Make the main mod non-null by default

This was actually much more work than I thought it would be. Tests pass,
but I'm sure there's some regressions in here.

projects/lints/build.gradle.kts

@@ -0,0 +1,34 @@
+plugins {
+    id("cc-tweaked.kotlin-convention")
+    id("cc-tweaked.java-convention")
+}
+
+repositories {
+    maven("https://maven.minecraftforge.net") {
+        content {
+            includeGroup("net.minecraftforge")
+            includeGroup("cpw.mods")
+        }
+    }
+}
+
+dependencies {
+    implementation(libs.kotlin.stdlib)
+    implementation(libs.errorProne.api)
+    implementation(libs.nullAway)
+}
+
+tasks.test {
+    jvmArgs(
+        "--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED",
+        "--add-exports=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED",
+        "--add-exports=jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED",
+        "--add-exports=jdk.compiler/com.sun.tools.javac.model=ALL-UNNAMED",
+        "--add-exports=jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED",
+        "--add-exports=jdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED",
+        "--add-exports=jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED",
+        "--add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED",
+        "--add-opens=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED",
+        "--add-opens=jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED",
+    )
+}

projects/lints/src/main/kotlin/cc/tweaked/linter/MinecraftLibraryModel.kt

@@ -0,0 +1,38 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2022. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+package cc.tweaked.linter
+
+import com.google.common.collect.ImmutableSet
+import com.google.common.collect.ImmutableSetMultimap
+import com.uber.nullaway.LibraryModels
+import com.uber.nullaway.LibraryModels.MethodRef.methodRef
+
+/**
+ * Extends NullAway's model of Minecraft's code with a couple of extra annotations.
+ */
+class MinecraftLibraryModel : LibraryModels {
+    override fun failIfNullParameters(): ImmutableSetMultimap<LibraryModels.MethodRef, Int> = ImmutableSetMultimap.of()
+    override fun explicitlyNullableParameters(): ImmutableSetMultimap<LibraryModels.MethodRef, Int> =
+        ImmutableSetMultimap.of()
+
+    override fun nonNullParameters(): ImmutableSetMultimap<LibraryModels.MethodRef, Int> = ImmutableSetMultimap.of()
+    override fun nullImpliesTrueParameters(): ImmutableSetMultimap<LibraryModels.MethodRef, Int> =
+        ImmutableSetMultimap.of()
+
+    override fun nullImpliesFalseParameters(): ImmutableSetMultimap<LibraryModels.MethodRef, Int> =
+        ImmutableSetMultimap.of()
+
+    override fun nullImpliesNullParameters(): ImmutableSetMultimap<LibraryModels.MethodRef, Int> =
+        ImmutableSetMultimap.of()
+
+    override fun castToNonNullMethods(): ImmutableSetMultimap<LibraryModels.MethodRef, Int> = ImmutableSetMultimap.of()
+    override fun nullableReturns(): ImmutableSet<LibraryModels.MethodRef> = ImmutableSet.of()
+
+    override fun nonNullReturns(): ImmutableSet<LibraryModels.MethodRef> = ImmutableSet.of(
+        // Reasoning about nullability of BlockEntity.getLevel() is awkward. For now, assume it's non-null.
+        methodRef("net.minecraft.world.level.block.entity.BlockEntity", "getLevel()"),
+    )
+}

projects/lints/src/main/resources/META-INF/services/com.uber.nullaway.LibraryModels

@@ -0,0 +1 @@
+cc.tweaked.linter.MinecraftLibraryModel