Break java

[harshyyy21]

Description

No longer support Java versions below 21.

Scenarios Tested

Tested this with Java 11 and Java 25.

Java 11 output:

node lib/bin/firebase.js emulators:start --only firestore 
⚠  Could not find config (firebase.json) so using defaults.
⬢  emulators: firebase-tools no longer supports Java version before 21. Please install a JDK at version 21 or above to get a compatible runtime.
i  emulators: Shutting down emulators.

Error: firebase-tools no longer supports Java version before 21. Please install a JDK at version 21 or above to get a compatible runtime.

Java 25 output:

node lib/bin/firebase.js emulators:start --only firestore 
⚠  Could not find config (firebase.json) so using defaults.
i  emulators: Starting emulators: firestore
⚠  firestore: Did not find a Cloud Firestore rules file specified in a firebase.json config file.
⚠  firestore: The emulator will default to allowing all reads and writes. Learn more about this option: https://firebase.google.com/docs/emulator-suite/install_and_configure#security_rules_configuration.
i  firestore: Firestore Emulator logging to firestore-debug.log
✔  firestore: Firestore Emulator UI websocket is running on 9150.

┌─────────────────────────────────────────────────────────────┐
│ ✔  All emulators ready! It is now safe to connect your app. │
│ i  View Emulator UI at http://127.0.0.1:4000/               │
└─────────────────────────────────────────────────────────────┘

┌───────────┬────────────────┬─────────────────────────────────┐
│ Emulator  │ Host:Port      │ View in Emulator UI             │
├───────────┼────────────────┼─────────────────────────────────┤
│ Firestore │ 127.0.0.1:8080 │ http://127.0.0.1:4000/firestore │
└───────────┴────────────────┴─────────────────────────────────┘
  Emulator Hub host: 127.0.0.1 port: 4400
  Other reserved ports: 4500, 9150

Issues? Report them at https://github.com/firebase/firebase-tools/issues and attach the *-debug.log files.

[gemini-code-assist]

Summary of Changes

Hello @harshyyy21, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request implements a breaking change by enforcing a minimum Java version of 21 for running Firebase emulators. Previously, users with older Java versions would receive a warning, but the emulators might still function. With this update, any attempt to start emulators using Java versions below 21 will now trigger a critical error, preventing them from launching. This ensures that the emulator suite operates within a supported and modern Java environment.

Highlights

• Enforced Java Version: Firebase emulators now strictly require Java Development Kit (JDK) version 21 or higher to run. This change removes support for older Java versions.
• Error on Unsupported Version: Attempting to run Firebase emulators with a Java version below 21 will now result in a FirebaseError, immediately halting execution, rather than just issuing a warning.
• Updated Warning Message: The user-facing warning message (JAVA_DEPRECATION_WARNING) has been updated to clearly state that Java versions below 21 are no longer supported, reflecting the immediate breaking change.
• Changelog Entry: A new entry has been added to the CHANGELOG.md file documenting the removal of support for Java versions prior to 21 for running emulators.

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[gemini-code-assist]

Code Review

This pull request correctly enforces the minimum Java version requirement by throwing an error for versions below 21, instead of just showing a warning. The changes are logical and achieve the intended goal. I have two suggestions to improve this change. First, I recommend explicitly marking this as a breaking change in the changelog for better user visibility. Second, I've pointed out that the error message is logged twice, which is redundant, and suggested a way to clean this up for a better user experience. Overall, a solid update.