commands: Show less generic error when no manifest is loaded

src/west/app/main.py

@@ -37,8 +37,8 @@
     SelfUpdate, ForAll, Init, Update, Topdir
 from west.app.config import Config
 from west.manifest import Manifest, MalformedConfig, MalformedManifest, \
-    ManifestVersionError, ManifestImportFailed, _ManifestImportDepth, \
-    ManifestProject, MANIFEST_REV_BRANCH
+    _ManifestRequired, ManifestVersionError, ManifestImportFailed, \
+    _ManifestImportDepth, ManifestProject, MANIFEST_REV_BRANCH
 from west.util import quote_sh_list, west_topdir, WestNotFound
 from west.version import __version__
 
@@ -608,9 +608,18 @@ def run_builtin(self, args, unknown):
             self.handle_builtin_manifest_load_err(args)
         for io_hook in self.queued_io:
             self.cmd.add_pre_run_hook(io_hook)
-        self.cmd.run(args, unknown, self.topdir,
-                     manifest=self.manifest,
-                     config=self.config)
+        try:
+            self.cmd.run(args, unknown, self.topdir,
+                         manifest=self.manifest,
+                         config=self.config)
+        except _ManifestRequired:
+            # We tried to run the command despite having failed to
+            # load_manifest(), but the manifest was needed after all.
+            # Show the deferred exception and exit.
+            if self.mle.args:
+                self.cmd.die('\n  '.join(str(arg) for arg in self.mle.args))
+            else:
+                self.cmd.die(str(self.mle))
 
     def run_extension(self, name, argv):
         # Check a program invariant. We should never get here

src/west/commands.py

@@ -25,7 +25,7 @@
 import yaml
 
 from west.configuration import Configuration
-from west.manifest import Manifest, Project
+from west.manifest import Manifest, _ManifestRequired, Project
 from west.util import escapes_directory, quote_sh_list, PathType
 
 '''\
@@ -258,9 +258,7 @@ def _get_manifest(self) -> Manifest:
         Otherwise, a fatal error occurs.
         '''
         if self._manifest is None:
-            self.die(f"can't run west {self.name};",
-                     "it requires the manifest, which was not available.",
-                     'Try "west manifest --validate" to debug.')
+            raise _ManifestRequired
         return self._manifest
 
     def _set_manifest(self, manifest: Optional[Manifest]):

src/west/manifest.py

@@ -685,6 +685,10 @@ class _ManifestImportDepth(ManifestImportFailed):
     # A hack to signal to main.py what happened.
     pass
 
+class _ManifestRequired(Exception):
+    # A built-in command had to read the manifest but it wasn't loaded.
+    pass
+
 #
 # The main Manifest class and its public helper types, like Project
 # and ImportFlag.