bitbake: command: add error to return of runCommand

Currently, command.py can return an error message from runCommand, due to
being unable to run the command, yet few of our UIs (just hob) can handle it
today. This can result in seeing a TypeError with traceback in certain rare
circumstances.

To resolve this, we need a clean way to get errors back from runCommand,
without having to isinstance() the return value. This implements such a thing
by making runCommand also return an error (or None if no error occurred).

As runCommand now has a method of returning errors, we can also alter the
getCmdLineAction bits such that the returned value is just the action, not an
additional message. If a sync command wants to return an error, it raises
CommandError(message), and the message will be passed to the caller
appropriately.

Example Usage:

    result, error = server.runCommand(...)
    if error:
        log.error('Unable to run command: %s' % error)
        return 1

(Bitbake rev: 717831b8315cb3904d9b590e633000bc897e8fb6)

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/command.py

@@ -44,6 +44,9 @@ class CommandFailed(CommandExit):
         self.error = message
         CommandExit.__init__(self, 1)
 
+class CommandError(Exception):
+    pass
+
 class Command:
     """
     A queue of asynchronous commands for bitbake
@@ -57,21 +60,25 @@ class Command:
         self.currentAsyncCommand = None
 
     def runCommand(self, commandline):
-        try:
-            command = commandline.pop(0)
-            if command in CommandsSync.__dict__:
-                # Can run synchronous commands straight away
-                return getattr(CommandsSync, command)(self.cmds_sync, self, commandline)
-            if self.currentAsyncCommand is not None:
-                return "Busy (%s in progress)" % self.currentAsyncCommand[0]
-            if command not in CommandsAsync.__dict__:
-                return "No such command"
-            self.currentAsyncCommand = (command, commandline)
-            self.cooker.server_registration_cb(self.cooker.runCommands, self.cooker)
-            return True
-        except:
-            import traceback
-            return traceback.format_exc()
+        command = commandline.pop(0)
+        if hasattr(CommandsSync, command):
+            # Can run synchronous commands straight away
+            command_method = getattr(self.cmds_sync, command)
+            try:
+                result = command_method(self, commandline)
+            except CommandError as exc:
+                return None, exc.args[0]
+            except Exception:
+                return None, traceback.format_exc()
+            else:
+                return result, None
+        if self.currentAsyncCommand is not None:
+            return None, "Busy (%s in progress)" % self.currentAsyncCommand[0]
+        if command not in CommandsAsync.__dict__:
+            return None, "No such command"
+        self.currentAsyncCommand = (command, commandline)
+        self.cooker.server_registration_cb(self.cooker.runCommands, self.cooker)
+        return True, None
 
     def runAsyncCommand(self):
         try:
@@ -139,7 +146,11 @@ class CommandsSync:
         """
         Get any command parsed from the commandline
         """
-        return command.cooker.commandlineAction
+        cmd_action = command.cooker.commandlineAction
+        if cmd_action['msg']:
+            raise CommandError(msg)
+        else:
+            return cmd_action['action']
 
     def getVariable(self, command, params):
         """