Null Safety Coding Conventions Training

Key things the skill must make very clear:

• Never use @SuppressWarnings("NullAway") — this is the single most important rule
• Every package needs package-info.java with @NullMarked
• Only use org.jspecify.annotations.Nullable — not javax, jetbrains, findbugs, etc.
• @NonNull is redundant under @NullMarked — don't use it
• Every nullable access must be guarded

Step 2: Validate with test cases

After regenerating, validate the skill using the test cases in evals/evals.json.

For each test case, spawn a subagent that:

1. Reads the generated skill from plugins/conventions/skills/null-safety-coding-conventions/SKILL.md
2. Reads any input files specified in the test case
3. Completes the task described in the prompt, following the skill's conventions
4. Writes output Java files to a workspace directory

Then run the shared grading script against the outputs:

cd plugins/training
python -m shared.grade <workspace-dir>

The script checks:

• No @SuppressWarnings("NullAway")
• @NullMarked in package-info.java
• @Nullable from JSpecify on nullable references
• Null-safe handling of nullable values
• No redundant @NonNull

Test cases

1. Refactor UserService — has @SuppressWarnings("NullAway"), no package-info.java, unsafe null handling
2. Refactor ProductCatalog — uses wrong @Nullable import (javax.annotation), missing package-info.java, returns null
3. Greenfield NotificationDispatcher — new class with nullable fields, needs full null-safety setup

Input files for refactoring tests are in evals/files/.

Conventions reference

The authoritative conventions are in references/conventions.md.