download_jdk gclient var is declared but never consumed in DEPS (no-op) #187627

Summary

The download_jdk gclient var declared at DEPS:97 is vestigial — no DEPS entry references it as a condition, so setting it has no effect on what gets synced. Multiple builder configs in engine/src/flutter/ci/builders/*.json set "download_jdk": false expecting to skip the OpenJDK download, but it's a no-op.

Steps to reproduce

# In a fresh gclient checkout of flutter
cat > .gclient <<'EOF'
solutions = [{
  "managed": False,
  "name": ".",
  "url": "https://github.com/flutter/flutter.git",
  "deps_file": "DEPS",
  "custom_vars": {"download_jdk": False},
}]
EOF

gclient sync --no-history --shallow -j8

# OpenJDK is downloaded anyway:
ls engine/src/flutter/third_party/java/openjdk/bin/java
# → file exists on linux-x64 / mac / win regardless of download_jdk

Why

DEPS:97 declares it with comment "Checkout Java dependencies only on platforms that do not have java installed on path":

'download_jdk': True,

But the engine/src/flutter/third_party/java/openjdk dep block (the only OpenJDK CIPD entry) gates only on host_os/host_cpu:

'engine/src/flutter/third_party/java/openjdk': {
   'packages': [...],
   'condition': 'not (host_os == "linux" and host_cpu == "arm64")',
   # Always download the JDK since java is required for running the formatter.
   'dep_type': 'cipd',
},

grep download_jdk DEPS returns only the declaration on line 97 — nothing else in the file references it.

Evidence in the wild

The flag is set to false in many builder configs that expect it to skip the JDK pull:

$ grep -rln "download_jdk.*false" engine/src/flutter/ci/builders/ | head
engine/src/flutter/ci/builders/mac_clang_tidy.json          # 7 occurrences
engine/src/flutter/ci/builders/linux_web_engine_test.json
engine/src/flutter/ci/builders/mac_android_aot_engine.json
engine/src/flutter/ci/builders/mac_host_engine.json
engine/src/flutter/ci/builders/windows_arm_host_engine.json
engine/src/flutter/ci/builders/linux_host_desktop_engine.json
engine/src/flutter/ci/builders/linux_host_engine_test.json
engine/src/flutter/ci/builders/windows_host_engine.json
engine/src/flutter/ci/builders/local_engine.json
engine/src/flutter/ci/builders/linux_fuchsia.json

And recently added in linux_arm64_android_aot_engine.json (where I observed this).

Observed sync behavior across four recent gclient runs:

Suggested fixes (in order of preference)

1. Wire it up. Combine the var with the host check so download_jdk: false actually works:

   'condition': 'not (host_os == "linux" and host_cpu == "arm64") and download_jdk',

   Then sweep through the builder JSONs and remove "download_jdk": false from any that didn't actually need to skip (and keep it where the author intended to skip).

2. Remove the variable. Delete the declaration on DEPS:97 and remove download_jdk: false from every builder JSON that sets it. Documents that the OpenJDK download is unconditional except on linux-arm64.

3. Document the no-op. Add a comment to DEPS:97 saying "currently unused — kept for future re-wiring" and don't change builder configs. (Worst option — codifies the confusion.)

I'd lean toward (1) because some builders genuinely don't need the JDK (e.g. linux_arm64_android_aot_engine builds gen_snapshot which doesn't touch Java); skipping ~50 MB of CIPD per such builder is small but free.

Not a blocker

This isn't blocking #187591 or anything user-visible. The OpenJDK package is correctly excluded on linux-arm64 hosts (where it doesn't exist as a CIPD package). On linux-x64 it's just always-downloaded, which the code intends. The cleanup is cosmetic + saves a small amount of CIPD bandwidth in CI.

Where I noticed it

While running validation builds for #187591:

• 2026-06-05 linux-x64 cross-compile: download_jdk: false → OpenJDK present
• 2026-06-05 linux-arm64 native: download_jdk: false → OpenJDK absent (the host_cpu == "arm64" exclusion fires)

Compared the two sync outputs and confirmed via grep download_jdk DEPS that only the declaration exists.