txt = stdout.split(expected_header)[1]
+    cfg = yaml.safe_load(cfg_txt)
+    assert "projects" in cfg
+    assert "CMIP7" in cfg["projects"]
+    assert "CMIP6" not in cfg["projects"]
+
+
+def test_config_show_filter(
+    capsys: pytest.CaptureFixture,
+    cfg_default: Config,
+) -> None:
+    """Test esmvaltool config show command for a single project."""
+    with arguments("esmvaltool", "config", "show", "--filter=projects"):
+        run()
+    stdout = capsys.readouterr().out
+    expected_header = (
+        "# Current configuration, excluding the keys 'projects':\n"
+    )
+    assert expected_header in stdout
+    cfg_txt = stdout.split(expected_header)[1]
+    cfg = yaml.safe_load(cfg_txt)
+    assert cfg
+    assert "projects" not in cfg
+
+
 def test_config_show_brief_by_default(capsys: pytest.CaptureFixture) -> None:
     """Test that the `esmvaltool config show` command produces readable results."""
     with arguments("esmvaltool", "config", "show"):