feat: reactive support for 26.04

charmcraft/application/main.py

@@ -130,12 +130,11 @@ def _get_app_plugins(self) -> dict[str, PluginType]:
             )
         except ProjectFileMissingError:
             return plugins
-        bases = {build_info.build_base for build_info in full_build_plan}
-        for base in bases:
-            if str(base) not in const.CHARM_OR_REACTIVE_BASES:
-                plugins.pop("charm")
-                plugins.pop("reactive")
-                break
+        bases = {str(build_info.build_base) for build_info in full_build_plan}
+        if any(base not in const.CHARM_PLUGIN_BASES for base in bases):
+            plugins.pop("charm", None)
+        if any(base not in const.REACTIVE_PLUGIN_BASES for base in bases):
+            plugins.pop("reactive", None)
 
         return plugins
 

charmcraft/const.py

@@ -62,7 +62,7 @@
     "almalinux@9",
 )
 
-CHARM_OR_REACTIVE_BASES = frozenset(  # Bases with the 'charm' & 'reactive' plugins.
+CHARM_PLUGIN_BASES = frozenset(  # Bases with the 'charm' plugin.
     (
         *LEGACY_BASES,
         "ubuntu@24.04",
@@ -71,30 +71,45 @@
     )
 )
 
+REACTIVE_PLUGIN_BASES = frozenset(  # Bases with the 'reactive' plugin.
+    (
+        *CHARM_PLUGIN_BASES,
+        "ubuntu@26.04",
+    )
+)
+
 CommonBaseStr = Literal[  # Bases supported as both build bases and run bases
     "ubuntu@18.04",
     "ubuntu@20.04",
     "ubuntu@22.04",
     "ubuntu@24.04",
     "ubuntu@25.04",
     "ubuntu@25.10",
+    "ubuntu@26.04",
     "almalinux@9",
 ]
-BaseStr = CommonBaseStr | Literal["ubuntu@26.04"]
+BaseStr = CommonBaseStr
 BuildBaseStr = CommonBaseStr | Literal["ubuntu@devel"]
 
 DEVEL_BASE_STRINGS = (
     "ubuntu@25.04",
     "ubuntu@25.10",
-    "ubuntu@26.04",
 )  # Bases that require a specified build base.
 
 SUPPORTED_BASE_STRINGS = frozenset(
     # Bases that do not need a specific "devel" build base.
     (
         *(
             f"ubuntu@{series}"
-            for series in ("18.04", "20.04", "22.04", "24.04", "25.04", "25.10")
+            for series in (
+                "18.04",
+                "20.04",
+                "22.04",
+                "24.04",
+                "25.04",
+                "25.10",
+                "26.04",
+            )
         ),
         *(("almalinux@9",)),
     )

charmcraft/models/project.py

@@ -236,6 +236,11 @@ def started_at(self) -> datetime.datetime:
         """Get the time that Charmcraft started running."""
         return self._started_at
 
