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Re: [PATCH v2 05/11] qapi/introspect.py: add preliminary type hint annot
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From: |
John Snow |
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Subject: |
Re: [PATCH v2 05/11] qapi/introspect.py: add preliminary type hint annotations |
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Date: |
Mon, 7 Dec 2020 18:48:23 -0500 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 |
On 11/13/20 11:48 AM, Markus Armbruster wrote:
John Snow <jsnow@redhat.com> writes:
The typing of _make_tree and friends is a bit involved, but it can be
done with some stubbed out types and a bit of elbow grease. The
forthcoming patches attempt to make some simplifications, but having the
type hints in advance may aid in review of subsequent patches.
Some notes on the abstract types used at this point, and what they
represent:
- TreeValue represents any object in the type tree. _make_tree is an
optional call -- not every node in the final type tree will have been
passed to _make_tree, so this type encompasses not only what is passed
to _make_tree (dicts, strings) or returned from it (dicts, strings, a
2-tuple), but any recursive value for any of the dicts passed to
_make_tree -- which includes lists, strings, integers, null constants,
and so on.
- _DObject is a type alias I use to mean "A JSON-style object,
represented as a Python dict." There is no "JSON" type in Python, they
are converted natively to recursively nested dicts and lists, with
leaf values of str, int, float, None, True/False and so on. This type
structure is not possible to accurately portray in mypy yet, so a
placeholder is used.
In this case, _DObject is being used to refer to SchemaInfo-like
structures as defined in qapi/introspect.json, OR any sub-object
values they may reference. We don't have strong typing available for
those, so a generic alternative is used.
- Extra refers explicitly to the dict containing "extra" information
about a node in the tree. mypy does not offer per-key typing for dicts
in Python 3.6, so this is the best we can do here.
- Annotated refers to (one of) the return types of _make_tree:
It represents a 2-tuple of (TreeValue, Extra).
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
---
scripts/qapi/introspect.py | 157 ++++++++++++++++++++++++++++---------
scripts/qapi/mypy.ini | 5 --
scripts/qapi/schema.py | 2 +-
3 files changed, 121 insertions(+), 43 deletions(-)
diff --git a/scripts/qapi/introspect.py b/scripts/qapi/introspect.py
index 63f721ebfb6..803288a64e7 100644
--- a/scripts/qapi/introspect.py
+++ b/scripts/qapi/introspect.py
@@ -10,7 +10,16 @@
See the COPYING file in the top-level directory.
"""
-from typing import Optional, Sequence, cast
+from typing import (
+ Any,
+ Dict,
+ List,
+ Optional,
+ Sequence,
+ Tuple,
+ Union,
+ cast,
+)
from .common import (
c_name,
@@ -20,13 +29,56 @@
)
from .gen import QAPISchemaMonolithicCVisitor
from .schema import (
+ QAPISchema,
QAPISchemaArrayType,
QAPISchemaBuiltinType,
+ QAPISchemaEntity,
+ QAPISchemaEnumMember,
+ QAPISchemaFeature,
+ QAPISchemaObjectType,
+ QAPISchemaObjectTypeMember,
QAPISchemaType,
+ QAPISchemaVariant,
+ QAPISchemaVariants,
)
+from .source import QAPISourceInfo
-def _make_tree(obj, ifcond, features, extra=None):
+# This module constructs a tree-like data structure that is used to
"Tree-like" suggests it's not a tree, it just looks like one if you
squint. Drop "-like"?
Sure. I think I am grammatically predisposed to assume "binary tree" or
at least some kind of monomorphic tree when I see "tree", hence the
hedging and weasel-words.
No problem just to drop it.
+# generate the introspection information for QEMU. It behaves similarly
+# to a JSON value.
+#
+# A complexity over JSON is that our values may or may not be annotated.
It's the obvious abstract syntax tree for JSON, hacked up^W^Wextended to
support certain annotations.
Yes.
Let me add a bit of context and history.
