WIP feat: contractLoader

[tabaktoni]

Motivation and Resolution

✅ Loading from directory
✅ Loading from sierra file
✅ Loading from casm file
✅ Error handling for missing sierra
✅ Sierra-only contracts (no casm)
✅ Integration with Contract class and declare

Implementation Details

• Node.js only: Uses fs/path modules, not available in browsers
• Browser stub: Provides helpful error message in browser builds
• Build configuration: Uses esbuild plugin to swap Node/browser implementations
• Name-based matching: Finds complementary files by basename (e.g., contract.sierra.json → contract.casm)
• Error handling: Clear errors for missing sierra files or multiple matches

Checklist:

• Performed a self-review of the code
• Rebased to the last commit of the target branch (or merged it into my branch)
• Linked the issues which this PR resolves
• Documented the changes in code (API docs will be generated automatically)
• Updated the tests
• All tests are passing

[tabaktoni]

@penovicp, Please take a look at this implementation

[tabaktoni]

Final idea is to enable simple loading of a contract file, extending the contract to internal use contractLoader if path('pring') is provided:

      const erc20 = await Contract.factory({
        contract: './__mocks__/cairo/cairo294',
        account,
        constructorCalldata: erc20Constructor,
      });

[penovicp]

Note that the browser platform setting is only used for the iife build. I believe that most usages of starknet.js in the browser happen by bundling the esm (or cjs) build within an application. With the node specific imports being dynamic, I surmise that most users wouldn't encounter the graceful platform compatibility error but a reference error for require.

I suggest trying a different approach. Maybe something like if (typeof require === 'undefined') throw graceful error; at the start of the contractLoader function.