+    @classmethod
+    def _get_devel_bases(cls) -> Iterable[Any]:
+        """Return craft-application devel bases that require build-base: devel."""
+        return ()
+
     @classmethod
     def unmarshal(cls, data: dict[str, Any]):
         """Create a Charmcraft project from a dictionary of data."""
@@ -927,27 +932,27 @@ def _populate_platforms(cls, platforms: dict[str, Any]) -> dict[str, Any]:
     def _validate_removed_questing_plugins(
         cls, value: dict[str, dict[str, Any]], info: pydantic.ValidationInfo
     ) -> dict[str, dict[str, Any]]:
-        """Check that the charm and reactive plugins aren't used on Ubuntu 25.10+."""
+        """Check that the charm and reactive plugins are only used on supported bases."""
         plugins = {v.get("plugin", k) for k, v in value.items()}
-        if not plugins & {"charm", "reactive"}:
+        legacy_plugins = plugins & {"charm", "reactive"}
+        if not legacy_plugins:
             return value
-        if (base := info.data.get("base")) in const.CHARM_OR_REACTIVE_BASES:
-            return value
-        if base is not None:
-            raise ValueError(
-                f"Cannot use 'charm' or 'reactive' plugins with base {base!r}"
-            )
-        # Multi-base charms.
-        build_bases = {
-            str(info.build_base)
-            for info in craft_platforms.charm.get_platforms_charm_build_plan(
-                base=None,
-                platforms=pydantic.TypeAdapter(PlatformsDict).dump_python(
-                    info.data["platforms"], mode="json", by_alias=True
-                ),
-            )
-        }
-        if invalid_bases := build_bases - const.CHARM_OR_REACTIVE_BASES:
+
+        if base := info.data.get("base"):
+            build_bases = {base}
+        else:
+            # Multi-base charms.
+            build_bases = {
+                str(info.build_base)
+                for info in craft_platforms.charm.get_platforms_charm_build_plan(
+                    base=None,
+                    platforms=pydantic.TypeAdapter(PlatformsDict).dump_python(
+                        info.data["platforms"], mode="json", by_alias=True
+                    ),
+                )
+            }
+
+        if invalid_bases := build_bases - const.REACTIVE_PLUGIN_BASES:
             if len(invalid_bases) == 1:
                 raise ValueError(
                     f"Cannot use 'charm' or 'reactive' plugins with base {invalid_bases.pop()!r}"
@@ -956,6 +961,19 @@ def _validate_removed_questing_plugins(
             raise ValueError(
                 f"Cannot use 'charm' or 'reactive' plugins with bases {invalid_bases_str}"
             )
+
+        if "charm" in legacy_plugins:
+            if invalid_bases := build_bases - const.CHARM_PLUGIN_BASES:
+                if len(invalid_bases) == 1:
+                    raise ValueError(
+                        f"Cannot use 'charm' plugin with base {invalid_bases.pop()!r}"
+                    )
+                invalid_bases_str = humanize_list(
+                    sorted(invalid_bases), conjunction="or"
+                )
+                raise ValueError(
+                    f"Cannot use 'charm' plugin with bases {invalid_bases_str}"
+                )
         return value
 
 

charmcraft/parts/plugins/_reactive.py

@@ -103,7 +103,14 @@ def get_build_snaps(cls) -> set[str]:
 
     def get_build_packages(self) -> set[str]:
         """Return a set of required packages to install in the build environment."""
-        return set()
+        return {
+            "git",
+            "python3-pip",
+            "python3-setuptools",
+            "python3-venv",
+            "python3-wheel",
+            "virtualenv",
+        }
 
     def get_build_environment(self) -> dict[str, str]:
         """Return a dictionary with the environment to use in the build step."""

pyproject.toml

@@ -8,7 +8,7 @@ dependencies = [
     "craft-cli>=2.15.0",
     "craft-grammar>=2.0.0",
     "craft-parts~=2.20",
-    "craft-providers~=3.1",
+    "craft-providers>=3.4.0,<4.0",
     "craft-platforms~=0.10",
     "craft-store~=3.2",
     "distro>=1.7.0",

schema/charmcraft.json

@@ -900,14 +900,11 @@
 								"ubuntu@24.04",
 								"ubuntu@25.04",
 								"ubuntu@25.10",
+								"ubuntu@26.04",
 								"almalinux@9"
 							],
 							"type": "string"
 						},
-						{
-							"const": "ubuntu@26.04",
-							"type": "string"
-						},
 						{
 							"type": "null"
 						}
@@ -925,6 +922,7 @@
 								"ubuntu@24.04",
 								"ubuntu@25.04",
 								"ubuntu@25.10",
+								"ubuntu@26.04",
 								"almalinux@9"
 							],
 							"type": "string"

tests/integration/invalid-charms/multibase-charm-plugin/errors.json

@@ -4,15 +4,15 @@
     "loc": [
       "parts"
     ],
-    "msg": "Value error, Cannot use 'charm' or 'reactive' plugins with bases 'ubuntu@25.10' or 'ubuntu@26.04'",
+    "msg": "Value error, Cannot use 'charm' or 'reactive' plugins with base 'ubuntu@25.10'",
     "input": {
       "my-part": {
         "plugin": "charm",
         "source": "."
       }
     },
     "ctx": {
-      "error": "Cannot use 'charm' or 'reactive' plugins with bases 'ubuntu@25.10' or 'ubuntu@26.04'"
+      "error": "Cannot use 'charm' or 'reactive' plugins with base 'ubuntu@25.10'"
     }
   }
 ]

tests/integration/invalid-charms/multibase-resolute-charm-plugin/charmcraft.yaml

@@ -1,13 +1,12 @@
-type: charm
-name: test-charm
+name: invalid-charm
 summary: An invalid charm based on Ubuntu Resolute (26.04 LTS) with the charm plugin.
-description: test-charm
-
+description: |
+  Charm plugin is not supported on Ubuntu 26.04 LTS.
+type: charm
 platforms:
-  "resolute":
+  resolute:
     build-on: ubuntu@26.04:amd64
     build-for: ubuntu@26.04:amd64
-
 parts:
   my-part:
     plugin: charm