The module's job is generating qapi-introspect.[ch] for a QAPISchema.
The purpose of qapi-introspect.[ch] is providing the information
query-qmp-schema needs, i.e. (a suitable C representation of) a JSON
value conforming to [SchemaInfo]. Details of this C representation are
not interesting right now.
We first go from QAPISchema to a suitable Python representation of
[SchemaInfo], then from there to the C source code, neatly separating
concerns.
Stupidest solution Python representation that could possibly work: the
obvious abstract syntax tree for JSON (that's also how Python's json
module works).
Parts corresponding to QAPISchema parts guarded by 'if' conditionals
need to be guarded by #if conditionals.
We want to prefix parts corresponding to certain QAPISchema parts with a
comment.
These two requirements came later, and were hacked into the existing
stupidest solution: any tree node can be a tuple (json, extra), where
json is the "stupidest" node, and extra is a dict of annotations. In
other words, to annotate an unannotated node N with dict D, replace N by
(N, D).
Possible annotations:
'comment': str
'if': Sequence[str]
They say there are just three answers a Marine may give to an officer's
questions: "Yes, sir!", "No, sir!", "No excuse, sir!". Let me put that
to use here:
Is this an elegant design? No, sir!
Is the code easy to read? No excuse, sir!
Was it cheap to make? Yes, sir!
Yes, I believe I am on the same page so far. It was difficult to read
and difficult to annotate, but once I got to the bottom, it's easy to
see why it happened this way in retrospect. It's the simplest thing that
could work.
And it does work!
So far, this comment isn't really a correction on what I wrote, but if
you believe my comment that explains the types could be clearer, feel
free to suggest.
+#
+# Un-annotated values may be:
+# Scalar: str, bool, None.
+# Non-scalar: List, Dict
+# _Value = Union[str, bool, None, Dict[str, Value], List[Value]]
+#
+# With optional annotations, the type of all values is:
+# TreeValue = Union[_Value, Annotated[_Value]]
+#
+# Sadly, mypy does not support recursive types, so we must approximate this.
+_stub = Any
+_scalar = Union[str, bool, None]
+_nonscalar = Union[Dict[str, _stub], List[_stub]]
+_value = Union[_scalar, _nonscalar]
+TreeValue = Union[_value, 'Annotated']
Are there naming conventions for this kind of variables? I'm asking
because you capitalize some, but not all, and I can't see a pattern.
Types generally get CamelCase names; though for interior aliases I used
underscore + lowercase. In this case, I was trying to illustrate that
these intermediate types were only interesting or useful in service of
the Capitalized Thing, TreeValue.
Ignorant question: only 'Annotated' has quotes; why?
It hasn't been defined yet, so it's a forward reference. Cleber
suggested I hoist its definition up to avoid this. I forget if I had
some strong reason for doing it this way, admittedly.
A lot of this code gets changed shortly in the following patches, so
honestly I was likely just not really putting in a lot of effort to make
code that gets deleted soon pretty.
(Why did the patches go in that order then? During early review, Eduardo
wanted to see the type hints go in first to help review for the cleanup
be easier ...!)
There is "_Value", "Value" and "_value". Suggest to add "value"
somewhere, for completeness ;-P
Yeah, my mistake. See my response to Cleber here...
I find the names _value and TreeValue a bit unfortunate: the difference
between the two isn't Tree. I'll come back to this below.
Feel free to suggest something better; I am at a point with this
particular module where I'd be happy to have someone more opinionated
than me telling me what they want.
+
+# This is just an alias for an object in the structure described above:
+_DObject = Dict[str, object]
I'm confused. Which structure, and why do we want to alias it?
Yep, I don't have a good name for this either. I mean this to be a
generic type that describes the natural python representation for a JSON
object.
i.e. Dict[str, THING].
All of the various bits and pieces here that are generating SchemaInfo
subtype representations (like _gen_member, _gen_variant, etc.) are using
this as a generic "Well, it's some kind of dict/object."
