Don't include package import context if pth files compat flag is set

[hoodmane]

Instead we'll get them from workers-runtime-sdk

[ask-bonk]

Now I have a clear picture. Let me analyze the key issue:

In lib.ts line 15, entropyImportContextPackages is imported unconditionally at the top level:

import { default as entropyImportContextPackages } from 'pyodide-internal:topLevelEntropy/entropy_import_context_packages.py';

But it's only used conditionally at line 100-104 (when !PROCESS_PTH_FILES). When PROCESS_PTH_FILES is true, the import is unused — the module is still loaded and its content read, even though it's never mounted to the filesystem.

The Python side handles this by wrapping the import in a try/except ImportError, which correctly handles the case where the file isn't mounted. But the TypeScript side still unconditionally imports the module. This means the module content is still being loaded/bundled even when it won't be used.

However, this is a builtin module import (pyodide-internal:...), not a dynamic file read — it's being bundled into the worker at build time. So the import will always succeed (it's compiled-in), but the data just won't be used when the flag is on. This isn't really a bug — it's just a minor inefficiency (unused import). In the context of how these builtin modules work, this is unlikely to cause errors.

Let me verify there are no other issues:

1. Compat flag change: Adding $compatEnableDate("2026-05-26") to an existing flag — this is just setting the date when it becomes default. This is a standard, safe operation.

2. Python try/except: The try/except ImportError is correctly placed and the comment explains why.

3. TypeScript conditional mount: The if (!PROCESS_PTH_FILES) check correctly skips mounting when the flag is on.

The only potential issue is the unconditional import on line 15 of lib.ts. When PROCESS_PTH_FILES is true, the file entropy_import_context_packages.py won't be written to the filesystem, but the import at line 15 will still load the raw module content into memory. This is wasted memory/work but shouldn't cause a runtime error since it's a builtin module.

Actually, let me reconsider — if the flag is on, will this builtin module still be available? These are embedded at build time, so yes. This is a minor inefficiency, not a bug.

This is a clean, small PR. The logic is correct. The only observation is the unconditional import at line 15 being a minor waste when the flag is enabled, but that's not actionable in the module system being used here (ES module imports are static and can't be conditional).

LGTM

github run

[codspeed-hq]

Merging this PR will not alter performance

✅ 72 untouched benchmarks
⏩ 129 skipped benchmarks¹

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_{Comparing hoodmane/no-package-entropy-import-context-if-pth-files-on (26ab238) with main (d092243)}

Footnotes

1. 129 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