many: support the use of build-aux/snap

snapcraft/cli/lifecycle.py

@@ -82,7 +82,6 @@ def _install_multipass():
 
 
 # TODO: when snap is a real step we can simplify the arguments here.
-# fmt: off
 def _execute(  # noqa: C901
     step: steps.Step,
     parts: str,
@@ -93,22 +92,33 @@ def _execute(  # noqa: C901
     destructive_mode: bool = False,
     **kwargs
 ) -> "Project":
-    # fmt: on
     _clean_provider_error()
     provider = "host" if destructive_mode else None
     build_environment = env.BuilderEnvironmentConfig(force_provider=provider)
     try:
         conduct_build_environment_sanity_check(build_environment.provider)
     except MultipassMissingInstallableError as e:
-        click.echo("You need multipass installed to build snaps "
-                   "(https://github.com/CanonicalLtd/multipass).")
+        click.echo(
+            "You need multipass installed to build snaps "
+            "(https://github.com/CanonicalLtd/multipass)."
+        )
         if click.confirm("Would you like to install it now?"):
             _install_multipass()
         else:
-            raise errors.SnapcraftEnvironmentError("multipass is required to continue.") from e
+            raise errors.SnapcraftEnvironmentError(
+                "multipass is required to continue."
+            ) from e
 
     project = get_project(is_managed_host=build_environment.is_managed_host, **kwargs)
 
+    echo.wrapped(
+        "Using {!r}: Project assets will be "
+        "searched for from the {!r} directory.".format(
+            project.info.snapcraft_yaml_file_path,
+            os.path.relpath(project._get_snapcraft_assets_dir(), project._project_dir),
+        )
+    )
+
     conduct_project_sanity_check(project)
 
     if build_environment.is_managed_host or build_environment.is_host:
@@ -146,8 +156,10 @@ def _execute(  # noqa: C901
                 if project.debug:
                     instance.shell()
                 else:
-                    echo.warning("Run the same command again with --debug to shell into the environment "
-                                 "if you wish to introspect this failure.")
+                    echo.warning(
+                        "Run the same command again with --debug to shell into the environment "
+                        "if you wish to introspect this failure."
+                    )
                     raise
             else:
                 if shell or shell_after:
@@ -187,8 +199,10 @@ def init():
     """Initialize a snapcraft project."""
     snapcraft_yaml_path = lifecycle.init()
     echo.info("Created {}.".format(snapcraft_yaml_path))
-    echo.wrapped("Go to https://docs.snapcraft.io/the-snapcraft-format/8337 for more "
-                 "information about the snapcraft.yaml format.")
+    echo.wrapped(
+        "Go to https://docs.snapcraft.io/the-snapcraft-format/8337 for more "
+        "information about the snapcraft.yaml format."
+    )
 
 
 @lifecyclecli.command()

snapcraft/internal/meta/_snap_packaging.py

@@ -435,29 +435,41 @@ def _record_manifest_and_source_snapcraft_yaml(self):
     def write_snap_directory(self) -> None:
         # First migrate the snap directory. It will overwrite any conflicting
         # files.
-        for root, directories, files in os.walk("snap"):
+        for root, directories, files in os.walk(
+            self._project_config.project._get_snapcraft_assets_dir()
+        ):
             with contextlib.suppress(ValueError):
                 directories.remove(".snapcraft")
             with contextlib.suppress(ValueError):
                 # The snapcraft.yaml is migrated later
                 files.remove("snapcraft.yaml")
 
             for directory in directories:
-                source = os.path.join(root, directory)
-                destination = os.path.join(self._prime_dir, source)
+                source = os.path.relpath(
+                    os.path.join(root, directory),
+                    self._project_config.project._work_dir,
+                )
+                # Also build-aux from destination
+                destination = os.path.join(self._prime_dir, source.lstrip("build-aux/"))
                 file_utils.create_similar_directory(source, destination)
 
             for file_path in files:
-                source = os.path.join(root, file_path)
-                destination = os.path.join(self._prime_dir, source)
+                source = os.path.relpath(
+                    os.path.join(root, file_path),
+                    self._project_config.project._work_dir,
+                )
+                # Also build-aux from destination
+                destination = os.path.join(self._prime_dir, source.lstrip("build-aux/"))
                 with contextlib.suppress(FileNotFoundError):
                     os.remove(destination)
                 file_utils.link_or_copy(source, destination)
 
