[Java] Add PlatformDetector for runtime classifier selection

[Copilot]

This PR implements task 4.2 of the Java embedded-runtime plan by adding a pure-Java platform detection utility that resolves os, arch, and Linux libc into the runtime classifier used to locate runtime.node. It also adds focused unit coverage for supported classifier resolution and fail-fast behavior on unsupported tuples.

• Platform detection utility (com.github.copilot.ffi.PlatformDetector)

  • Added detectOs() mapping os.name to darwin | linux | win32.
  • Added detectArch() mapping os.arch aliases to x64 | arm64.
  • Added detectLinuxLibc() with ELF PT_INTERP parsing from /proc/self/exe (first 2KB):
    • "/ld-musl-" → MUSL
    • "/ld-linux-" → GLIBC
    • read/parse failure → UNKNOWN
  • Added table-driven detectClassifier() and allow-list enforcement for the 8 ADR-007 classifiers.

• Classifier policy and fail-fast behavior

  • Non-Linux: <os>-<arch>
  • Linux + musl: linuxmusl-<arch>
  • Linux + glibc/unknown: linux-<arch>
  • Unsupported tuples throw immediately with a descriptive IllegalStateException.

• Unit coverage (PlatformDetectorTest)

  • Added tests for OS/arch alias mapping (success + unsupported inputs).
  • Added ELF probe fixtures for glibc and musl PT_INTERP paths.
  • Added allow-list coverage for all 8 supported classifiers.
  • Added explicit unsupported-tuple and parse-failure edge-case assertions.

String os = PlatformDetector.detectOs();          // darwin | linux | win32
String arch = PlatformDetector.detectArch();      // x64 | arm64
PlatformDetector.LinuxLibc libc = PlatformDetector.detectLinuxLibc();
String classifier = PlatformDetector.detectClassifier(); // e.g. linux-x64

• Fixes [Java] Embed Rust CLI runtime 4.2: Platform detection utility #2168

[Copilot]

🟡 Not ready to approve

Malformed ELF metadata can bypass the fallback, and one test fails incorrectly on musl hosts.

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Pull request overview

Adds Java platform detection for selecting embedded native runtime classifiers.

Changes:

• Maps OS, architecture, and Linux libc to eight supported classifiers.
• Parses ELF PT_INTERP and adds focused unit coverage.

File summaries

File	Description
PlatformDetector.java	Implements platform, libc, and classifier detection.
PlatformDetectorTest.java	Tests mappings, ELF parsing, and unsupported platforms.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 2
• Review effort level: Medium

We're testing this review assessment. Please use 👍 or 👎 to tell us if it's correct.

[github-actions]

Cross-SDK Consistency Review ✅

This PR adds PlatformDetector — a Java-internal utility for resolving the platform classifier used to locate the embedded runtime.node binary (part of the Java embedded-runtime plan, ADR-007).

Scope of change: Two new files, both under java/sdk/:

• com/github/copilot/ffi/PlatformDetector.java (added)
• com/github/copilot/ffi/PlatformDetectorTest.java (added)

No cross-SDK consistency issues found. This change is Java-specific infrastructure for embedding the Rust CLI runtime — a capability that does not exist in other language SDKs at the public API level. The other SDKs (Node.js, Python, Go, .NET, Rust) use different mechanisms to locate the CLI binary and do not need equivalent PlatformDetector utilities. No public SDK API surface was added or modified.

Generated by SDK Consistency Review Agent for #2173 · sonnet46 17.2 AIC · ⌖ 5.36 AIC · ⊞ 6.6K · ◷

[Copilot]

🟢 Ready to approve

The implementation matches the documented classifier policy and includes focused coverage for supported and malformed inputs.

This review doesn't count toward merge requirements. Sign up for the private preview to control whether Copilot approvals count.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0 new
• Review effort level: Medium

We're testing this review assessment. Please use 👍 or 👎 to tell us if it's correct.