qapi/error: Repurpose QAPIError as an abstract base exception class

Rename QAPIError to QAPISourceError, and then create a new QAPIError
class that serves as the basis for all of our other custom exceptions,
without specifying any class properties.

This leaves QAPIError as a package-wide error class that's suitable for
any current or future errors.

(Right now, we don't have any errors that DON'T also want to specify a
Source location, but this MAY change. In these cases, a common abstract
ancestor would be desired.)

Add docstrings to explain the intended function of each error class.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20210421192233.3542904-2-jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/scripts/qapi/error.py b/scripts/qapi/error.py
index ae60d9e2fe..126dda7c9b 100644
--- a/scripts/qapi/error.py
+++ b/scripts/qapi/error.py
@@ -13,6 +13,11 @@
 
 
 class QAPIError(Exception):
+    """Base class for all exceptions from the QAPI package."""
+
+
+class QAPISourceError(QAPIError):
+    """Error class for all exceptions identifying a source location."""
     def __init__(self, info, col, msg):
         Exception.__init__(self)
         self.info = info
@@ -27,7 +32,8 @@ class QAPIError(Exception):
         return loc + ': ' + self.msg
 
 
-class QAPIParseError(QAPIError):
+class QAPIParseError(QAPISourceError):
+    """Error class for all QAPI schema parsing errors."""
     def __init__(self, parser, msg):
         col = 1
         for ch in parser.src[parser.line_pos:parser.pos]:
@@ -38,6 +44,7 @@ class QAPIParseError(QAPIError):
         super().__init__(parser.info, col, msg)
 
 
-class QAPISemError(QAPIError):
+class QAPISemError(QAPISourceError):
+    """Error class for semantic QAPI errors."""
     def __init__(self, info, msg):
         super().__init__(info, None, msg)