Add inspection and quick fix for unused local variables

Author: waleedyaseen

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- Add inspection and quick fix for unused local variables.
+
 ## [1.5.0] - 2023-11-27
 
 ### Added

src/main/kotlin/io/runescript/plugin/ide/inspections/RuneScriptUnusedLocalVariableInspection.kt

@@ -0,0 +1,30 @@
+package io.runescript.plugin.ide.inspections
+
+import com.intellij.codeInspection.LocalInspectionTool
+import com.intellij.codeInspection.ProblemHighlightType
+import com.intellij.codeInspection.ProblemsHolder
+import com.intellij.psi.PsiElementVisitor
+import com.intellij.psi.search.GlobalSearchScope
+import com.intellij.psi.search.searches.ReferencesSearch
+import io.runescript.plugin.ide.inspections.fixes.RsDeleteLocalVariableFix
+import io.runescript.plugin.lang.psi.RsLocalVariableDeclarationStatement
+import io.runescript.plugin.lang.psi.RsVisitor
+
+class RuneScriptUnusedLocalVariableInspection : LocalInspectionTool() {
+
+    override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean): PsiElementVisitor {
+        return object : RsVisitor() {
+            override fun visitLocalVariableDeclarationStatement(o: RsLocalVariableDeclarationStatement) {
+                val expr = o.expressionList[0]
+                val references = ReferencesSearch.search(expr, GlobalSearchScope.fileScope(expr.containingFile)).findAll()
+                if (references.isEmpty()) {
+                    holder.registerProblem(o,
+                            "Unused local variable",
+                            ProblemHighlightType.LIKE_UNUSED_SYMBOL,
+                            RsDeleteLocalVariableFix()
+                    )
+                }
+            }
+        }
+    }
+}

src/main/kotlin/io/runescript/plugin/ide/inspections/fixes/RsDeleteLocalVariableFix.kt

@@ -0,0 +1,44 @@
+package io.runescript.plugin.ide.inspections.fixes
+
+import com.intellij.codeInspection.LocalQuickFix
+import com.intellij.codeInspection.ProblemDescriptor
+import com.intellij.openapi.project.Project
+import io.runescript.plugin.lang.psi.*
+import io.runescript.plugin.symbollang.psi.RsSymSymbol
+
+class RsDeleteLocalVariableFix : LocalQuickFix {
+    override fun getFamilyName(): String = "Delete local variable"
+
+    override fun applyFix(project: Project, previewDescriptor: ProblemDescriptor) {
+        if (previewDescriptor.psiElement is RsLocalVariableDeclarationStatement) {
+            val decl = previewDescriptor.psiElement as RsLocalVariableDeclarationStatement
+            val expr = decl.expressionList.getOrNull(1)
+            if (expr == null || expr.isSimpleToRemove()) {
+                decl.delete()
+            } else {
+                val stmt = RsElementGenerator.createExpressionStatement(project, expr.text)
+                decl.replace(stmt)
+            }
+        }
+    }
+}
+
+private fun RsExpression.isSimpleToRemove(): Boolean {
+    return when (this) {
+        is RsNullLiteralExpression,
+        is RsIntegerLiteralExpression,
+        is RsCoordLiteralExpression,
+        is RsBooleanLiteralExpression,
+        is RsLongLiteralExpression -> true
+
+        is RsParExpression -> expression.isSimpleToRemove()
+        is RsCalcExpression -> expression.isSimpleToRemove()
+        is RsBinaryExpression -> left.isSimpleToRemove() && right.isSimpleToRemove()
+        is RsDynamicExpression -> {
+            val reference = reference?.resolve() ?: return false
+            return reference is RsSymSymbol
+        }
+
+        else -> false
+    }
+}

src/main/kotlin/io/runescript/plugin/lang/psi/RsElementGenerator.kt

@@ -57,6 +57,11 @@ object RsElementGenerator {
         return element.findDescendantOfType<RsDocLink>()!!.firstChild.nextSibling
     }
 
+    fun createExpressionStatement(project: Project, text: String): RsExpressionStatement {
+        val element = createDummyFile(project, "[proc,dummy]()()$text;")
+        return PsiTreeUtil.findChildOfType(element, RsExpressionStatement::class.java) as RsExpressionStatement
+    }
+
     private fun createDummyFile(project: Project, text: String): PsiFile {
         val factory = PsiFileFactory.getInstance(project) as PsiFileFactoryImpl
         val name = "dummy.${RsFileType.defaultExtension}"

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

@@ -54,6 +54,12 @@
                          enabledByDefault="true"
                          level="WARNING"
                          implementationClass="io.runescript.plugin.ide.inspections.RuneScriptUnreachableCodeInspection"/>
+        <localInspection language="RuneScript"
+                         groupName="RuneScript"
+                         displayName="Unused local variable"
+                         enabledByDefault="true"
+                         level="WARNING"
+                         implementationClass="io.runescript.plugin.ide.inspections.RuneScriptUnusedLocalVariableInspection"/>
         <localInspection language="RuneScript"
                          groupName="RuneScript"
                          displayName="Missing script symbol"

src/main/resources/inspectionDescriptions/RuneScriptUnusedLocalVariable.html

@@ -0,0 +1,5 @@
+<html>
+<body>
+<p>Reports when a local variable is unused.</p>
+</body>
+</html>