[RFC PATCH v2 1/8] qapi: golang: Generate qapi's enum types in Go

[Victor Toso]

This patch handles QAPI enum types and generates its equivalent in Go.

Basically, Enums are being handled as strings in Golang.

1. For each QAPI enum, we will define a string type in Go to be the
   assigned type of this specific enum.

2. Naming: CamelCase will be used in any identifier that we want to
   export [0], which is everything.

[0] https://go.dev/ref/spec#Exported_identifiers

Example:

qapi:
  | { 'enum': 'DisplayProtocol',
  |   'data': [ 'vnc', 'spice' ] }

go:
  | type DisplayProtocol string
  |
  | const (
  |     DisplayProtocolVnc   DisplayProtocol = "vnc"
  |     DisplayProtocolSpice DisplayProtocol = "spice"
  | )

Signed-off-by: Victor Toso <victortoso@redhat.com>
---
 scripts/qapi/golang.py | 134 +++++++++++++++++++++++++++++++++++++++++
 scripts/qapi/main.py   |   2 +
 2 files changed, 136 insertions(+)
 create mode 100644 scripts/qapi/golang.py

diff --git a/scripts/qapi/golang.py b/scripts/qapi/golang.py
new file mode 100644
index 0000000000..f2776520a1
--- /dev/null
+++ b/scripts/qapi/golang.py
@@ -0,0 +1,134 @@
+"""
+Golang QAPI generator
+"""
+# Copyright (c) 2022 Red Hat Inc.
+#
+# Authors:
+#  Victor Toso <victortoso@redhat.com>
+#
+# This work is licensed under the terms of the GNU GPL, version 2.
+# See the COPYING file in the top-level directory.
+
+# Just for type hint on self
+from __future__ import annotations
+
+import os
+from typing import List, Optional
+
+from .schema import (
+    QAPISchema,
+    QAPISchemaType,
+    QAPISchemaVisitor,
+    QAPISchemaEnumMember,
+    QAPISchemaFeature,
+    QAPISchemaIfCond,
+    QAPISchemaObjectType,
+    QAPISchemaObjectTypeMember,
+    QAPISchemaVariants,
+)
+from .source import QAPISourceInfo
+
+
+class QAPISchemaGenGolangVisitor(QAPISchemaVisitor):
+
+    def __init__(self, prefix: str):
+        super().__init__()
+        self.target = {name: "" for name in ["enum"]}
+        self.schema = None
+        self.golang_package_name = "qapi"
+
+    def visit_begin(self, schema):
+        self.schema = schema
+
+        # Every Go file needs to reference its package name
+        for target in self.target:
+            self.target[target] = f"package {self.golang_package_name}\n"
+
+    def visit_end(self):
+        self.schema = None
+
+    def visit_object_type(self: QAPISchemaGenGolangVisitor,
+                          name: str,
+                          info: Optional[QAPISourceInfo],
+                          ifcond: QAPISchemaIfCond,
+                          features: List[QAPISchemaFeature],
+                          base: Optional[QAPISchemaObjectType],
+                          members: List[QAPISchemaObjectTypeMember],
+                          variants: Optional[QAPISchemaVariants]
+                          ) -> None:
+        pass
+
+    def visit_alternate_type(self: QAPISchemaGenGolangVisitor,
+                             name: str,
+                             info: Optional[QAPISourceInfo],
+                             ifcond: QAPISchemaIfCond,
+                             features: List[QAPISchemaFeature],
+                             variants: QAPISchemaVariants
+                             ) -> None:
+        pass
+
+    def visit_enum_type(self: QAPISchemaGenGolangVisitor,
+                        name: str,
+                        info: Optional[QAPISourceInfo],
+                        ifcond: QAPISchemaIfCond,
+                        features: List[QAPISchemaFeature],
+                        members: List[QAPISchemaEnumMember],
+                        prefix: Optional[str]
+                        ) -> None:
+
+        value = qapi_to_field_name_enum(members[0].name)
+        fields = ""
+        for member in members:
+            value = qapi_to_field_name_enum(member.name)
+            fields += f'''\t{name}{value} {name} = "{member.name}"\n'''
+
+        self.target["enum"] += f'''
+type {name} string
+const (
+{fields[:-1]}
+)
+'''
+
+    def visit_array_type(self, name, info, ifcond, element_type):
+        pass
+
+    def visit_command(self,
+                      name: str,
+                      info: Optional[QAPISourceInfo],
+                      ifcond: QAPISchemaIfCond,
+                      features: List[QAPISchemaFeature],
+                      arg_type: Optional[QAPISchemaObjectType],
+                      ret_type: Optional[QAPISchemaType],
+                      gen: bool,
+                      success_response: bool,
+                      boxed: bool,
+                      allow_oob: bool,
+                      allow_preconfig: bool,
+                      coroutine: bool) -> None:
+        pass
+
+    def visit_event(self, name, info, ifcond, features, arg_type, boxed):
+        pass
+
+    def write(self, output_dir: str) -> None:
+        for module_name, content in self.target.items():
+            go_module = module_name + "s.go"
+            go_dir = "go"
+            pathname = os.path.join(output_dir, go_dir, go_module)
+            odir = os.path.dirname(pathname)
+            os.makedirs(odir, exist_ok=True)
+
+            with open(pathname, "w") as outfile:
+                outfile.write(content)
+
+
+def gen_golang(schema: QAPISchema,
+               output_dir: str,
+               prefix: str) -> None:
+    vis = QAPISchemaGenGolangVisitor(prefix)
+    schema.visit(vis)
+    vis.write(output_dir)
+
+
+def qapi_to_field_name_enum(name: str) -> str:
+    return name.title().replace("-", "")
diff --git a/scripts/qapi/main.py b/scripts/qapi/main.py
index fc216a53d3..661fb1e091 100644
--- a/scripts/qapi/main.py
+++ b/scripts/qapi/main.py
@@ -15,6 +15,7 @@
 from .common import must_match
 from .error import QAPIError
 from .events import gen_events
+from .golang import gen_golang
 from .introspect import gen_introspect
 from .schema import QAPISchema
 from .types import gen_types
@@ -54,6 +55,7 @@ def generate(schema_file: str,
     gen_events(schema, output_dir, prefix)
     gen_introspect(schema, output_dir, prefix, unmask)
 
+    gen_golang(schema, output_dir, prefix)
 
 def main() -> int:
     """
-- 
2.36.1