qapi: Prefix frontend errors with an "in definition" line

We take pains to include the offending expression in error messages,
e.g.

    tests/qapi-schema/alternate-any.json:2: alternate 'Alt' member 'one' cannot use type 'any'

But not always:

    tests/qapi-schema/enum-if-invalid.json:2: 'if' condition must be a string or a list of strings

Instead of improving them one by one, report the offending expression
whenever it is known, like this:

    tests/qapi-schema/enum-if-invalid.json: In enum 'TestIfEnum':
    tests/qapi-schema/enum-if-invalid.json:2: 'if' condition must be a string or a list of strings

Error messages that mention the offending expression become a bit
redundant, e.g.

    tests/qapi-schema/alternate-any.json: In alternate 'Alt':
    tests/qapi-schema/alternate-any.json:2: alternate 'Alt' member 'one' cannot use type 'any'

I'll take care of that later in this series.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190927134639.4284-5-armbru@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/tests/qapi-schema/alternate-nested.err b/tests/qapi-schema/alternate-nested.err
index 4d1187e60e..4ab5328025 100644
--- a/tests/qapi-schema/alternate-nested.err
+++ b/tests/qapi-schema/alternate-nested.err
@@ -1 +1,2 @@
+tests/qapi-schema/alternate-nested.json: In alternate 'Alt2':
 tests/qapi-schema/alternate-nested.json:4: Member 'nested' of alternate 'Alt2' cannot use alternate type 'Alt1'