qapi: Split error.json off common.json

In my "build everything" tree, changing a type in qapi/common.json
triggers a recompile of some 3600 out of 6600 objects (not counting
tests and objects that don't depend on qemu/osdep.h).

One common dependency is QapiErrorClass: it's used only in in
qapi/error.h, which uses nothing else, and is widely included.

Move QapiErrorClass from common.json to new error.json.  Touching
common.json now recompiles only some 2900 objects.

Cc: Eric Blake <eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190812052359.30071-4-armbru@redhat.com>

MAINTAINERS

@@ -1874,6 +1874,7 @@ M: Markus Armbruster <armbru@redhat.com>
 S: Supported
 F: include/qapi/error.h
 F: include/qemu/error-report.h
+F: qapi/error.json
 F: util/error.c
 F: util/qemu-error.c
 
@@ -2062,6 +2063,7 @@ F: monitor/monitor-internal.h
 F: monitor/qmp*
 F: monitor/misc.c
 F: monitor/monitor.c
+F: qapi/error.json
 F: docs/devel/*qmp-*
 F: docs/interop/*qmp-*
 F: scripts/qmp/

include/qapi/error.h

@@ -119,7 +119,7 @@
 #ifndef ERROR_H
 #define ERROR_H
 
-#include "qapi/qapi-types-common.h"
+#include "qapi/qapi-types-error.h"
 
 /*
  * Overall category of an error.

qapi/Makefile.objs

@@ -6,7 +6,7 @@ util-obj-y += qmp-event.o
 util-obj-y += qapi-util.o
 
 QAPI_COMMON_MODULES = audio authz block-core block char common crypto
-QAPI_COMMON_MODULES += dump introspect job machine migration misc net
+QAPI_COMMON_MODULES += dump error introspect job machine migration misc net
 QAPI_COMMON_MODULES += qdev qom rdma rocker run-state sockets tpm
 QAPI_COMMON_MODULES += trace transaction ui
 QAPI_TARGET_MODULES = machine-target misc-target

qapi/common.json

@@ -4,30 +4,6 @@
 # = Common data types
 ##
 
-##
-# @QapiErrorClass:
-#
-# QEMU error classes
-#
-# @GenericError: this is used for errors that don't require a specific error
-#                class. This should be the default case for most errors
-#
-# @CommandNotFound: the requested command has not been found
-#
-# @DeviceNotActive: a device has failed to be become active
-#
-# @DeviceNotFound: the requested device has not been found
-#
-# @KVMMissingCap: the requested operation can't be fulfilled because a
-#                 required KVM capability is missing
-#
-# Since: 1.2
-##
-{ 'enum': 'QapiErrorClass',
-  # Keep this in sync with ErrorClass in error.h
-  'data': [ 'GenericError', 'CommandNotFound',
-            'DeviceNotActive', 'DeviceNotFound', 'KVMMissingCap' ] }
-
 ##
 # @IoOperationType:
 #

qapi/error.json

@@ -0,0 +1,29 @@
+# -*- Mode: Python -*-
+
+##
+# = QMP errors
+##
+
+##
+# @QapiErrorClass:
+#
+# QEMU error classes
+#
+# @GenericError: this is used for errors that don't require a specific error
+#                class. This should be the default case for most errors
+#
+# @CommandNotFound: the requested command has not been found
+#
+# @DeviceNotActive: a device has failed to be become active
+#
+# @DeviceNotFound: the requested device has not been found
+#
+# @KVMMissingCap: the requested operation can't be fulfilled because a
+#                 required KVM capability is missing
+#
+# Since: 1.2
+##
+{ 'enum': 'QapiErrorClass',
+  # Keep this in sync with ErrorClass in error.h
+  'data': [ 'GenericError', 'CommandNotFound',
+            'DeviceNotActive', 'DeviceNotFound', 'KVMMissingCap' ] }

qapi/qapi-schema.json

@@ -80,6 +80,7 @@
 # stable order, it's best to include each sub-schema just once, or
 # include it first right here.
 
+{ 'include': 'error.json' }
 { 'include': 'common.json' }
 { 'include': 'sockets.json' }
 { 'include': 'run-state.json' }