(Aside: this is an interesting part of code, because it is not type safe
with respect to the QAPI definitions that define SchemaInfo's descendant
types. There's no more explicit type for me to use here to describe
those objects.)
+
+# Represents the annotations themselves:
+Annotations = Dict[str, object]
Losely typed. I have no idea whether that's bad :)
Kind of: unlike Any, using 'object' means that if we treat the
dictionary values in a manner that we could not treat *all* values, mypy
will raise an error.
So it is a very broad type, but it's "safe".
+
+# Represents an annotated node (of some kind).
+Annotated = Tuple[_value, Annotations]
So, _value seems to represent a JSON value, Annotated an annotated JSON
value, and TreeValue their union, i.e. a possibly annotated JSON value.
Naming is hard... BareJsonValue, AnnotatedJsonValue, JsonValue?
I was afraid of using "JsonValue" to avoid implicating it as a literal
JSON value -- since it isn't, exactly. It's the Python native
approximation of a subset of JSON values.
+
+
+def _make_tree(obj: Union[_DObject, str], ifcond: List[str],
I'd expect obj: _value, i.e. "unannotated value".
Sure, and I believe that would work -- this type is "tighter".
_make_tree only ever sees Dict[str, object] and str, actually.
Later in the series, _make_tree goes away and this weird sub-type also
goes away in favor of the more generic type.
+ features: List[QAPISchemaFeature],
+ extra: Optional[Annotations] = None
+ ) -> TreeValue:
if extra is None:
extra = {}
if ifcond:
@@ -39,9 +91,11 @@ def _make_tree(obj, ifcond, features, extra=None):
return obj
-def _tree_to_qlit(obj, level=0, suppress_first_indent=False):
+def _tree_to_qlit(obj: TreeValue,
+ level: int = 0,
+ suppress_first_indent: bool = False) -> str:
- def indent(level):
+ def indent(level: int) -> str:
return level * 4 * ' '
if isinstance(obj, tuple):
@@ -91,21 +145,20 @@ def indent(level):
return ret
-def to_c_string(string):
+def to_c_string(string: str) -> str:
return '"' + string.replace('\\', r'\\').replace('"', r'\"') + '"'
class QAPISchemaGenIntrospectVisitor(QAPISchemaMonolithicCVisitor):
-
Intentional?
I'm sure I thought it looked nice at the time. It's not important.
- def __init__(self, prefix, unmask):
+ def __init__(self, prefix: str, unmask: bool):
super().__init__(
prefix, 'qapi-introspect',
' * QAPI/QMP schema introspection', __doc__)
self._unmask = unmask
- self._schema = None
- self._trees = []
- self._used_types = []
- self._name_map = {}
+ self._schema: Optional[QAPISchema] = None
+ self._trees: List[TreeValue] = []
+ self._used_types: List[QAPISchemaType] = []
+ self._name_map: Dict[str, str] = {}
self._genc.add(mcgen('''
#include "qemu/osdep.h"
#include "%(prefix)sqapi-introspect.h"
@@ -113,10 +166,10 @@ def __init__(self, prefix, unmask):
''',
prefix=prefix))
- def visit_begin(self, schema):
+ def visit_begin(self, schema: QAPISchema) -> None:
self._schema = schema
- def visit_end(self):
+ def visit_end(self) -> None:
# visit the types that are actually used
for typ in self._used_types:
typ.visit(self)
@@ -138,18 +191,18 @@ def visit_end(self):
self._used_types = []
self._name_map = {}
- def visit_needed(self, entity):
+ def visit_needed(self, entity: QAPISchemaEntity) -> bool:
# Ignore types on first pass; visit_end() will pick up used types
return not isinstance(entity, QAPISchemaType)
- def _name(self, name):
+ def _name(self, name: str) -> str:
if self._unmask:
return name
if name not in self._name_map:
self._name_map[name] = '%d' % len(self._name_map)
return self._name_map[name]
- def _use_type(self, typ):
+ def _use_type(self, typ: QAPISchemaType) -> str:
# Map the various integer types to plain int
if typ.json_type() == 'int':
typ = self._schema.lookup_type('int')
@@ -168,8 +221,10 @@ def _use_type(self, typ):
return '[' + self._use_type(typ.element_type) + ']'
return self._name(typ.name)
- def _gen_tree(self, name, mtype, obj, ifcond, features):
- extra = None
+ def _gen_tree(self, name: str, mtype: str, obj: _DObject,
+ ifcond: List[str],
+ features: Optional[List[QAPISchemaFeature]]) -> None:
_gen_tree() builds a complete tree (i.e. one SchemaInfo), and adds it to
._trees.