         # Now copy the assets contained within the snap directory directly into
         # meta.
         for origin in ["gui", "hooks"]:
-            src_dir = os.path.join("snap", origin)
+            src_dir = os.path.join(
+                self._project_config.project._get_snapcraft_assets_dir(), origin
+            )
             dst_dir = os.path.join(self.meta_dir, origin)
             if os.path.isdir(src_dir):
                 os.makedirs(dst_dir, exist_ok=True)

snapcraft/project/_get_snapcraft.py

@@ -22,6 +22,7 @@
 def get_snapcraft_yaml(base_dir=None):
     possible_yamls = [
         os.path.join("snap", "snapcraft.yaml"),
+        os.path.join("build-aux", "snap", "snapcraft.yaml"),
         "snapcraft.yaml",
         ".snapcraft.yaml",
     ]

snapcraft/project/_project.py

@@ -53,6 +53,14 @@ def __init__(
 
         super().__init__(target_deb_arch, debug, work_dir=work_dir)
 
+    def _get_snapcraft_assets_dir(self) -> str:
+        if self.info.snapcraft_yaml_file_path.endswith(
+            os.path.join("build-aux", "snap", "snapcraft.yaml")
+        ):
+            return os.path.join(self._project_dir, "build-aux", "snap")
+        else:
+            return os.path.join(self._project_dir, "snap")
+
     def _get_global_state_file_path(self) -> str:
         if self._is_managed_host:
             state_file_path = os.path.join(self._work_dir, "state")

tests/spread/general/build-aux/task.yaml

@@ -0,0 +1,42 @@
+summary: Use build-aux for snapcraft assets
+
+# We currently only have core18 on a stable channel
+systems: [ubuntu-18*]
+
+environment:
+  SNAPCRAFT_BUILD_INFO: on
+
+prepare: |
+  mkdir test-snap
+  cd test-snap
+  snapcraft init
+  mkdir snap/hooks
+  touch snap/hooks/install
+  mkdir snap/gui
+  touch snap/gui/icon.png
+
+  mkdir build-aux
+  mv snap build-aux
+
+restore: |
+  rm -rf test-snap
+
+execute: |
+  cd test-snap
+
+  snapcraft prime
+
+  if [ ! -f prime/meta/gui/icon.png ]; then
+      echo "Missing expected snap icon"
+      exit 1
+  fi
+
+  if [ ! -f prime/meta/hooks/install ]; then
+      echo "Missing expected snap install hook"
+      exit 1
+  fi
+
+  if [ ! -f prime/snap/snapcraft.yaml ]; then
+      echo "Missing snapcraft.yaml in snap dir"
+      exit 1
+  fi

tests/unit/project/test_get_snapcraft.py

@@ -27,6 +27,10 @@ class GetSnapcraftYamlTest(unit.TestCase):
     scenarios = [
         ("snapcraft.yaml", dict(file_path="snapcraft.yaml")),
         ("snap/snapcraft.yaml", dict(file_path=os.path.join("snap", "snapcraft.yaml"))),
+        (
+            "build-aux",
+            dict(file_path=os.path.join("build-aux", "snap", "snapcraft.yaml")),
+        ),
         (".snapcraft.yaml", dict(file_path=".snapcraft.yaml")),
     ]
 
@@ -65,6 +69,13 @@ class GetSnapcraftYamlDuplicateErrorsTest(unit.TestCase):
                 file_path2=os.path.join("snap", "snapcraft.yaml"),
             ),
         ),
+        (
+            "build-aux and snap",
+            dict(
+                file_path1=os.path.join("build-aux", "snap", "snapcraft.yaml"),
+                file_path2=os.path.join("snap", "snapcraft.yaml"),
+            ),
+        ),
     ]
 
     def test_duplicates(self):