Merge pull request github#85 from github/igfoo/companion

Kotlin: Add support for companion objects

Author: igfoo

java/kotlin-extractor/src/main/kotlin/KotlinExtractorExtension.kt

@@ -622,6 +622,9 @@ class X {
         }
     }
 
+    /*
+    This returns the `X` in c's label `@"class;X"`.
+    */
     private fun getUnquotedClassLabel(c: IrClass, typeArgs: List<IrTypeArgument>): String {
         val pkg = c.packageFqName?.asString() ?: ""
         val cls = c.name.asString()
@@ -876,6 +879,28 @@ open class KotlinFileExtractor(
         val locId = tw.getLocation(c)
         tw.writeHasLocation(id, locId)
 
+        val parent = c.parent
+        if (parent is IrClass) {
+            val parentId = useClassInstance(parent, listOf()).classLabel
+            tw.writeEnclInReftype(id, parentId)
+            if(c.isCompanion) {
+                // If we are a companion then our parent has a
+                //     public static final ParentClass$CompanionObjectClass CompanionObJectName;
+                // that we need to fabricate here
+                val instance = useCompanionObjectClassInstance(c)
+                if(instance != null) {
+                    val type = useSimpleTypeClass(c, emptyList(), false)
+                    tw.writeFields(instance.id, instance.name, type.javaResult.id, type.kotlinResult.id, id, instance.id)
+                    tw.writeHasLocation(instance.id, locId)
+                    tw.writeHasModifier(instance.id, extractModifier("public"))
+                    tw.writeHasModifier(instance.id, extractModifier("static"))
+                    tw.writeHasModifier(instance.id, extractModifier("final"))
+                    @Suppress("UNCHECKED_CAST")
+                    tw.writeClass_companion_object(parentId as Label<DbClass>, instance.id, id as Label<DbClass>)
+                }
+            }
+        }
+
         c.typeParameters.map { extractTypeParameter(it) }
         c.declarations.map { extractDeclaration(it, id) }
         extractObjectInitializerFunction(c, id)
@@ -901,16 +926,35 @@ open class KotlinFileExtractor(
         return id
     }
 
-    data class ObjectClassInstance(val id: Label<DbField>, val name: String)
-    fun useObjectClassInstance(c: IrClass): ObjectClassInstance {
+    data class FieldResult(val id: Label<DbField>, val name: String)
+
+    fun useCompanionObjectClassInstance(c: IrClass): FieldResult? {
+        val parent = c.parent
+        if(!c.isCompanion) {
+            logger.warn(Severity.ErrorSevere, "Using companion instance for non-companion class")
+            return null
+        }
+        else if (parent !is IrClass) {
+            logger.warn(Severity.ErrorSevere, "Using companion instance for non-companion class")
+            return null
+        } else {
+            val parentId = useClassInstance(parent, listOf()).classLabel
+            val instanceName = c.name.asString()
+            val instanceLabel = "@\"field;{$parentId};$instanceName\""
+            val instanceId: Label<DbField> = tw.getLabelFor(instanceLabel)
+            return FieldResult(instanceId, instanceName)
+        }
+    }
+
+    fun useObjectClassInstance(c: IrClass): FieldResult {
         if(!c.isNonCompanionObject) {
             logger.warn(Severity.ErrorSevere, "Using instance for non-object class")
         }
         val classId = useClassInstance(c, listOf()).classLabel
         val instanceName = "INSTANCE"
         val instanceLabel = "@\"field;{$classId};$instanceName\""
         val instanceId: Label<DbField> = tw.getLabelFor(instanceLabel)
-        return ObjectClassInstance(instanceId, instanceName)
+        return FieldResult(instanceId, instanceName)
     }
 
     private fun isQualifiedThis(vp: IrValueParameter): Boolean {
@@ -1657,15 +1701,17 @@ open class KotlinFileExtractor(
                 // field that we are accessing here.
                 val exprParent = parent.expr(e, callable)
                 val c: IrClass = e.symbol.owner
-                val instance = useObjectClassInstance(c)
+                val instance = if (c.isCompanion) useCompanionObjectClassInstance(c) else useObjectClassInstance(c)
 
