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Tue, 27 Apr 2021 09:00:38 +0200 (CEST) From: Markus Armbruster To: John Snow Subject: Re: [PATCH 10/22] qapi/parser: Fix typing of token membership tests References: <20210422030720.3685766-1-jsnow@redhat.com> <20210422030720.3685766-11-jsnow@redhat.com> <87v98a7q23.fsf@dusky.pond.sub.org> <78cf87ce-ce02-d9d6-0922-84a328b6b9da@redhat.com> Date: Tue, 27 Apr 2021 09:00:38 +0200 In-Reply-To: <78cf87ce-ce02-d9d6-0922-84a328b6b9da@redhat.com> (John Snow's message of "Mon, 26 Apr 2021 13:51:34 -0400") Message-ID: <87k0oo6wkp.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.219, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michael Roth , Cleber Rosa , qemu-devel@nongnu.org, Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" John Snow writes: > On 4/25/21 3:59 AM, Markus Armbruster wrote: >> John Snow writes: >> >>> When the token can be None, we can't use 'x in "abc"' style membership >>> tests to group types of tokens together, because 'None in "abc"' is a >>> TypeError. >>> >>> Easy enough to fix, if not a little ugly. >>> >>> Signed-off-by: John Snow >>> --- >>> scripts/qapi/parser.py | 5 +++-- >>> 1 file changed, 3 insertions(+), 2 deletions(-) >>> >>> diff --git a/scripts/qapi/parser.py b/scripts/qapi/parser.py >>> index 7f3c009f64b..16fd36f8391 100644 >>> --- a/scripts/qapi/parser.py >>> +++ b/scripts/qapi/parser.py >>> @@ -272,7 +272,7 @@ def get_values(self): >>> if self.tok == ']': >>> self.accept() >>> return expr >>> - if self.tok not in "{['tf": >>> + if self.tok is None or self.tok not in "{['tf": >>> raise QAPIParseError( >>> self, "expected '{', '[', ']', string, or boolean") >>> while True: >>> @@ -294,7 +294,8 @@ def get_expr(self, nested): >>> elif self.tok == '[': >>> self.accept() >>> expr = self.get_values() >>> - elif self.tok in "'tf": >>> + elif self.tok and self.tok in "'tf": >>> + assert isinstance(self.val, (str, bool)) >>> expr = self.val >>> self.accept() >>> else: >> >> How can self.tok be None? >> >> I suspect this is an artifact of PATCH 04. Before, self.tok is >> initialized to the first token, then set to subsequent tokens (all str) >> in turn. After, it's initialized to None, then set to tokens in turn. >> > > Actually, it's set to None to represent EOF. See here: > > elif self.tok == '\n': > if self.cursor == len(self.src): > self.tok = None > return Alright, then this is actually a bug fix: $ echo -n "{'key': " | python3 scripts/qapi-gen.py /dev/stdin Traceback (most recent call last): File "scripts/qapi-gen.py", line 19, in sys.exit(main.main()) File "/work/armbru/qemu/scripts/qapi/main.py", line 93, in main generate(args.schema, File "/work/armbru/qemu/scripts/qapi/main.py", line 50, in generate schema = QAPISchema(schema_file) File "/work/armbru/qemu/scripts/qapi/schema.py", line 852, in __init__ parser = QAPISchemaParser(fname) File "/work/armbru/qemu/scripts/qapi/parser.py", line 59, in __init__ self._parse() File "/work/armbru/qemu/scripts/qapi/parser.py", line 81, in _parse expr = self.get_expr(False) File "/work/armbru/qemu/scripts/qapi/parser.py", line 293, in get_expr expr = self.get_members() File "/work/armbru/qemu/scripts/qapi/parser.py", line 260, in get_members expr[key] = self.get_expr(True) File "/work/armbru/qemu/scripts/qapi/parser.py", line 297, in get_expr elif self.tok in "'tf": TypeError: 'in ' requires string as left operand, not NoneType Likewise, the other hunk: $ echo -n "{'key': [" | python3 scripts/qapi-gen.py /dev/stdin Traceback (most recent call last): File "scripts/qapi-gen.py", line 19, in sys.exit(main.main()) File "/work/armbru/qemu/scripts/qapi/main.py", line 89, in main generate(args.schema, File "/work/armbru/qemu/scripts/qapi/main.py", line 51, in generate schema = QAPISchema(schema_file) File "/work/armbru/qemu/scripts/qapi/schema.py", line 860, in __init__ parser = QAPISchemaParser(fname) File "/work/armbru/qemu/scripts/qapi/parser.py", line 71, in __init__ expr = self.get_expr(False) File "/work/armbru/qemu/scripts/qapi/parser.py", line 270, in get_expr expr = self.get_members() File "/work/armbru/qemu/scripts/qapi/parser.py", line 238, in get_members expr[key] = self.get_expr(True) File "/work/armbru/qemu/scripts/qapi/parser.py", line 273, in get_expr expr = self.get_values() File "/work/armbru/qemu/scripts/qapi/parser.py", line 253, in get_values if self.tok not in "{['tf": TypeError: 'in ' requires string as left operand, not NoneType Please add test cases. I recommend adding them in a separate patch, so this one's diff shows clearly what's being fixed. There's a similar one in accept(), but it's safe: self.tok = self.src[self.cursor] ... elif self.tok in '{}:,[]': return Regarding "if not a little ugly": instead of self.tok is None or self.tok not in "{['tf" we could use self.tok not in tuple("{['tf") > A more pythonic idiom would be to create a lexer class that behaves as > an iterator, yielding Token class objects, and eventually, raising > StopIteration. > > (Not suggesting I do that now. I have thought about it though, yes.) Yes, let's resist the temptation to improve things into too many directions at once. Aside: using exceptions for perfectly unexceptional things like loop termination is in questionable taste, but we gotta go with the Python flow.