[PATCH v2 3/9] qapi: start building an 'if' predicate tree

[marcandre . lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

The following patches are going to express conditions in a target
language agnostic way. For that, let's start building a predicate tree
of configuration options.

This intermediary steps still uses C-preprocessor expressions as
predicates: "if: [STR, ..]" is translated to a "IfCond -> IfAll ->
IfOption[STR]" tree, which will generate "#if STR && .." C code. After
the necessary condition tree nodes are introduced, the 'if' C
expressions will be converted.

(the tree will be less expressive than the full C macros expressions,
and will be based only on identifiers. It will only support these
operations over the configuration identifiers: 'all', 'any' and 'not')

For now, the documentation will continue to use a C condition
expression (with defined(FOO), &&, || etc). Eventually, we may want to
generate a more human friendly syntax later.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 docs/sphinx/qapidoc.py                 |  6 +--
 scripts/qapi/common.py                 | 42 ++++++++++++++++++-
 scripts/qapi/schema.py                 | 47 +++++++++++----------
 tests/qapi-schema/doc-good.out         | 12 +++---
 tests/qapi-schema/qapi-schema-test.out | 58 +++++++++++++-------------
 5 files changed, 104 insertions(+), 61 deletions(-)

diff --git a/docs/sphinx/qapidoc.py b/docs/sphinx/qapidoc.py
index db9520f37f..31b47e4745 100644
--- a/docs/sphinx/qapidoc.py
+++ b/docs/sphinx/qapidoc.py
@@ -112,12 +112,10 @@ class QAPISchemaGenRSTVisitor(QAPISchemaVisitor):
     def _nodes_for_ifcond(self, ifcond, with_if=True):
         """Return list of Text, literal nodes for the ifcond
 
-        Return a list which gives text like ' (If: cond1, cond2, cond3)', where
-        the conditions are in literal-text and the commas are not.
+        Return a list which gives text like ' (If: C-condition)'.
         If with_if is False, we don't return the "(If: " and ")".
         """
-        condlist = intersperse([nodes.literal('', c) for c in ifcond.ifcond],
-                               nodes.Text(', '))
+        condlist = [nodes.literal('', ifcond.gen_if())]
         if not with_if:
             return condlist
 
diff --git a/scripts/qapi/common.py b/scripts/qapi/common.py
index 6ee72956b5..01c4c0c878 100644
--- a/scripts/qapi/common.py
+++ b/scripts/qapi/common.py
@@ -12,7 +12,7 @@
 # See the COPYING file in the top-level directory.
 
 import re
-from typing import Optional
+from typing import Optional, Sequence
 
 
 #: Magic string that gets removed along with all space to its right.
@@ -192,3 +192,43 @@ def guardend(name: str) -> str:
 #endif /* %(name)s */
 ''',
                  name=c_fname(name).upper())
+
+
+class IfPredicate:
+    def cgen(self) -> str:
+        raise NotImplementedError()
+
+
+class IfOption(IfPredicate):
+    def __init__(self, option: str):
+        self.option = option
+
+    def cgen(self) -> str:
+        return self.option
+
+    def __repr__(self) -> str:
+        return repr(self.option)
+
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, IfOption):
+            return False
+        return self.option == other.option
+
+
+class IfAll(IfPredicate):
+    def __init__(self, pred_list: Sequence[IfPredicate]):
+        self.pred_list = pred_list
+
+    def cgen(self) -> str:
+        return " && ".join([p.cgen() for p in self.pred_list])
+
+    def __bool__(self) -> bool:
+        return bool(self.pred_list)
+
+    def __repr__(self) -> str:
+        return f"IfAll({self.pred_list})"
+
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, IfAll):
+            return False
+        return self.pred_list == other.pred_list
diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index 92961aedcf..4a4dbf2da7 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -70,7 +70,13 @@ from typing import (
     overload,
 )
 
-from .common import POINTER_SUFFIX, c_name, mcgen
+from .common import (
+    POINTER_SUFFIX,
+    IfAll,
+    IfOption,
+    c_name,
+    mcgen,
+)
 from .error import QAPISemError, QAPISourceError
 from .expr import check_exprs
 from .parser import ParsedExpression, QAPIDoc, QAPISchemaParser
@@ -87,34 +93,33 @@ class Visitable:
 
 class QAPISchemaIf:
     def __init__(self, ifcond: Optional[Sequence[str]] = None):
-        self.ifcond = ifcond or []
-
-    def gen_if(self) -> str:
-        ret = ''
-        for ifc in self.ifcond:
-            ret += mcgen('''
-#if %(cond)s
-''', cond=ifc)
-        return ret
-
-    def gen_endif(self) -> str:
-        ret = ''
-        for ifc in reversed(self.ifcond):
-            ret += mcgen('''
-#endif /* %(cond)s */
-''', cond=ifc)
-        return ret
+        pred_list = [IfOption(opt) for opt in ifcond or []]
+        self.pred = IfAll(pred_list)
 
     def __bool__(self) -> bool:
-        return bool(self.ifcond)
+        return bool(self.pred)
 