The SchemaInfo's common parts are name, meta-type and features.
_gen_tree() takes them as arguments @name, @mtype, @features.
It takes SchemaInfo's variant parts as a dict @obj.
It completes @obj into an unannotated tree node by the common parts into
@obj.
It also takes a QAPI conditional argument @ifcond.
Now let me review the type annotations:
* name: str matches SchemaInfo, good.
* mtype: str approximates SchemaInfo's enum SchemaMetaType (it's not
Python Enum because those were off limits when this code was written).
It's also a little cumbersome, perhaps, to duplicate information from
the QAPI schema directly into the QAPI generator.
Didn't feel like getting clever enough to "fix" this.
* obj: _DObject ... I'd expect "unannotated JSON value".
It's NOT any value though -- like you said: "_gen_tree() builds a
complete tree (i.e. one SchemaInfo)" -- we only accept objects here,
which is correct.
* ifcond: List[str] should work, but gen_if(), gen_endif() use
Sequence[str]. Suggest to pick one (please explain why), and stick to
it.
More instances of ifcond: List[str] elsewhere; I'm not flagging them.
Yes, I should probably be using Sequence, if I can. generally:
- Input types should use the most generic type they can cope with
(Iterable, Sequence, Collection) based on what properties they actually
need in the incoming type.
(By the end of this series, Iterable[str] should actually be sufficient,
but I'll have to see where it makes sense to slacken the input types in
this series. It's been through the washer quite a few times I'm afraid.)
- Output types should be as explicit as possible.
I was not always perfectly good about generalizing the input types; List
is correct, but not necessarily maximally correct.
* features: Optional[List[QAPISchemaFeature]] is correct. "No features"
has two representations: None and []. I guess we could eliminate
None, trading a tiny bit of efficiency for simpler typing. Not a
demand.
+ extra: Optional[Annotations] = None
"No annotations" is represented as None here, not {}. I guess we could
use {} for simpler typing. Not a demand.
This goes away later, kinda. It becomes:
comment: Optional[str] = None
and that comment is eventually passed to an Annotated node constructor
that takes the comment specifically.
if mtype not in ('command', 'event', 'builtin', 'array'):
if not self._unmask:
# Output a comment to make it easy to map masked names
@@ -180,44 +235,64 @@ def _gen_tree(self, name, mtype, obj, ifcond, features):
obj['meta-type'] = mtype
self._trees.append(_make_tree(obj, ifcond, features, extra))
- def _gen_member(self, member):
- obj = {'name': member.name, 'type': self._use_type(member.type)}
+ def _gen_member(self,
+ member: QAPISchemaObjectTypeMember) -> TreeValue:
+ obj: _DObject = {
I'd expect "unannotated value". More of the same below.
See my remark to your expectation for what _gen_tree should accept. It
deals with "objects" and "objects" have the property that more keys can
be assigned to them, and this is a fundamental feature of _gen_tree.
