feat: microgen - adds code generation logic (#2294)

* chore: removes old proof of concept

* removes old __init__.py

* Adds two utility files to handle basic tasks

* Adds a configuration file for the microgenerator

* Removes unused comment

* chore: adds noxfile.py for the microgenerator

* feat: microgen - adds two init file templates

* feat: adds _helpers.py.js  template

* Updates with two usage examples

* feat: adds two partial templates for creating method signatures

* feat: Add microgenerator __init__.py

Migrates the empty __init__.py file to the microgenerator package.

* feat: Add AST analysis utilities

Introduces the CodeAnalyzer class and helper functions for parsing Python code using the ast module. This provides the foundation for understanding service client structures.

* feat: Add source file analysis capabilities
    Implements functions to analyze Python source files, including:
    - Filtering classes and methods based on configuration.
    - Building a schema of request classes and their arguments.
    - Processing service client files to extract relevant information.

* feat: adds code generation logic

* removes extraneous content

* feat: microgen - adds code generation logic

* Adds Path class and changes path to package

* refactors a complicated loop into two separate helpers

Author: chalmerlowe

scripts/microgenerator/generate.py

@@ -26,9 +26,9 @@
 import os
 import glob
 import logging
-import re
 from collections import defaultdict
-from typing import List, Dict, Any, Iterator
+from pathlib import Path
+from typing import List, Dict, Any
 
 from . import name_utils
 from . import utils
@@ -492,3 +492,129 @@ def analyze_source_files(
 
     return parsed_data, all_imports, all_types, request_arg_schema
 
+
+# =============================================================================
+# Section 3: Code Generation
+# =============================================================================
+
+
+def _generate_import_statement(
+    context: List[Dict[str, Any]], key: str, package: str
+) -> str:
+    """Generates a formatted import statement from a list of context dictionaries.
+
+    Args:
+        context: A list of dictionaries containing the data.
+        key: The key to extract from each dictionary in the context.
+        package: The base import package (e.g., "google.cloud.bigquery_v2.services").
+
+    Returns:
+        A formatted, multi-line import statement string.
+    """
+
+    names = sorted(list(set([item[key] for item in context])))
+    names_str = ",\n    ".join(names)
+    return f"from {package} import (\n    {names_str}\n)"
+
+
+def _get_request_class_name(method_name: str, config: Dict[str, Any]) -> str:
+    """Gets the inferred request class name, applying overrides from config."""
+    inferred_request_name = name_utils.method_to_request_class_name(method_name)
+    method_overrides = config.get("filter", {}).get("methods", {}).get("overrides", {})
+    if method_name in method_overrides:
+        return method_overrides[method_name].get(
+            "request_class_name", inferred_request_name
+        )
+    return inferred_request_name
+
+
+def _find_fq_request_name(
+    request_name: str, request_arg_schema: Dict[str, List[str]]
+) -> str:
+    """Finds the fully qualified request name in the schema."""
+    for key in request_arg_schema.keys():
+        if key.endswith(f".{request_name}"):
+            return key
+    return ""
+
+
+def generate_code(config: Dict[str, Any], analysis_results: tuple) -> None:
+    """
+    Generates source code files using Jinja2 templates.
+    """
+
+    data, all_imports, all_types, request_arg_schema = analysis_results
+    project_root = config["project_root"]
+    config_dir = config["config_dir"]
+
+    templates_config = config.get("templates", [])
+    for item in templates_config:
+        template_path = str(Path(config_dir) / item["template"])
+        output_path = str(Path(project_root) / item["output"])
+
+        template = utils.load_template(template_path)
+        methods_context = []
+        for class_name, methods in data.items():
+            for method_name, method_info in methods.items():
+                context = {
+                    "name": method_name,
+                    "class_name": class_name,
+                    "return_type": method_info["return_type"],
+                }
+
+                request_name = _get_request_class_name(method_name, config)
+                fq_request_name = _find_fq_request_name(
+                    request_name, request_arg_schema
+                )
+
+                if fq_request_name:
+                    context["request_class_full_name"] = fq_request_name
+                    context["request_id_args"] = request_arg_schema[fq_request_name]
+
+                methods_context.append(context)
+
+        # Prepare imports for the template
+        services_context = []
+        client_class_names = sorted(
+            list(set([m["class_name"] for m in methods_context]))
+        )
+
+        for class_name in client_class_names:
+            service_name_cluster = name_utils.generate_service_names(class_name)
+            services_context.append(service_name_cluster)
+
+        # Also need to update methods_context to include the service_name and module_name
+        # so the template knows which client to use for each method.
+        class_to_service_map = {s["service_client_class"]: s for s in services_context}
+        for method in methods_context:
+            service_info = class_to_service_map.get(method["class_name"])
+            if service_info:
+                method["service_name"] = service_info["service_name"]
+                method["service_module_name"] = service_info["service_module_name"]
+
+        # Prepare new imports
+        service_imports = [
+            _generate_import_statement(
+                services_context,
+                "service_module_name",
+                "google.cloud.bigquery_v2.services",
+            )
+        ]
+
+        # Prepare type imports
+        type_imports = [
+            _generate_import_statement(
+                services_context, "service_name", "google.cloud.bigquery_v2.types"
+            )
+        ]
+
+        final_code = template.render(
+            service_name=config.get("service_name"),
+            methods=methods_context,
+            services=services_context,
+            service_imports=service_imports,
+            type_imports=type_imports,
+            request_arg_schema=request_arg_schema,
+        )
+
+        utils.write_code_to_file(output_path, final_code)