[Qemu-devel] [PATCH v10 05/25] qapi: Reserve 'q_*' and 'has_*' member names

[Eric Blake <eblake@redhat.com>]

c_name() produces names starting with 'q_' when protecting
a QMP member name that would fail to directly compile, but
in doing so can cause clashes with any QMP name already
beginning with 'q-' or 'q_'.  Likewise, we create a C name
'has_' for any optional member, that can clash with any QMP
name beginning with 'has-' or 'has_'.

Technically, rather than blindly reserving the namespace,
we could try to complain about user names only when an actual
collision occurs, or even teach c_name() how to munge names
to avoid collisions.  But it is not trivial, especially when
collisions can occur across multiple types (such as via
inheritance or flat unions).  Besides, no existing .json
files are trying to use these names.  So it's easier to just
outright forbid the potential for collision.  We can always
relax things in the future if a real need arises for QMP to
express member names that have been forbidden here.

'has_' only has to be reserved for struct/union member names,
while 'q_' is reserved everywhere (matching the fact that
we only have optional members, but use c_name() everywhere).

Update and add tests to cover the new error messages.

Signed-off-by: Eric Blake <eblake@redhat.com>

---
v10: retitle, improve comments, defer 'u' changes for later, use
c_name(name).startswith('has_') rather than open coding
v9: new patch
---
 docs/qapi-code-gen.txt                  | 11 +++++++----
 scripts/qapi.py                         |  8 +++++++-
 tests/qapi-schema/args-has-clash.err    |  1 +
 tests/qapi-schema/args-has-clash.exit   |  2 +-
 tests/qapi-schema/args-has-clash.json   |  8 ++++----
 tests/qapi-schema/args-has-clash.out    |  6 ------
 tests/qapi-schema/reserved-command.err  |  1 +
 tests/qapi-schema/reserved-command.exit |  2 +-
 tests/qapi-schema/reserved-command.json |  7 +++----
 tests/qapi-schema/reserved-command.out  |  5 -----
 tests/qapi-schema/reserved-member.err   |  1 +
 tests/qapi-schema/reserved-member.exit  |  2 +-
 tests/qapi-schema/reserved-member.json  |  7 +++----
 tests/qapi-schema/reserved-member.out   |  4 ----
 14 files changed, 30 insertions(+), 35 deletions(-)

diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
index c4264a8..4d8c2fc 100644
--- a/docs/qapi-code-gen.txt
+++ b/docs/qapi-code-gen.txt
@@ -112,7 +112,9 @@ and field names within a type, should be all lower case with words
 separated by a hyphen.  However, some existing older commands and
 complex types use underscore; when extending such expressions,
 consistency is preferred over blindly avoiding underscore.  Event
-names should be ALL_CAPS with words separated by underscore.
+names should be ALL_CAPS with words separated by underscore.  Field
+names cannot start with 'has-' or 'has_', as this is reserved for
+tracking optional fields.

 Any name (command, event, type, field, or enum value) beginning with
 "x-" is marked experimental, and may be withdrawn or changed
@@ -123,9 +125,10 @@ vendor), even if the rest of the name uses dash (example:
 __com.redhat_drive-mirror).  Other than downstream extensions (with
 leading underscore and the use of dots), all names should begin with a
 letter, and contain only ASCII letters, digits, dash, and underscore.
-It is okay to reuse names that match C keywords; the generator will
-rename a field named "default" in the QAPI to "q_default" in the
-generated C code.
+Names beginning with 'q_' are reserved for the generator: QMP names
+that resemble C keywords or other problematic strings will be munged
+in C to use this prefix.  For example, a field named "default" in
+qapi becomes "q_default" in the generated C code.

 In the rest of this document, usage lines are given for each
 expression type, with literal strings written in lower case and
diff --git a/scripts/qapi.py b/scripts/qapi.py
index d53b5c4..04bcbf7 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -376,7 +376,9 @@ def check_name(expr_info, source, name, allow_optional=False,
     # code always prefixes it with the enum name
     if enum_member:
         membername = '_' + membername
-    if not valid_name.match(membername):
+    # Reserve the entire 'q_' namespace for c_name()
+    if not valid_name.match(membername) or \
+       membername.replace('-', '_').startswith('q_'):
         raise QAPIExprError(expr_info,
                             "%s uses invalid name '%s'" % (source, name))