+ 'name': member.name,
+ 'type': self._use_type(member.type)
+ }
if member.optional:
obj['default'] = None
return _make_tree(obj, member.ifcond, member.features)
- def _gen_variants(self, tag_name, variants):
+ def _gen_variants(self, tag_name: str,
+ variants: List[QAPISchemaVariant]) -> _DObject:
return {'tag': tag_name,
'variants': [self._gen_variant(v) for v in variants]}
- def _gen_variant(self, variant):
- obj = {'case': variant.name, 'type': self._use_type(variant.type)}
+ def _gen_variant(self, variant: QAPISchemaVariant) -> TreeValue:
+ obj: _DObject = {
+ 'case': variant.name,
+ 'type': self._use_type(variant.type)
+ }
return _make_tree(obj, variant.ifcond, None)
- def visit_builtin_type(self, name, info, json_type):
+ def visit_builtin_type(self, name: str, info: Optional[QAPISourceInfo],
A built-in's type info is always None. Perhaps we should drop the
parameter.
QAPISchemaBuiltinType -> QAPISchemaType -> QAPISchemaEntity
This class ultimately takes an info parameter in the constructor which
is Optional, which means that the type for the info field is
Optional[QAPISourceInfo].
If you want to remove the parameter here, that works.
+ json_type: str) -> None:
self._gen_tree(name, 'builtin', {'json-type': json_type}, [], None)
- def visit_enum_type(self, name, info, ifcond, features, members, prefix):
+ def visit_enum_type(self, name: str, info: QAPISourceInfo,
+ ifcond: List[str], features: List[QAPISchemaFeature],
+ members: List[QAPISchemaEnumMember],
+ prefix: Optional[str]) -> None:
self._gen_tree(name, 'enum',
{'values': [_make_tree(m.name, m.ifcond, None)
for m in members]},
ifcond, features)
- def visit_array_type(self, name, info, ifcond, element_type):
+ def visit_array_type(self, name: str, info: Optional[QAPISourceInfo],
Here, @info is indeed optional: it's None when @element_type is a
built-in type.
+ ifcond: List[str],
+ element_type: QAPISchemaType) -> None:
element = self._use_type(element_type)
self._gen_tree('[' + element + ']', 'array', {'element-type':
element},
ifcond, None)
- def visit_object_type_flat(self, name, info, ifcond, features,
- members, variants):
- obj = {'members': [self._gen_member(m) for m in members]}
+ def visit_object_type_flat(self, name: str, info: Optional[QAPISourceInfo],
And here it is optional due to the internal object type 'q_empty'.
+ ifcond: List[str],
+ features: List[QAPISchemaFeature],
+ members: Sequence[QAPISchemaObjectTypeMember],
+ variants: Optional[QAPISchemaVariants]) -> None:
We represent "no variants" as None, not as []. I guess we could
eliminate use [], trading a tiny bit of efficiency for simpler typing.
Not a demand.
For a later series:
I recommend turning QAPISchemaVariants into an extension of
Sequence[QAPISchemaVariant], and then always creating an empty
collection for the purpose of simplifying the type signature.
I'd recommend the following magicks:
__bool__ -- for writing "if variants: ..."
__iter__ -- for writing "for variant in variants: ..."
Then we can just always say "variants: QAPISchemaVariants" and go about
our lives.
(Maybe that won't work, QAPISchemaVariants has a lot of other parameters
it takes that maybe don't apply to empty collections. Something to come
back to, I think.)
+ obj: _DObject = {'members': [self._gen_member(m) for m in members]}
if variants:
obj.update(self._gen_variants(variants.tag_member.name,
variants.variants))
self._gen_tree(name, 'object', obj, ifcond, features)
- def visit_alternate_type(self, name, info, ifcond, features, variants):
+ def visit_alternate_type(self, name: str, info: QAPISourceInfo,
+ ifcond: List[str],
+ features: List[QAPISchemaFeature],
+ variants: QAPISchemaVariants) -> None:
self._gen_tree(name, 'alternate',
{'members': [
_make_tree({'type': self._use_type(m.type)},
@@ -225,24 +300,32 @@ def visit_alternate_type(self, name, info, ifcond,
features, variants):
for m in variants.variants]},
ifcond, features)
- def visit_command(self, name, info, ifcond, features,
- arg_type, ret_type, gen, success_response, boxed,
- allow_oob, allow_preconfig, coroutine):
+ def visit_command(self, name: str, info: QAPISourceInfo, ifcond: List[str],
+ features: List[QAPISchemaFeature],
+ arg_type: QAPISchemaObjectType,
+ ret_type: Optional[QAPISchemaType], gen: bool,
Are you sure arg_type can't be None?
