Add an inspection for when the mod id in fabric.mod.json doesn't match the mod id in the code (#2499)

src/main/kotlin/platform/fabric/inspection/ModIdMismatchInspection.kt

@@ -0,0 +1,99 @@
+/*
+ * Minecraft Development for IntelliJ
+ *
+ * https://mcdev.io/
+ *
+ * Copyright (C) 2025 minecraft-dev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, version 3.0 only.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.demonwav.mcdev.platform.fabric.inspection
+
+import com.demonwav.mcdev.util.constantStringValue
+import com.intellij.codeInspection.LocalInspectionTool
+import com.intellij.codeInspection.LocalQuickFix
+import com.intellij.codeInspection.ProblemDescriptor
+import com.intellij.codeInspection.ProblemsHolder
+import com.intellij.json.psi.JsonFile
+import com.intellij.json.psi.JsonObject
+import com.intellij.json.psi.JsonStringLiteral
+import com.intellij.openapi.project.Project
+import com.intellij.psi.JavaElementVisitor
+import com.intellij.psi.JavaPsiFacade
+import com.intellij.psi.PsiElementVisitor
+import com.intellij.psi.PsiField
+import com.intellij.psi.PsiManager
+import com.intellij.psi.search.FilenameIndex
+import com.intellij.psi.search.GlobalSearchScope
+
+class ModIdMismatchInspection : LocalInspectionTool() {
+
+    override fun getStaticDescription() = "Checks for a mismatch between the mod ID in fabric.mod.json and the java code."
+
+    override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean): PsiElementVisitor = Visitor(holder)
+
+    private class Visitor(private val holder: ProblemsHolder) : JavaElementVisitor() {
+
+        override fun visitField(field: PsiField) {
+            super.visitField(field)
+
+            if (field.name != "MOD_ID" && field.name != "MODID") return
+            val initializer = field.initializer
+            val javaModId = initializer?.constantStringValue ?: return
+
+            val project = field.project
+            val jsonModId = getModIdFromJson(project, field.manager) ?: return
+            if ('$' in jsonModId) return
+
+            if (javaModId != jsonModId) {
+                holder.registerProblem(
+                    initializer,
+                    "Mod ID '$javaModId' does not match mod ID '$jsonModId' from fabric.mod.json",
+                    ChangeFieldInitializerQuickFix(jsonModId)
+                )
+            }
+        }
+
+        private fun getModIdFromJson(project: Project, manager: PsiManager): String? {
+            val files = FilenameIndex.getVirtualFilesByName(
+                "fabric.mod.json",
+                GlobalSearchScope.projectScope(project)
+            )
+
+            val file = files.firstOrNull() ?: return null
+
+            val jsonFile = manager.findFile(file) as? JsonFile ?: return null
+            val topLevelObj = jsonFile.topLevelValue as? JsonObject ?: return null
+
+            val stringLiteral = topLevelObj.findProperty("id")?.value as? JsonStringLiteral ?: return null
+            return stringLiteral.value
+        }
+    }
+
+    private class ChangeFieldInitializerQuickFix(
+        private val newValue: String
+    ) : LocalQuickFix {
+
+        override fun getName() = "Change mod ID field to \"$newValue\""
+
+        override fun getFamilyName() = "Change mod ID field"
+
+        override fun applyFix(project: Project, descriptor: ProblemDescriptor) {
+            val initializer = descriptor.psiElement ?: return
+            val factory = JavaPsiFacade.getElementFactory(project)
+            val newInitializer = factory.createExpressionFromText("\"$newValue\"", null)
+            initializer.replace(newInitializer)
+        }
+    }
+}

src/main/resources/META-INF/plugin.xml

@@ -991,6 +991,14 @@
                          level="ERROR"
                          hasStaticDescription="true"
                          implementationClass="com.demonwav.mcdev.platform.fabric.inspection.FabricEntrypointsInspection"/>
+        <localInspection displayName="Fabric mod ID mismatch"
+                         shortName="ModIdMismatch"
+                         groupName="Fabric"
+                         language="JAVA"
+                         enabledByDefault="true"
+                         level="WARNING"
+                         hasStaticDescription="true"
+                         implementationClass="com.demonwav.mcdev.platform.fabric.inspection.ModIdMismatchInspection"/>
         <!--endregion-->
 
         <!--region MCP INSPECTIONS-->