-                val id = tw.getFreshIdLabel<DbVaraccess>()
-                val type = useType(e.type)
-                val locId = tw.getLocation(e)
-                tw.writeExprs_varaccess(id, type.javaResult.id, type.kotlinResult.id, exprParent.parent, exprParent.idx)
-                tw.writeHasLocation(id, locId)
+                if(instance != null) {
+                    val id = tw.getFreshIdLabel<DbVaraccess>()
+                    val type = useType(e.type)
+                    val locId = tw.getLocation(e)
+                    tw.writeExprs_varaccess(id, type.javaResult.id, type.kotlinResult.id, exprParent.parent, exprParent.idx)
+                    tw.writeHasLocation(id, locId)
 
-                tw.writeVariableBinding(id, instance.id)
+                    tw.writeVariableBinding(id, instance.id)
+                }
             }
             else -> {
                 logger.warnElement(Severity.ErrorSevere, "Unrecognised IrExpression: " + e.javaClass, e)

java/ql/lib/config/semmlecode.dbscheme

@@ -319,6 +319,12 @@ class_object(
   unique int instance: @field ref
 );
 
+class_companion_object(
+  unique int id: @class ref,
+  unique int instance: @field ref,
+  unique int companion_object: @class ref
+);
+
 kt_nullable_types(
   unique int id: @kt_nullable_type,
   int classid: @classorinterface ref

java/ql/lib/semmle/code/java/Type.qll

@@ -647,6 +647,11 @@ class Class extends ClassOrInterface, @class {
     )
   }
 
+  /** Get the companion object of this class, if any. */
+  ClassCompanionObject getCompanionObject() {
+    class_companion_object(this, _, result)
+  }
+
   override string getAPrimaryQlClass() { result = "Class" }
 }
 
@@ -662,6 +667,18 @@ class ClassObject extends Class {
   }
 }
 
+/** A Kotlin `companion object`. */
+class ClassCompanionObject extends Class {
+  ClassCompanionObject() {
+    class_companion_object(_, _, this)
+  }
+
+  /** Gets the instance variable that implements this `companion object`. */
+  Field getInstance() {
+    class_companion_object(_, result, this)
+  }
+}
+
 /**
  * A record declaration.
  */

java/ql/test/kotlin/library-tests/companion_objects/accesses.expected

@@ -0,0 +1 @@
+| companion_objects.kt:3:5:5:5 | MyClassCompanion | companion_objects.kt:9:5:9:11 | MyClassCompanion |

java/ql/test/kotlin/library-tests/companion_objects/accesses.ql

@@ -0,0 +1,5 @@
+import java
+
+from VarAccess va, ClassCompanionObject cco
+where va.getVariable() = cco.getInstance()
+select cco, va

java/ql/test/kotlin/library-tests/companion_objects/companion_objects.expected

@@ -0,0 +1 @@
+| companion_objects.kt:1:1:6:1 | MyClass | companion_objects.kt:3:5:5:5 | MyClassCompanion | companion_objects.kt:3:5:5:5 | MyClassCompanion | final,public,static |

java/ql/test/kotlin/library-tests/companion_objects/companion_objects.kt

@@ -0,0 +1,12 @@
+class MyClass {
+    fun funInClass() {}
+    companion object MyClassCompanion {
+        fun funInCompanion() {}
+    }
+}
+
+fun user() {
+    MyClass.funInCompanion()
+    MyClass().funInClass()
+}
+

java/ql/test/kotlin/library-tests/companion_objects/companion_objects.ql

@@ -0,0 +1,7 @@
+import java
+
+from Class c, ClassCompanionObject cco, Field f
+where c.fromSource()
+  and cco = c.getCompanionObject()
+  and f = cco.getInstance()
+select c, f, cco, concat(f.getAModifier().toString(), ",")

java/ql/test/kotlin/library-tests/object/accesses.ql

@@ -3,6 +3,3 @@ import java
 from VarAccess va, ClassObject co
 where va.getVariable() = co.getInstance()
 select co, va
-
-// select count(VarAccess va)
-