     def __repr__(self) -> str:
-        return repr(self.ifcond)
+        return repr(self.pred)
 
     def __eq__(self, other: object) -> bool:
         if not isinstance(other, QAPISchemaIf):
             return NotImplemented
-        return self.ifcond == other.ifcond
+        return self.pred == other.pred
+
+    def gen_if(self) -> str:
+        if self.pred:
+            return mcgen('''
+#if %(cond)s
+''', cond=self.pred.cgen())
+        return ""
+
+    def gen_endif(self) -> str:
+        if self.pred:
+            return mcgen('''
+#endif // %(cond)s
+''', cond=self.pred.cgen())
+        return ""
 
 
 class QAPISchemaEntity(Visitable):
diff --git a/tests/qapi-schema/doc-good.out b/tests/qapi-schema/doc-good.out
index 419284dae2..0d27323c47 100644
--- a/tests/qapi-schema/doc-good.out
+++ b/tests/qapi-schema/doc-good.out
@@ -12,15 +12,15 @@ enum QType
 module doc-good.json
 enum Enum
     member one
-        if ['defined(IFONE)']
+        if IfAll(['defined(IFONE)'])
     member two
-    if ['defined(IFCOND)']
+    if IfAll(['defined(IFCOND)'])
     feature enum-feat
 object Base
     member base1: Enum optional=False
 object Variant1
     member var1: str optional=False
-        if ['defined(IFSTR)']
+        if IfAll(['defined(IFSTR)'])
         feature member-feat
     feature variant1-feat
 object Variant2
@@ -29,7 +29,7 @@ object Object
     tag base1
     case one: Variant1
     case two: Variant2
-        if ['IFTWO']
+        if IfAll(['IFTWO'])
     feature union-feat1
 object q_obj_Variant1-wrapper
     member data: Variant1 optional=False
@@ -38,13 +38,13 @@ object q_obj_Variant2-wrapper
 enum SugaredUnionKind
     member one
     member two
-        if ['IFTWO']
+        if IfAll(['IFTWO'])
 object SugaredUnion
     member type: SugaredUnionKind optional=False
     tag type
     case one: q_obj_Variant1-wrapper
     case two: q_obj_Variant2-wrapper
-        if ['IFTWO']
+        if IfAll(['IFTWO'])
     feature union-feat2
 alternate Alternate
     tag type
diff --git a/tests/qapi-schema/qapi-schema-test.out 
b/tests/qapi-schema/qapi-schema-test.out
index 8868ca0dca..8ba658cd38 100644
--- a/tests/qapi-schema/qapi-schema-test.out
+++ b/tests/qapi-schema/qapi-schema-test.out
@@ -298,65 +298,65 @@ command __org.qemu_x-command 
q_obj___org.qemu_x-command-arg -> __org.qemu_x-Unio
 object TestIfStruct
     member foo: int optional=False
     member bar: int optional=False
-        if ['defined(TEST_IF_STRUCT_BAR)']
-    if ['defined(TEST_IF_STRUCT)']
+        if IfAll(['defined(TEST_IF_STRUCT_BAR)'])
+    if IfAll(['defined(TEST_IF_STRUCT)'])
 enum TestIfEnum
     member foo
     member bar
-        if ['defined(TEST_IF_ENUM_BAR)']
-    if ['defined(TEST_IF_ENUM)']
+        if IfAll(['defined(TEST_IF_ENUM_BAR)'])
+    if IfAll(['defined(TEST_IF_ENUM)'])
 object q_obj_TestStruct-wrapper
     member data: TestStruct optional=False
 enum TestIfUnionKind
     member foo
     member union_bar
-        if ['defined(TEST_IF_UNION_BAR)']
-    if ['defined(TEST_IF_UNION) && defined(TEST_IF_STRUCT)']
+        if IfAll(['defined(TEST_IF_UNION_BAR)'])
+    if IfAll(['defined(TEST_IF_UNION) && defined(TEST_IF_STRUCT)'])
 object TestIfUnion
     member type: TestIfUnionKind optional=False
     tag type
     case foo: q_obj_TestStruct-wrapper
     case union_bar: q_obj_str-wrapper
-        if ['defined(TEST_IF_UNION_BAR)']
-    if ['defined(TEST_IF_UNION) && defined(TEST_IF_STRUCT)']
+        if IfAll(['defined(TEST_IF_UNION_BAR)'])
+    if IfAll(['defined(TEST_IF_UNION) && defined(TEST_IF_STRUCT)'])
 object q_obj_TestIfUnionCmd-arg
     member union_cmd_arg: TestIfUnion optional=False
-    if ['defined(TEST_IF_UNION)']
+    if IfAll(['defined(TEST_IF_UNION)'])
 command TestIfUnionCmd q_obj_TestIfUnionCmd-arg -> None
     gen=True success_response=True boxed=False oob=False preconfig=False
-    if ['defined(TEST_IF_UNION)']
+    if IfAll(['defined(TEST_IF_UNION)'])