I am not.
Strict optional checking is still disabled at this point in the series,
there are problems like this that it would uncover if I turned it on,
but many other errors are spurious. I could change approach and begin
enabling it right away to make these discrepancies go away -- at the
expense of maybe more "noise" with various assertions and other fluff.
Turning on strict optional at the beginning of part 2 shows 96 errors.
Adding a quick dumb type kludge for genc/genh, there's 18 errors prior
to series 2. I can make a "part 1.5" and try to whittle that down to
zero if you're willing to review it. Another quick edit to commands.py,
I'm down to 15 errors all in gen.py.
It might be a lot of frustrating fluff, but it will make Optional[T] vs
T auditing a bit easier (if not more cumbersome on the way.)
In order to turn it on, though, I do have to go all the way to the end
of the six parts, and then backport the fixes to the earlier parts. You
won't necessarily notice a difference until schema.py itself is fully typed.
--js
+ success_response: bool, boxed: bool, allow_oob: bool,
+ allow_preconfig: bool, coroutine: bool) -> None:
arg_type = arg_type or self._schema.the_empty_object_type
ret_type = ret_type or self._schema.the_empty_object_type
- obj = {'arg-type': self._use_type(arg_type),
- 'ret-type': self._use_type(ret_type)}
+ obj: _DObject = {
+ 'arg-type': self._use_type(arg_type),
+ 'ret-type': self._use_type(ret_type)
+ }
if allow_oob:
obj['allow-oob'] = allow_oob
self._gen_tree(name, 'command', obj, ifcond, features)
- def visit_event(self, name, info, ifcond, features, arg_type, boxed):
+ def visit_event(self, name: str, info: QAPISourceInfo,
+ ifcond: List[str], features: List[QAPISchemaFeature],
+ arg_type: QAPISchemaObjectType, boxed: bool) -> None:
arg_type = arg_type or self._schema.the_empty_object_type
self._gen_tree(name, 'event', {'arg-type': self._use_type(arg_type)},
ifcond, features)
-def gen_introspect(schema, output_dir, prefix, opt_unmask):
+def gen_introspect(schema: QAPISchema, output_dir: str, prefix: str,
+ opt_unmask: bool) -> None:
vis = QAPISchemaGenIntrospectVisitor(prefix, opt_unmask)
schema.visit(vis)
vis.write(output_dir)
diff --git a/scripts/qapi/mypy.ini b/scripts/qapi/mypy.ini
index 74fc6c82153..c0f2a58306d 100644
--- a/scripts/qapi/mypy.ini
+++ b/scripts/qapi/mypy.ini
@@ -14,11 +14,6 @@ disallow_untyped_defs = False
disallow_incomplete_defs = False
check_untyped_defs = False
-[mypy-qapi.introspect]
-disallow_untyped_defs = False
-disallow_incomplete_defs = False
-check_untyped_defs = False
-
[mypy-qapi.parser]
disallow_untyped_defs = False
disallow_incomplete_defs = False
diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index 720449feee4..e91b77fadc3 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -28,7 +28,7 @@
class QAPISchemaEntity:
meta: Optional[str] = None
- def __init__(self, name, info, doc, ifcond=None, features=None):
+ def __init__(self, name: str, info, doc, ifcond=None, features=None):
assert name is None or isinstance(name, str)
for f in features or []:
assert isinstance(f, QAPISchemaFeature)