[PATCH v2 09/16] scripts/qapi: add QAPISchemaIfCond.rsgen()

From: Marc-André Lureau <[email protected]>

Generate Rust #[cfg(...)] guards from QAPI 'if' conditions; it
turns out that they are very similar, with both of them using
not/any/all, so just walk the tree.

The next commit will put it to use.

Signed-off-by: Marc-André Lureau <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Paolo Bonzini <[email protected]>
---
 scripts/qapi/common.py | 19 +++++++++++++++++++
 scripts/qapi/schema.py |  4 ++++
 2 files changed, 23 insertions(+)

diff --git a/scripts/qapi/common.py b/scripts/qapi/common.py
index d7c8aa3365c..14d5dd259c4 100644
--- a/scripts/qapi/common.py
+++ b/scripts/qapi/common.py
@@ -199,6 +199,25 @@ def guardend(name: str) -> str:
                  name=c_fname(name).upper())
 
 
+def rsgen_ifcond(ifcond: Optional[Union[str, Dict[str, Any]]]) -> str:
+
+    def cfg(ifcond: Union[str, Dict[str, Any]]) -> str:
+        if isinstance(ifcond, str):
+            return ifcond
+        assert isinstance(ifcond, dict) and len(ifcond) == 1
+        if 'not' in ifcond:
+            oper = 'not'
+            arg = cfg(ifcond['not'])
+        else:
+            oper, operands = next(iter(ifcond.items()))
+            arg = ', '.join([cfg(c) for c in operands])
+        return f'{oper}({arg})'
+
+    if not ifcond:
+        return ''
+    return '#[cfg(%s)]' % cfg(ifcond)
+
+
 def gen_ifcond(ifcond: Optional[Union[str, Dict[str, Any]]],
                cond_fmt: str, not_fmt: str,
                all_operator: str, any_operator: str) -> str:
diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index 8d88b40de2e..848a7401251 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -37,6 +37,7 @@
     docgen_ifcond,
     gen_endif,
     gen_if,
+    rsgen_ifcond,
 )
 from .error import QAPIError, QAPISemError, QAPISourceError
 from .expr import check_exprs
@@ -63,6 +64,9 @@ def gen_endif(self) -> str:
     def docgen(self) -> str:
         return docgen_ifcond(self.ifcond)
 
+    def rsgen(self) -> str:
+        return rsgen_ifcond(self.ifcond)
+
     def is_present(self) -> bool:
         return bool(self.ifcond)
 
-- 
2.52.0