From aaa6c2d98c9641ad6e6b477e33cbd04e67afbdbc Mon Sep 17 00:00:00 2001
From: NotSomeBot <43829743+mariusdkm@users.noreply.github.com>
Date: Sun, 16 Apr 2023 18:06:35 +0200
Subject: [PATCH 1/3] Fix: Error message

---
 dash/_validate.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dash/_validate.py b/dash/_validate.py
index d1b94a284f..20381dccfa 100644
--- a/dash/_validate.py
+++ b/dash/_validate.py
@@ -201,7 +201,7 @@ def validate_multi_return(outputs_list, output_value, callback_id):
                     dedent(
                         f"""
                         Invalid number of output values for {callback_id} item {i}.
-                        Expected {len(vi)}, got {len(outi)}
+                        Expected {len(outi)}, got {len(vi)}
                         output spec: {outi!r}
                         output value: {vi!r}
                         """

From 8e89bc3d1f48e6c819b4d534ab0fd6bd9427803d Mon Sep 17 00:00:00 2001
From: mariusdkm <mariusdkm@gmail.com>
Date: Thu, 20 Apr 2023 17:36:33 +0200
Subject: [PATCH 2/3] Chore: rename variables

---
 dash/_validate.py | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/dash/_validate.py b/dash/_validate.py
index 20381dccfa..5b1cdd0548 100644
--- a/dash/_validate.py
+++ b/dash/_validate.py
@@ -161,49 +161,49 @@ def validate_and_group_input_args(flat_args, arg_index_grouping):
     return func_args, func_kwargs
 
 
-def validate_multi_return(outputs_list, output_value, callback_id):
-    if not isinstance(output_value, (list, tuple)):
+def validate_multi_return(output_lists, output_values, callback_id):
+    if not isinstance(output_values, (list, tuple)):
         raise exceptions.InvalidCallbackReturnValue(
             dedent(
                 f"""
                 The callback {callback_id} is a multi-output.
                 Expected the output type to be a list or tuple but got:
-                {output_value!r}.
+                {output_values!r}.
                 """
             )
         )
 
-    if len(output_value) != len(outputs_list):
+    if len(output_values) != len(output_lists):
         raise exceptions.InvalidCallbackReturnValue(
             f"""
             Invalid number of output values for {callback_id}.
-            Expected {len(outputs_list)}, got {len(output_value)}
+            Expected {len(output_lists)}, got {len(output_values)}
             """
         )
 
-    for i, outi in enumerate(outputs_list):
-        if isinstance(outi, list):
-            vi = output_value[i]
-            if not isinstance(vi, (list, tuple)):
+    for i, output_spec in enumerate(output_lists):
+        if isinstance(output_spec, list):
+            output_value = output_values[i]
+            if not isinstance(output_value, (list, tuple)):
                 raise exceptions.InvalidCallbackReturnValue(
                     dedent(
                         f"""
                         The callback {callback_id} output {i} is a wildcard multi-output.
                         Expected the output type to be a list or tuple but got:
-                        {vi!r}.
-                        output spec: {outi!r}
+                        {output_value!r}.
+                        output spec: {output_spec!r}
                         """
                     )
                 )
 
-            if len(vi) != len(outi):
+            if len(output_value) != len(output_spec):
                 raise exceptions.InvalidCallbackReturnValue(
                     dedent(
                         f"""
                         Invalid number of output values for {callback_id} item {i}.
-                        Expected {len(outi)}, got {len(vi)}
-                        output spec: {outi!r}
-                        output value: {vi!r}
+                        Expected {len(output_spec)}, got {len(output_value)}
+                        output spec: {output_spec!r}
+                        output value: {output_value!r}
                         """
                     )
                 )

From 555e60fac9a973a207813ae15b4891c927b51af1 Mon Sep 17 00:00:00 2001
From: mariusdkm <mariusdkm@gmail.com>
Date: Thu, 20 Apr 2023 17:37:57 +0200
Subject: [PATCH 3/3] Add: changelog entry

---
 CHANGELOG.md | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8955cef5a8..4600b8a068 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,12 @@
 All notable changes to `dash` will be documented in this file.
 This project adheres to [Semantic Versioning](https://semver.org/).
 
+## [UNRELEASED]
+
+## Fixed
+
+- [#2508](https://github.com/plotly/dash/pull/2508) Fix error message, when callback output has different length than spec
+
 ## [2.9.3] - 2023-04-13
 
 ## Fixed