Add mention of CORERUN_IN_BROWSER variable

[MichalStrehovsky]

The puzzle was missing a piece.

I also moved the paragraph about copying files since it needs to happen before dotnet-serve.

Cc @pavelsavara @radekdoulik

[Copilot]

Pull request overview

Updates the CoreCLR WebAssembly build/run documentation to cover the missing CORERUN_IN_BROWSER toggle and to reorder steps so required file copying happens before serving the output directory.

Changes:

• Document enabling the browser workflow by setting CORERUN_IN_BROWSER in corerun’s CMake configuration.
• Move the “populate WASM_PRELOAD_DIR / copy IL assets” guidance earlier so it occurs before dotnet-serve.
• Clarify that corerun.html is the browser entry point and may be missing if the browser workflow wasn’t enabled.

[github-actions]

🤖 Copilot Code Review — PR #126143

Note

This review was generated by GitHub Copilot.

Holistic Assessment

Motivation: Justified. The CORERUN_IN_BROWSER CMake variable defaults to 0, meaning the browser workflow won't produce corerun.html unless explicitly enabled — but the previous documentation never mentioned this prerequisite. A developer following the "Browser Testing" section would hit a confusing failure.

Approach: Sound. The change front-loads the CORERUN_IN_BROWSER prerequisite before the dotnet-serve usage instructions, and moves the WASM_PRELOAD_DIR paragraph earlier so the steps follow a logical "configure → populate → serve" order. The added note about corerun.html being the entry point further improves discoverability.

Summary: ✅ LGTM. This is a small, focused documentation improvement. The factual claims are accurate (verified CORERUN_IN_BROWSER defaults to 0 at line 5 of src/coreclr/hosts/corerun/CMakeLists.txt and WASM_PRELOAD_DIR at line 101). No code changes, no API surface changes, no trailing whitespace issues. The reorganization improves the reader experience by placing prerequisites before usage instructions.

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Detailed Findings

✅ Accuracy — Variable references verified

Both CORERUN_IN_BROWSER (line 5, defaults to 0) and WASM_PRELOAD_DIR (line 101) exist in src/coreclr/hosts/corerun/CMakeLists.txt exactly as described. The instruction to "set the CORERUN_IN_BROWSER variable to 1" is correct.

✅ Structure — Improved logical flow

Moving prerequisites (CORERUN_IN_BROWSER, WASM_PRELOAD_DIR population) above the dotnet-serve instructions puts them in the correct order for someone following the guide step-by-step. Previously, a reader would start dotnet-serve only to discover afterwards that the necessary files weren't generated.

✅ Formatting — Clean markdown

No trailing whitespace, proper blank-line separation between paragraphs, backtick formatting for variable names and file paths is consistent with the rest of the document.

Generated by Code Review for issue #126143 · ◷