feat: Add findParentMethod utility method (#4)

* feat: Add `findParentMethod` utitly method

* refactor: add `resolveMethod` to `MethodResolver`

added some assertions and some tests

Co-authored-by: Lucaskyy <contact@sculas.xyz>

src/main/kotlin/net/revanced/patcher/cache/PatchData.kt

@@ -1,5 +1,7 @@
 package net.revanced.patcher.cache
 
+import net.revanced.patcher.resolver.MethodResolver
+import net.revanced.patcher.signature.Signature
 import org.objectweb.asm.tree.ClassNode
 import org.objectweb.asm.tree.MethodNode
 
@@ -7,7 +9,11 @@ data class PatchData(
     val declaringClass: ClassNode,
     val method: MethodNode,
     val scanData: PatternScanData
-)
+) {
+    fun findParentMethod(signature: Signature): PatchData? {
+       return MethodResolver.resolveMethod(declaringClass, signature)
+    }
+}
 
 data class PatternScanData(
     val startIndex: Int,

src/main/kotlin/net/revanced/patcher/resolver/MethodResolver.kt

@@ -25,7 +25,7 @@ internal class MethodResolver(private val classList: List<ClassNode>, private va
                         continue
                     }
                     logger.debug { "Resolving sig ${signature.name}: ${classNode.name} / ${method.name}" }
-                    val (r, sr) = this.cmp(method, signature)
+                    val (r, sr) = cmp(method, signature)
                     if (!r || sr == null) {
                         logger.debug { "Compare result for sig ${signature.name} has failed!" }
                         continue
@@ -52,43 +52,71 @@ internal class MethodResolver(private val classList: List<ClassNode>, private va
         return methodMap
     }
 
-    private fun cmp(method: MethodNode, signature: Signature): Pair<Boolean, ScanResult?> {
-        val returns = Type.getReturnType(method.desc).convertObject()
-        if (signature.returns != returns) {
-            logger.debug {
-                """
+    // These functions do not require the constructor values, so they can be static.
+    companion object {
+        fun resolveMethod(classNode: ClassNode, signature: Signature): PatchData? {
+            for (method in classNode.methods) {
+                val (r, sr) = cmp(method, signature, true)
+                if (!r || sr == null) continue
+                return PatchData(
+                    classNode,
+                    method,
+                    PatternScanData(0, 0) // opcode list is always ignored.
+                )
+            }
+            return null
+        }
+
+        private fun cmp(method: MethodNode, signature: Signature, search: Boolean = false): Pair<Boolean, ScanResult?> {
+            val returns = Type.getReturnType(method.desc).convertObject()
+            if (signature.returns != returns) {
+                logger.debug {
+                    """
                     Comparing sig ${signature.name}: invalid return type:
                     expected ${signature.returns}},
                     got $returns
                 """.trimIndent()
+                }
+                return false to null
             }
-            return false to null
-        }
 
-        if (signature.accessors != method.access) {
-            logger.debug { "Comparing sig ${signature.name}: invalid accessors:\nexpected ${signature.accessors},\ngot ${method.access}" }
-            return false to null
-        }
+            if (signature.accessors != method.access) {
+                logger.debug {
+                    """
+                    Comparing sig ${signature.name}: invalid accessors:
+                    expected ${signature.accessors}},
+                    got ${method.access}
+                """.trimIndent()
+                }
+                return false to null
+            }
 
-        val parameters = Type.getArgumentTypes(method.desc).convertObjects()
-        if (!signature.parameters.contentEquals(parameters)) {
-            logger.debug {
-                """
+            val parameters = Type.getArgumentTypes(method.desc).convertObjects()
+            if (!signature.parameters.contentEquals(parameters)) {
+                logger.debug {
+                    """
                     Comparing sig ${signature.name}: invalid parameter types:
                     expected ${signature.parameters.joinToString()}},
                     got ${parameters.joinToString()}
                 """.trimIndent()
+                }
+                return false to null
             }
-            return false to null
-        }
 
-        val result = method.instructions.scanFor(signature.opcodes)
-        if (!result.found) {
-            logger.debug { "Comparing sig ${signature.name}: invalid opcode pattern" }
-            return false to null
-        }
+            if (!search) {
+                if (signature.opcodes.isEmpty()) {
+                    throw IllegalArgumentException("Opcode list for signature ${signature.name} is empty. This is not allowed for non-search signatures.")
+                }
+                val result = method.instructions.scanFor(signature.opcodes)
+                if (!result.found) {
+                    logger.debug { "Comparing sig ${signature.name}: invalid opcode pattern" }
+                    return false to null
+                }
+                return true to result
+            }
 
-        return true to result
+            return true to ScanResult(true)
+        }
     }
 }
 

src/main/kotlin/net/revanced/patcher/signature/Signature.kt

@@ -10,10 +10,14 @@ import org.objectweb.asm.Type
  * If you are unable to guess a method name, doing something like "patch-name-1" is fine too.
  * For example: "override-codec-1".
  * This method name will be used to find the corresponding patch.
+ * Even though this is technically not needed for the `findParentMethod` method,
+ * it is still recommended giving the method a name, so it can be identified easily.
  * @param returns The return type/signature of the method.
  * @param accessors The accessors of the method.
  * @param parameters The parameter types of the method.
  * @param opcodes The opcode pattern of the method, used to find the method by pattern scanning.
+ * ***Only if*** **you are using **`findParentMethod`** are you allowed to specify an empty array.**
+ * This parameter will be ignored when using the `findParentMethod` method.
  */
 @Suppress("ArrayInDataClass")
 data class Signature(

src/test/kotlin/net/revanced/patcher/PatcherTest.kt

@@ -9,11 +9,13 @@ import net.revanced.patcher.util.ExtraTypes
 import net.revanced.patcher.util.TestUtil
 import net.revanced.patcher.writer.ASMWriter.insertAt
 import net.revanced.patcher.writer.ASMWriter.setAt
+import org.junit.jupiter.api.assertThrows
 import org.objectweb.asm.Opcodes.*
 import org.objectweb.asm.Type
 import org.objectweb.asm.tree.*
 import java.io.PrintStream
 import kotlin.test.Test
+import kotlin.test.assertEquals
 
 internal class PatcherTest {
     companion object {
@@ -145,4 +147,27 @@ internal class PatcherTest {
     //    out.close()
     //    testData.close()
     //}
+
+    @Test()
+    fun `should raise an exception because opcodes is empty`() {
+        val sigName = "testMethod"
+        val e = assertThrows<IllegalArgumentException>("Should raise an exception because opcodes is empty") {
+            Patcher(
+                PatcherTest::class.java.getResourceAsStream("/test1.jar")!!,
+                arrayOf(
+                    Signature(
+                        sigName,
+                        Type.VOID_TYPE,
+                        ACC_PUBLIC or ACC_STATIC,
+                        arrayOf(ExtraTypes.ArrayAny),
+                        emptyArray() // this is not allowed for non-search signatures!
+                    )
+                )
+            )
+        }
+        assertEquals(
+            "Opcode list for signature $sigName is empty. This is not allowed for non-search signatures.",
+            e.message
+        )
+    }
 }