qapi: Improve include file name reporting in error messages

Error messages print absolute file names of included files even if the
user gave a relative one on the command line:

    $ PYTHONPATH=scripts python -B tests/qapi-schema/test-qapi.py tests/qapi-schema/include-cycle.json
    In file included from tests/qapi-schema/include-cycle.json:1:
    In file included from /work/armbru/qemu/tests/qapi-schema/include-cycle-b.json:1:
    /work/armbru/qemu/tests/qapi-schema/include-cycle-c.json:1: Inclusion loop for include-cycle.json

Improve this to

    In file included from tests/qapi-schema/include-cycle.json:1:
    In file included from tests/qapi-schema/include-cycle-b.json:1:
    tests/qapi-schema/include-cycle-c.json:1: Inclusion loop for include-cycle.json

The error message when an include file can't be opened prints the
include directive's file name, which is relative to the including
file.  Change this to print the file name relative to the working
directory.  Visible in tests/qapi-schema/include-no-file.err.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180211093607.27351-12-armbru@redhat.com>
Reviewed-by: NMichael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: NEric Blake <eblake@redhat.com>

scripts/qapi/common.py

@@ -259,9 +259,8 @@ class QAPIDoc(object):
 class QAPISchemaParser(object):
 
     def __init__(self, fp, previously_included=[], incl_info=None):
-        abs_fname = os.path.abspath(fp.name)
         self.fname = fp.name
-        previously_included.append(abs_fname)
+        previously_included.append(os.path.abspath(fp.name))
         self.incl_info = incl_info
         self.src = fp.read()
         if self.src == '' or self.src[-1] != '\n':
@@ -292,7 +291,7 @@ class QAPISchemaParser(object):
                 if not isinstance(include, str):
                     raise QAPISemError(info,
                                        "Value of 'include' must be a string")
-                self._include(include, info, os.path.dirname(abs_fname),
+                self._include(include, info, os.path.dirname(self.fname),
                               previously_included)
             elif "pragma" in expr:
                 self.reject_expr_doc(cur_doc)
@@ -325,7 +324,8 @@ class QAPISchemaParser(object):
                 % doc.symbol)
 
     def _include(self, include, info, base_dir, previously_included):
-        incl_abs_fname = os.path.join(base_dir, include)
+        incl_fname = os.path.join(base_dir, include)
+        incl_abs_fname = os.path.abspath(incl_fname)
         # catch inclusion cycle
         inf = info
         while inf:
@@ -337,9 +337,9 @@ class QAPISchemaParser(object):
         if incl_abs_fname in previously_included:
             return
         try:
-            fobj = open(incl_abs_fname, 'r')
+            fobj = open(incl_fname, 'r')
         except IOError as e:
-            raise QAPISemError(info, '%s: %s' % (e.strerror, include))
+            raise QAPISemError(info, '%s: %s' % (e.strerror, incl_fname))
         exprs_include = QAPISchemaParser(fobj, previously_included, info)
         self.exprs.extend(exprs_include.exprs)
         self.docs.extend(exprs_include.docs)

tests/qapi-schema/include-no-file.err

-tests/qapi-schema/include-no-file.json:1: No such file or directory: include-no-file-sub.json
+tests/qapi-schema/include-no-file.json:1: No such file or directory: tests/qapi-schema/include-no-file-sub.json