 alternate TestIfAlternate
     tag type
     case foo: int
     case bar: TestStruct
-        if ['defined(TEST_IF_ALT_BAR)']
-    if ['defined(TEST_IF_ALT) && defined(TEST_IF_STRUCT)']
+        if IfAll(['defined(TEST_IF_ALT_BAR)'])
+    if IfAll(['defined(TEST_IF_ALT) && defined(TEST_IF_STRUCT)'])
 object q_obj_TestIfAlternateCmd-arg
     member alt_cmd_arg: TestIfAlternate optional=False
-    if ['defined(TEST_IF_ALT)']
+    if IfAll(['defined(TEST_IF_ALT)'])
 command TestIfAlternateCmd q_obj_TestIfAlternateCmd-arg -> None
     gen=True success_response=True boxed=False oob=False preconfig=False
-    if ['defined(TEST_IF_ALT)']
+    if IfAll(['defined(TEST_IF_ALT)'])
 object q_obj_TestIfCmd-arg
     member foo: TestIfStruct optional=False
     member bar: TestIfEnum optional=False
-        if ['defined(TEST_IF_CMD_BAR)']
-    if ['defined(TEST_IF_CMD)', 'defined(TEST_IF_STRUCT)']
+        if IfAll(['defined(TEST_IF_CMD_BAR)'])
+    if IfAll(['defined(TEST_IF_CMD)', 'defined(TEST_IF_STRUCT)'])
 command TestIfCmd q_obj_TestIfCmd-arg -> UserDefThree
     gen=True success_response=True boxed=False oob=False preconfig=False
-    if ['defined(TEST_IF_CMD)', 'defined(TEST_IF_STRUCT)']
+    if IfAll(['defined(TEST_IF_CMD)', 'defined(TEST_IF_STRUCT)'])
 command TestCmdReturnDefThree None -> UserDefThree
     gen=True success_response=True boxed=False oob=False preconfig=False
 array TestIfEnumList TestIfEnum
-    if ['defined(TEST_IF_ENUM)']
+    if IfAll(['defined(TEST_IF_ENUM)'])
 object q_obj_TestIfEvent-arg
     member foo: TestIfStruct optional=False
     member bar: TestIfEnumList optional=False
-        if ['defined(TEST_IF_EVT_BAR)']
-    if ['defined(TEST_IF_EVT) && defined(TEST_IF_STRUCT)']
+        if IfAll(['defined(TEST_IF_EVT_BAR)'])
+    if IfAll(['defined(TEST_IF_EVT) && defined(TEST_IF_STRUCT)'])
 event TestIfEvent q_obj_TestIfEvent-arg
     boxed=False
-    if ['defined(TEST_IF_EVT) && defined(TEST_IF_STRUCT)']
+    if IfAll(['defined(TEST_IF_EVT) && defined(TEST_IF_STRUCT)'])
 object FeatureStruct0
     member foo: int optional=False
 object FeatureStruct1
@@ -379,17 +379,17 @@ object FeatureStruct4
 object CondFeatureStruct1
     member foo: int optional=False
     feature feature1
-        if ['defined(TEST_IF_FEATURE_1)']
+        if IfAll(['defined(TEST_IF_FEATURE_1)'])
 object CondFeatureStruct2
     member foo: int optional=False
     feature feature1
-        if ['defined(TEST_IF_FEATURE_1)']
+        if IfAll(['defined(TEST_IF_FEATURE_1)'])
     feature feature2
-        if ['defined(TEST_IF_FEATURE_2)']
+        if IfAll(['defined(TEST_IF_FEATURE_2)'])
 object CondFeatureStruct3
     member foo: int optional=False
     feature feature1
-        if ['defined(TEST_IF_COND_1)', 'defined(TEST_IF_COND_2)']
+        if IfAll(['defined(TEST_IF_COND_1)', 'defined(TEST_IF_COND_2)'])
 enum FeatureEnum1
     member eins
     member zwei
@@ -429,17 +429,17 @@ command test-command-features3 None -> None
 command test-command-cond-features1 None -> None
     gen=True success_response=True boxed=False oob=False preconfig=False
     feature feature1
-        if ['defined(TEST_IF_FEATURE_1)']
+        if IfAll(['defined(TEST_IF_FEATURE_1)'])
 command test-command-cond-features2 None -> None
     gen=True success_response=True boxed=False oob=False preconfig=False
     feature feature1
-        if ['defined(TEST_IF_FEATURE_1)']
+        if IfAll(['defined(TEST_IF_FEATURE_1)'])
     feature feature2
-        if ['defined(TEST_IF_FEATURE_2)']
+        if IfAll(['defined(TEST_IF_FEATURE_2)'])
 command test-command-cond-features3 None -> None
     gen=True success_response=True boxed=False oob=False preconfig=False
     feature feature1
-        if ['defined(TEST_IF_COND_1)', 'defined(TEST_IF_COND_2)']
+        if IfAll(['defined(TEST_IF_COND_1)', 'defined(TEST_IF_COND_2)'])
 event TEST-EVENT-FEATURES1 None
     boxed=False
     feature deprecated
-- 
2.29.0