tests/integration/invalid-charms/multibase-resolute-charm-plugin/errors.json

@@ -4,15 +4,15 @@
     "loc": [
       "parts"
     ],
-    "msg": "Value error, Cannot use 'charm' or 'reactive' plugins with base 'ubuntu@26.04'",
+    "msg": "Value error, Cannot use 'charm' plugin with base 'ubuntu@26.04'",
     "input": {
       "my-part": {
         "plugin": "charm",
         "source": "."
       }
     },
     "ctx": {
-      "error": "Cannot use 'charm' or 'reactive' plugins with base 'ubuntu@26.04'"
+      "error": "Cannot use 'charm' plugin with base 'ubuntu@26.04'"
     }
   }
 ]

tests/integration/invalid-charms/resolute-charm-plugin/charmcraft.yaml

@@ -1,15 +1,11 @@
-type: charm
-name: test-charm
+name: invalid-charm
 summary: An invalid charm based on Ubuntu Resolute (26.04 LTS) with the charm plugin.
-description: test-charm
-
+description: |
+  Charm plugin is not supported on Ubuntu 26.04 LTS.
+type: charm
 base: ubuntu@26.04
-build-base: ubuntu@devel
 platforms:
   amd64:
-  arm64:
-  riscv64:
-
 parts:
   my-part:
     plugin: charm

tests/integration/invalid-charms/resolute-charm-plugin/errors.json

@@ -4,15 +4,15 @@
     "loc": [
       "parts"
     ],
-    "msg": "Value error, Cannot use 'charm' or 'reactive' plugins with base 'ubuntu@26.04'",
+    "msg": "Value error, Cannot use 'charm' plugin with base 'ubuntu@26.04'",
     "input": {
       "my-part": {
         "plugin": "charm",
         "source": "."
       }
     },
     "ctx": {
-      "error": "Cannot use 'charm' or 'reactive' plugins with base 'ubuntu@26.04'"
+      "error": "Cannot use 'charm' plugin with base 'ubuntu@26.04'"
     }
   }
 ]

tests/integration/sample-charms/platforms-resolute-reactive/charmcraft.yaml

@@ -0,0 +1,12 @@
+name: example-charm
+summary: An example charm with platforms
+description: |
+  A description for an example charm with platforms.
+type: charm
+base: ubuntu@26.04
+platforms:
+  amd64:
+
+parts:
+  reactive:
+    plugin: reactive

tests/integration/sample-charms/platforms-resolute-reactive/expected.yaml

@@ -0,0 +1,15 @@
+name: example-charm
+summary: An example charm with platforms
+description: |
+  A description for an example charm with platforms.
+base: ubuntu@26.04
+platforms:
+  amd64:
+    build-on:
+    - amd64
+    build-for:
+    - amd64
+parts:
+  reactive:
+    plugin: reactive
+type: charm

tests/integration/test_application.py

@@ -125,5 +125,12 @@ def test_remove_charm_reactive_plugins(
 
     with pytest.raises(ValueError, match="plugin not registered: 'charm'"):
         craft_parts.plugins.plugins.get_plugin_class("charm")
-    with pytest.raises(ValueError, match="plugin not registered: 'reactive'"):
+
+    if charm_dir.name in {
+        "multibase-resolute-charm-plugin",
+        "resolute-charm-plugin",
+    }:
         craft_parts.plugins.plugins.get_plugin_class("reactive")
+    else:
+        with pytest.raises(ValueError, match="plugin not registered: 'reactive'"):
+            craft_parts.plugins.plugins.get_plugin_class("reactive")

tests/spread/smoketests/reactive/reactivecharm/charmcraft.yaml

@@ -2,14 +2,19 @@ type: "charm"
 bases:
   - build-on:
       - name: "ubuntu"
-        channel: "22.04"
+        channel: "BASE_CHANNEL"
     run-on:
       - name: "ubuntu"
-        channel: "22.04"
+        channel: "BASE_CHANNEL"
 parts:
   charm:
     source: .
     plugin: reactive
+    reactive-charm-build-arguments:
+      - -v
+      - --binary-wheels-from-source
+      - --upgrade-buildvenv-core-deps
+      - --ignore-requires-python
     build-snaps:
       - charm/CHARM_SNAP_CHANNEL
     build-packages: [python3-dev]