Make referenced optional Python RPC requests omittable

[kondv]

Fixes #1946

Problem

account.getQuota declares its params as a $ref to AccountGetQuotaRequest, and that referenced definition already carries the optional-request wrapper anyOf: [{ not: {} }, { ... }]. The Python generator's optional-params check only inspected the unresolved $ref, so it never saw the wrapper and emitted a required parameter:

result = await client.rpc.account.get_quota()
# TypeError: ServerAccountApi.get_quota() missing 1 required positional argument: 'params'

Callers had no values to supply, so the only workaround was to pass an empty request object.

Change

Resolve the params schema before the existing wrapper check, so a wrapper reached through a $ref is detected exactly like an inline one.

This corrects the five methods whose requests are declared that way — models.list, account.getQuota, plugins.marketplaces.refresh, sessions.list, and sessions.stopRemoteControl — and updates the Python quota example that documented the workaround.

The change is limited to that lookup. It adds no dependency and no general schema-validity inference, and it does not alter required requests, required-nullable fields, dataclass defaults, or how a supplied request is serialized. Other language generators are untouched.

Validation

• npm run generate:python, rerun to confirm byte-identical output
• python/test_rpc_generated.py — 12 passing; full Python unit suite — 407 passing
• nodejs npm run typecheck; shared-codegen, typescript-codegen, client-api-codegen — 28 passing
• ruff check and ruff format --check
• Live A/B against the real Copilot CLI 1.0.83, using wheels built from each tree and installed into separate clean virtual environments outside the repository:
  • Unpatched main raised ServerAccountApi.get_quota() missing 1 required positional argument: 'params', matching the report.
  • The patched wheel returned real quota snapshots for chat, completions, and premium_interactions.
  • Controls in both arms: an explicit AccountGetQuotaRequest() still succeeded, and required-params account.login still rejected omission.

[Copilot]

🟡 Changes recommended

Two moderate required-null handling issues remain unresolved in Python code generation.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Enables omission of Python RPC request objects when allowed by the original schema while preserving required nullable fields.

Changes:

• Adds draft-2019-09 schema validation for request optionality.
• Regenerates Python RPC APIs and adds regression tests.
• Updates dependencies and quota documentation.

File summaries

File	Review
scripts/codegen/python.ts	Two moderate issues: required nulls are dropped in optional session requests, and required opaque-JSON fields remain optional.
scripts/codegen/package.json	Adds AJV dependency.
scripts/codegen/package-lock.json	Locks codegen dependencies.
python/test_rpc_generated.py	Adds generated signature and serialization tests.
python/copilot/generated/rpc.py	Updates generated Python RPC models and methods.
nodejs/test/python-codegen.test.ts	Tests schema evaluation and code generation.
nodejs/package.json	Adds AJV for codegen tests.
nodejs/package-lock.json	Locks test dependencies.
docs/features/usage-and-billing.md	Documents argument-free quota retrieval.

Review details

Files not reviewed (2)

• nodejs/package-lock.json: Generated file
• scripts/codegen/package-lock.json: Generated file

Suppressed comments (1)

scripts/codegen/python.ts:3957

• The server-method path has the same optional-wrapper/required-nullable interaction: filtering None here drops a required field when the request object is supplied explicitly. Select params.to_dict() when preserveRequiredNulls is true, while retaining {} for an omitted request.

            if (paramsOptional) {
                lines.push(`        params_dict = {k: v for k, v in params.to_dict().items() if v is not None} if params is not None else {}`);
            } else if (preserveRequiredNulls) {
                lines.push(`        params_dict = params.to_dict()`);

• Files reviewed: 6/9 changed files
• Comments generated: 2
• Review effort level: Balanced

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[Copilot]

🟢 Approval recommended

The focused generator fix is covered by regression tests with no unresolved issues.

Review details

• Files reviewed: 3/4 changed files
• Comments generated: 0 new
• Review effort level: Balanced