fix(http-client-python): preserve customized pyproject.toml fields

.chronus/changes/preserve-pyproject-fields-2026-06-15-feature.md

@@ -0,0 +1,16 @@
+---
+changeKind: feature
+packages:
+  - "@typespec/http-client-python"
+---
+
+Add a `keep-pyproject-fields` emitter option that selects which `[project]` fields to preserve in an existing `pyproject.toml` instead of overwriting them on regeneration. Supported fields: `authors`, `description`, `classifiers`, `urls`.
+
+```yaml
+# tspconfig.yaml
+options:
+  "@typespec/http-client-python":
+    keep-pyproject-fields:
+      authors: true
+      description: true
+```

packages/http-client-python/emitter/src/emitter.ts

@@ -210,6 +210,14 @@ async function onEmitMain(context: EmitContext<PythonEmitterOptions>) {
     commandArgs["packaging-files-config"] = keyValuePairs.join("|");
     resolvedOptions["packaging-files-config"] = undefined;
   }
+  if (resolvedOptions["keep-pyproject-fields"]) {
+    // Flatten the object of enabled fields into a comma-separated list for the generator.
+    const enabledFields = Object.entries(resolvedOptions["keep-pyproject-fields"])
+      .filter(([, value]) => value === true)
+      .map(([key]) => key);
+    commandArgs["keep-pyproject-fields"] = enabledFields.join(",");
+    resolvedOptions["keep-pyproject-fields"] = undefined;
+  }
 
   for (const [key, value] of Object.entries(resolvedOptions)) {
     if (key === "license") continue; // skip license since it is passed in codeModel

packages/http-client-python/emitter/src/lib.ts

@@ -24,6 +24,12 @@ export interface PythonEmitterOptions {
   "head-as-boolean"?: boolean;
   "use-pyodide"?: boolean;
   "keep-setup-py"?: boolean;
+  "keep-pyproject-fields"?: {
+    authors?: boolean;
+    description?: boolean;
+    classifiers?: boolean;
+    urls?: boolean;
+  };
   "clear-output-folder"?: boolean;
   "emit-yaml-only"?: boolean;
 }
@@ -105,6 +111,36 @@ export const PythonEmitterOptionsSchema: JSONSchemaType<PythonEmitterOptions> =
       description:
         "Whether to keep the existing `setup.py` when `generate-packaging-files` is `true`. If set to `false` and by default, `pyproject.toml` will be generated instead. To generate `setup.py`, use `basic-setup-py`.",
     },
+    "keep-pyproject-fields": {
+      type: "object",
+      nullable: true,
+      description:
+        "Which manually customized `[project]` fields to preserve in an existing `pyproject.toml` instead of overwriting them on regeneration. Set a field to `true` to keep it. By default no fields are preserved.",
+      properties: {
+        authors: {
+          type: "boolean",
+          nullable: true,
+          description: "Preserve the `authors` field (e.g. a custom author name and email).",
+        },
+        description: {
+          type: "boolean",
+          nullable: true,
+          description: "Preserve the `description` field.",
+        },
+        classifiers: {
+          type: "boolean",
+          nullable: true,
+          description: "Preserve the `classifiers` field.",
+        },
+        urls: {
+          type: "boolean",
+          nullable: true,
+          description: "Preserve the `[project.urls]` table.",
+        },
+      },
+      required: [],
+      additionalProperties: false,
+    },
     "clear-output-folder": {
       type: "boolean",
       nullable: true,

packages/http-client-python/generator/pygen/__init__.py

@@ -29,6 +29,7 @@ class OptionsDict(MutableMapping):
         "from-typespec": False,
         "generate-sample": False,
         "keep-setup-py": False,
+        "keep-pyproject-fields": "",
         "generate-test": False,
         "head-as-boolean": True,
         "keep-version-file": False,

packages/http-client-python/generator/pygen/codegen/serializers/general_serializer.py

@@ -66,7 +66,26 @@ def _update_version_map(self, version_map: dict[str, str], dep_name: str, dep: s
         if dep_version > default_version:
             version_map[dep_name] = str(dep_version)
 
-    def external_lib_version_map(self, file_content: str, additional_version_map: dict[str, str]) -> dict:
+    # Project-level pyproject.toml fields that may be preserved across regeneration
+    # via the "keep-pyproject-fields" option.
+    KEEPABLE_PROJECT_FIELDS = ("authors", "description", "classifiers", "urls")
+
+    @staticmethod
+    def _parse_keep_pyproject_fields(value: Any) -> tuple[str, ...]:
+        # The "keep-pyproject-fields" option may be a comma-separated string (e.g.
+        # "authors,description") or an already-parsed sequence of field names.
+        if not value:
+            return ()
+        if isinstance(value, str):
+            return tuple(field.strip() for field in value.split(",") if field.strip())
+        return tuple(value)
+
+    def external_lib_version_map(
+        self,
+        file_content: str,
+        additional_version_map: dict[str, str],
+        keep_pyproject_fields: tuple[str, ...] = (),
+    ) -> dict:
         # Load the pyproject.toml file if it exists and extract fields to keep.
         result: dict = {"KEEP_FIELDS": {}}
         try:
@@ -85,6 +104,14 @@ def external_lib_version_map(self, file_content: str, additional_version_map: di
 
