From 547c0eb8b9675893d44d99c1ea624b8e124126cf Mon Sep 17 00:00:00 2001
From: Lars Eckart <lars.eckart@hey.com>
Date: Mon, 9 Dec 2024 20:49:27 +0200
Subject: [PATCH] - F Seam for what error is thrown from Approvals

fixes #596

Co-authored-by: Jay Bazuzi <jay@bazuzi.com>
Co-authored-by: Llewellyn Falco <llewellyn.falco@gmail.com>
---
 .../approvers/FileApproverTest.java           | 14 +++++++++
 .../org/approvaltests/ApprovalSettings.java   |  5 ++++
 .../approvaltests/approvers/FileApprover.java | 29 ++++++++++++++-----
 3 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/approvaltests-tests/src/test/java/org/approvaltests/approvers/FileApproverTest.java b/approvaltests-tests/src/test/java/org/approvaltests/approvers/FileApproverTest.java
index 0b4c817f3..2640dc611 100644
--- a/approvaltests-tests/src/test/java/org/approvaltests/approvers/FileApproverTest.java
+++ b/approvaltests-tests/src/test/java/org/approvaltests/approvers/FileApproverTest.java
@@ -4,6 +4,7 @@
 import com.spun.util.io.FileUtils;
 import com.spun.util.tests.StackTraceReflectionResult;
 import com.spun.util.tests.TestUtils;
+import org.approvaltests.ApprovalSettings;
 import org.approvaltests.Approvals;
 import org.approvaltests.core.Options;
 import org.approvaltests.core.VerifyResult;
@@ -69,4 +70,17 @@ public void testCustomApprover()
     Approvals.verify(new FileApprover(writer, namer, approveEverything));
     // end-snippet
   }
+  @Test
+  void testCustomError() throws Exception
+  {
+    var expected = """
+        java.lang.AssertionError: Custom message
+        """;
+    try (AutoCloseable old = Approvals.settings()
+        .registerErrorGenerator((received, approved) -> new AssertionError("Custom message")))
+    {
+      FileApprover fileApprover = new FileApprover(new File("a.txt"), new File("b.txt"), null, null);
+      Approvals.verifyException(fileApprover::fail, new Options().inline(expected));
+    }
+  }
 }
diff --git a/approvaltests/src/main/java/org/approvaltests/ApprovalSettings.java b/approvaltests/src/main/java/org/approvaltests/ApprovalSettings.java
index 59cb14ae0..4adfdef96 100644
--- a/approvaltests/src/main/java/org/approvaltests/ApprovalSettings.java
+++ b/approvaltests/src/main/java/org/approvaltests/ApprovalSettings.java
@@ -2,6 +2,7 @@
 
 import com.spun.util.introspection.Caller;
 import org.approvaltests.approvers.FileApprover;
+import org.lambda.functions.Function2;
 import org.lambda.query.Queryable;
 
 import java.io.File;
@@ -22,4 +23,8 @@ public void allowMultipleVerifyCallsForThisClass()
     String className = caller.getClassName().replace('.', File.separatorChar);
     FileApprover.tracker.addAllowedDuplicates(f -> f.contains(className));
   }
+  public static AutoCloseable registerErrorGenerator(Function2<String, String, Error> errorGenerator)
+  {
+    return FileApprover.registerErrorGenerator(errorGenerator);
+  }
 }
diff --git a/approvaltests/src/main/java/org/approvaltests/approvers/FileApprover.java b/approvaltests/src/main/java/org/approvaltests/approvers/FileApprover.java
index c7ed23fe8..fefcab66a 100644
--- a/approvaltests/src/main/java/org/approvaltests/approvers/FileApprover.java
+++ b/approvaltests/src/main/java/org/approvaltests/approvers/FileApprover.java
@@ -15,22 +15,35 @@
 
 public class FileApprover implements ApprovalApprover
 {
-  private File                                received;
-  private File                                approved;
-  private final ApprovalWriter                writer;
-  private Function2<File, File, VerifyResult> approver;
-  public static final ApprovalTracker         tracker = new ApprovalTracker();
+  public static final ApprovalTracker             tracker        = new ApprovalTracker();
+  private static Function2<String, String, Error> errorGenerator = FileApprover::createError;
+  private File                                    received;
+  private File                                    approved;
+  private final ApprovalWriter                    writer;
+  private Function2<File, File, VerifyResult>     approver;
   public FileApprover(ApprovalWriter writer, ApprovalNamer namer)
   {
     this(writer, namer, FileApprover::approveTextFile);
   }
   public FileApprover(ApprovalWriter writer, ApprovalNamer namer, Function2<File, File, VerifyResult> approver)
   {
+    this(namer.getReceivedFile(writer.getFileExtensionWithDot()),
+        namer.getApprovedFile(writer.getFileExtensionWithDot()), writer, approver);
+  }
+  public FileApprover(File received, File approved, ApprovalWriter writer,
+      Function2<File, File, VerifyResult> approver)
+  {
+    this.received = received;
+    this.approved = approved;
     this.writer = writer;
-    received = namer.getReceivedFile(writer.getFileExtensionWithDot());
-    approved = namer.getApprovedFile(writer.getFileExtensionWithDot());
     this.approver = approver;
   }
+  public static AutoCloseable registerErrorGenerator(Function2<String, String, Error> errorGenerator)
+  {
+    Function2<String, String, Error> old = FileApprover.errorGenerator;
+    FileApprover.errorGenerator = errorGenerator;
+    return () -> FileApprover.errorGenerator = old;
+  }
   public VerifyResult approve()
   {
     tracker.assertUnique(approved.getAbsolutePath());
@@ -58,7 +71,7 @@ public VerifyResult reportFailure(ApprovalFailureReporter reporter)
   }
   public void fail()
   {
-    throw createError(received.getAbsolutePath(), approved.getAbsolutePath());
+    throw errorGenerator.call(received.getAbsolutePath(), approved.getAbsolutePath());
   }
   private static Error createError(String received, String approved)
   {