@@ -488,6 +490,10 @@ def check_type(expr_info, source, value, allow_array=False,
     for (key, arg) in value.items():
         check_name(expr_info, "Member of %s" % source, key,
                    allow_optional=allow_optional)
+        if c_name(key).startswith('has_'):
+            raise QAPIExprError(expr_info,
+                                "Member of %s uses reserved name '%s'"
+                                % (source, key))
         # Todo: allow dictionaries to represent default values of
         # an optional argument.
         check_type(expr_info, "Member '%s' of %s" % (key, source), arg,
diff --git a/tests/qapi-schema/args-has-clash.err b/tests/qapi-schema/args-has-clash.err
index e69de29..595fe93 100644
--- a/tests/qapi-schema/args-has-clash.err
+++ b/tests/qapi-schema/args-has-clash.err
@@ -0,0 +1 @@
+tests/qapi-schema/args-has-clash.json:6: Member of 'data' for command 'oops' uses reserved name 'has-a'
diff --git a/tests/qapi-schema/args-has-clash.exit b/tests/qapi-schema/args-has-clash.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/args-has-clash.exit
+++ b/tests/qapi-schema/args-has-clash.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/args-has-clash.json b/tests/qapi-schema/args-has-clash.json
index a2197de..38453e7 100644
--- a/tests/qapi-schema/args-has-clash.json
+++ b/tests/qapi-schema/args-has-clash.json
@@ -1,6 +1,6 @@
 # C member name collision
-# FIXME - This parses, but fails to compile, because the C struct is given
-# two 'has_a' members, one from the flag for optional 'a', and the other
-# from member 'has-a'.  Either reject this at parse time, or munge the C
-# names to avoid the collision.
+# This would attempt to create two 'has_a' members of the C struct, one
+# from the flag for optional 'a', and the other from member 'has-a'; so
+# instead we reject any member with a name that would collide with 'has_'.
+# TODO we could munge the optional flag name to avoid the collision.
 { 'command': 'oops', 'data': { '*a': 'str', 'has-a': 'str' } }
diff --git a/tests/qapi-schema/args-has-clash.out b/tests/qapi-schema/args-has-clash.out
index 5a18b6b..e69de29 100644
--- a/tests/qapi-schema/args-has-clash.out
+++ b/tests/qapi-schema/args-has-clash.out
@@ -1,6 +0,0 @@
-object :empty
-object :obj-oops-arg
-    member a: str optional=True
-    member has-a: str optional=False
-command oops :obj-oops-arg -> None
-   gen=True success_response=True
diff --git a/tests/qapi-schema/reserved-command.err b/tests/qapi-schema/reserved-command.err
index e69de29..a70856b 100644
--- a/tests/qapi-schema/reserved-command.err
+++ b/tests/qapi-schema/reserved-command.err
@@ -0,0 +1 @@
+tests/qapi-schema/reserved-command.json:6: 'command' uses invalid name 'q-unix'
diff --git a/tests/qapi-schema/reserved-command.exit b/tests/qapi-schema/reserved-command.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/reserved-command.exit
+++ b/tests/qapi-schema/reserved-command.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/reserved-command.json b/tests/qapi-schema/reserved-command.json
index be9944c..d662a96 100644
--- a/tests/qapi-schema/reserved-command.json
+++ b/tests/qapi-schema/reserved-command.json
@@ -1,7 +1,6 @@
 # C entity name collision
-# FIXME - This parses, but fails to compile, because it attempts to declare
-# two 'qmp_q_unix' functions (one for 'q-unix', the other because c_name()
-# munges 'unix' to 'q_unix' to avoid reserved word collisions). We should
-# reject attempts to explicitly use 'q_' names, to reserve it for qapi.
+# This would attempt to declare two 'qmp_q_unix' functions (one for 'q-unix',
+# the other because c_name() munges 'unix' to 'q_unix' to avoid reserved word
+# collisions). Therefore, we reserve 'q_' names for qapi.
 { 'command': 'unix' }
 { 'command': 'q-unix' }
diff --git a/tests/qapi-schema/reserved-command.out b/tests/qapi-schema/reserved-command.out
index b31b38f..e69de29 100644
--- a/tests/qapi-schema/reserved-command.out
+++ b/tests/qapi-schema/reserved-command.out
@@ -1,5 +0,0 @@
-object :empty
-command q-unix None -> None
-   gen=True success_response=True
-command unix None -> None
-   gen=True success_response=True
diff --git a/tests/qapi-schema/reserved-member.err b/tests/qapi-schema/reserved-member.err
index e69de29..8752c5b 100644
--- a/tests/qapi-schema/reserved-member.err
+++ b/tests/qapi-schema/reserved-member.err
@@ -0,0 +1 @@
+tests/qapi-schema/reserved-member.json:5: Member of 'data' for struct 'Foo' uses invalid name 'q-unix'
diff --git a/tests/qapi-schema/reserved-member.exit b/tests/qapi-schema/reserved-member.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/reserved-member.exit
+++ b/tests/qapi-schema/reserved-member.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/reserved-member.json b/tests/qapi-schema/reserved-member.json
index 1602ed3..a8dac22 100644
--- a/tests/qapi-schema/reserved-member.json
+++ b/tests/qapi-schema/reserved-member.json
@@ -1,6 +1,5 @@
 # C member name collision
-# FIXME - This parses, but fails to compile, because it attempts to declare
-# two 'q_unix' members (one for 'q-unix', the other because c_name()
-# munges 'unix' to 'q_unix' to avoid reserved word collisions). We should
-# reject attempts to explicitly use 'q_' names, to reserve it for qapi.
+# This would attempt to declare two 'q_unix' members (one for 'q-unix',
+# the other because c_name() munges 'unix' to 'q_unix' to avoid reserved word
+# collisions). Therefore, we reserve 'q_' names for qapi.
 { 'struct': 'Foo', 'data': { 'unix':'int', 'q-unix':'bool' } }
diff --git a/tests/qapi-schema/reserved-member.out b/tests/qapi-schema/reserved-member.out
index 0d8685a..e69de29 100644
--- a/tests/qapi-schema/reserved-member.out
+++ b/tests/qapi-schema/reserved-member.out
@@ -1,4 +0,0 @@
-object :empty
-object Foo
-    member unix: int optional=False
-    member q-unix: bool optional=False
-- 
2.4.3