Migrate Java execution from Docker to CheerpJ (browser-side) - #1
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Replaces the server-side Docker sandbox with CheerpJ 3.0, a WASM-based JVM that compiles and runs Java entirely in the browser. Students no longer consume server resources when clicking Run — zero containers, no rate limiting needed. Key changes: - Add CheerpJProvider context (loads runtime from CDN, calls cheerpjInit) - Add cheerpj-executor: writes .java files to CheerpJ VFS, invokes javac via cheerpjRunMain, captures System.out via console.log interception, parses JSON test results from TestBase.printResults() - Expose Test.java to client: add testCode field to LessonData/getLessonData - Remove auth gate on Run button — execution is now free for all users - Add POST /api/analytics/run to record code_run / exercise_complete events - Add scripts/build-cheerpj-assets.sh: compiles ftc-stubs.jar (Java 8 target) and downloads OpenJDK 8 tools.jar (contains javac) - Remove lib/docker.ts, lib/compiler.ts, app/api/execute/route.ts - Remove dockerode dependency and serverExternalPackages entry - Add Playwright browser tests (8 tests, all passing in ~56s) Timing profile: cold compile ~5s, warm compile ~1.7s, test run ~700ms. The main cost is javac lazy-loading classes from tools.jar (18MB) on first use; subsequent runs in the same session are 3x faster. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
bun test picked up the Playwright test file and crashed because test.setTimeout() is a Playwright-only API. Moving browser tests to e2e/ keeps them separate from the bun test runner. - Move tests/cheerpj-browser.test.ts → e2e/cheerpj-browser.test.ts - Add test:e2e script (playwright test e2e/) - Replace CI workflow: drop Docker sandbox build, run tsc + eslint instead (execution tests are browser-side and don't run in CI without a display) Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Summary
testCodeto client —Test.javais included inLessonDataso the browser executor can pass it to javac/CheerpJ.POST /api/analytics/runrecordscode_runandexercise_completeevents after browser-side execution completes.scripts/build-cheerpj-assets.shcompilesftc-stubs.jar(Java 8 target) and downloads OpenJDK 8tools.jar(contains javac); run withbun run build:cheerpj.Architecture
Timing profile (measured):
The main cold-start cost is javac lazy-loading classes from
tools.jar(18MB) over the network. Subsequent runs in the same session are ~3x faster.Files removed
lib/compiler.ts,lib/docker.ts— Docker orchestrationapp/api/execute/route.ts— server-side execution endpointtests/sandbox.test.ts— Docker integration tests (replaced by Playwright browser tests)Test plan
bun run build:cheerpj— verifypublic/cheerpj/ftc-stubs.jarandpublic/cheerpj/tools.jarare createdbun dev→ open a lesson → click Run with starter code → verify failing test results appear (~6s)npx playwright test tests/cheerpj-browser.test.ts— all 8 tests pass🤖 Generated with Claude Code