         # Process dependencies
         if "project" in loaded_pyproject_toml:
+            project = loaded_pyproject_toml["project"]
+
+            # Keep manually customized project fields the emitter would otherwise overwrite.
+            # Only the fields explicitly listed in the "keep-pyproject-fields" option are preserved.
+            for field in keep_pyproject_fields:
+                if field in self.KEEPABLE_PROJECT_FIELDS and field in project:
+                    result["KEEP_FIELDS"][f"project.{field}"] = project[field]
+
             # Handle main dependencies
             if "dependencies" in loaded_pyproject_toml["project"]:
                 kept_deps = []
@@ -127,7 +154,10 @@ def serialize_package_file(self, template_name: str, file_content: str, **kwargs
 
         # Add fields to keep from an existing pyproject.toml
         if template_name == "pyproject.toml.jinja2":
-            params = self.external_lib_version_map(file_content, additional_version_map)
+            keep_pyproject_fields = self._parse_keep_pyproject_fields(
+                self.code_model.options.get("keep-pyproject-fields")
+            )
+            params = self.external_lib_version_map(file_content, additional_version_map, keep_pyproject_fields)
         else:
             params = {}
 

packages/http-client-python/generator/pygen/codegen/templates/packaging_templates/pyproject.toml.jinja2

@@ -11,15 +11,32 @@ build-backend = "setuptools.build_meta"
 [project]
 name = "{{ options.get('package-name')|lower }}"
 {% if options.get('package-mode') %}
+{% if KEEP_FIELDS and KEEP_FIELDS.get('project.authors') %}
+authors = [
+  {% for author in KEEP_FIELDS.get('project.authors') %}
+  { {% for key, val in author.items() %}{{ key }} = {{ val|tojson }}{% if not loop.last %}, {% endif %}{% endfor %} },
+  {% endfor %}
+]
+{% else %}
 authors = [
   { name = "{{ code_model.company_name }}"{% if code_model.is_azure_flavor %}, email = "azpysdkhelp@microsoft.com"{% endif %} },
 ]
-{% if options.get("azure-arm") %}
+{% endif %}
+{% if KEEP_FIELDS and KEEP_FIELDS.get('project.description') %}
+description = {{ KEEP_FIELDS.get('project.description')|tojson }}
+{% elif options.get("azure-arm") %}
 description = "Microsoft Azure {{ options.get('package-pprint-name') }} Client Library for Python"
 {% else %}
 description = "{{ code_model.company_name }} {% if code_model.is_azure_flavor and not options.get('package-pprint-name').startswith('Azure ') %}Azure {% endif %}{{ options.get('package-pprint-name') }} Client Library for Python"
 {% endif %}
 license = "MIT"
+{% if KEEP_FIELDS and KEEP_FIELDS.get('project.classifiers') %}
+classifiers = [
+    {% for classifier in KEEP_FIELDS.get('project.classifiers') %}
+    {{ classifier|tojson }},
+    {% endfor %}
+]
+{% else %}
 classifiers = [
     "Development Status :: {{ dev_status }}",
     "Programming Language :: Python",
@@ -29,10 +46,15 @@ classifiers = [
     "Programming Language :: Python :: 3.{{ version }}",
     {% endfor %}
 ]
+{% endif %}
 requires-python = ">={{ MIN_PYTHON_VERSION }}"
 {% else %}
+{% if KEEP_FIELDS and KEEP_FIELDS.get('project.description') %}
+description = {{ KEEP_FIELDS.get('project.description')|tojson }}
+{% else %}
 description = "{{ options.get('package-name') }}"
 {% endif %}
+{% endif %}
 {% if code_model.is_azure_flavor %}
 keywords = ["azure", "azure sdk"]
 {% endif %}
@@ -77,7 +99,13 @@ version = "{{ options.get("package-version", "unknown") }}"
 ]
 {% endfor %}
 {% endif %}
-{% if code_model.is_azure_flavor %}
+{% if KEEP_FIELDS and KEEP_FIELDS.get('project.urls') %}
+
+[project.urls]
+{% for key, val in KEEP_FIELDS.get('project.urls').items() %}
+{{ key }} = {{ val|tojson }}
+{% endfor %}
+{% elif code_model.is_azure_flavor %}
 
 [project.urls]
 repository = "https://github.com/Azure/azure-sdk-for-python"