feat: add backward compatibility for models.get("owner/name") syntax

[zeke]

This PR adds backward compatibility for the legacy models.get("owner/name") syntax while maintaining full forward compatibility with the new keyword argument format.

Changes

• Add compatibility layer: Created src/replicate/lib/models.py with a clean patching system that handles both legacy and new syntax
• Patch client initialization: Modified both Replicate and AsyncReplicate classes to apply the compatibility patch when the models resource is created
• Support both formats:
  • Legacy: models.get("stability-ai/stable-diffusion")
  • New: models.get(model_owner="stability-ai", model_name="stable-diffusion")
• Add tests: Created tests/test_models_backward_compat.py with 12 test cases covering both syntax formats, async/sync clients, and error handling
• Fix API consistency: Added missing api_token parameter to both sync and async copy() methods to match __init__() signature
• Reduce breaking changes: This reduces breaking changes from 4 to 3 areas, making migration easier for users with existing codebases

Details

The code uses a simple patching approach (~115 lines total):

1. _parse_model_args() helper function handles both legacy "owner/name" and new keyword argument parsing
2. patch_models_resource() wraps the original get method with backward compatibility logic
3. Works with both sync and async clients
4. Maintains all existing functionality (extra_headers, timeout, etc.)
5. Provides clear error messages for invalid formats

Fixes Applied

• Type checking: Added proper type annotations and mypy ignores for clean linting
• Test reliability: Fixed test fixtures to properly provide bearer_token instead of relying on environment mocking
• API consistency: Added missing api_token parameter to copy() methods to prevent signature mismatch errors

Testing locally

gh repo clone replicate/replicate-python-stainless
cd replicate-python-stainless
gh pr checkout 68
scripts/test tests/test_models_backward_compat.py

Resolves https://linear.app/replicate/issue/DP-656/add-backward-compatibility-for-modelsgetownername-syntax

Prompts

work on this issue: https://linear.app/replicate/issue/DP-656/add-backward-compatibility-for-modelsgetownername-syntax

can lib/models.py be simpler while still supporting the requirements? seems like a lot of code.

tests are still failing! https://github.com/replicate/replicate-python-stainless/actions/runs/17935238215/job/51000105652?pr=68

[linear]

DP-656 Add backward compatibility for models.get(\"owner/name\") syntax

Problem

The legacy replicate-python v1.x client supported this syntax:

model = replicate.models.get("stability-ai/stable-diffusion")

The new v2.x client requires separate keyword arguments:

model = replicate.models.get(
    model_owner="stability-ai", 
    model_name="stable-diffusion"
)

This is a breaking change that will require users to update their code when migrating to v2.x.

Solution

Add a compatibility layer that detects the legacy "owner/name" string format and automatically splits it into the required keyword arguments.

Implementation Notes

• Check if the first argument is a string containing "/"
• If so, split on "/" and map to model_owner/model_name parameters
• Maintain existing keyword argument behavior for new usage
• Add tests for both legacy and new syntax

Impact

This would reduce breaking changes from 4 to 3 areas, making migration easier for users with existing codebases.