From c38fe7861c03a721adee673f72de20c12f9c14d8 Mon Sep 17 00:00:00 2001
From: Jannis Mattheis <contact@jmattheis.de>
Date: Sun, 31 Mar 2024 12:07:54 +0200
Subject: [PATCH] fix: error when enum and useUnderlyingTypeMethods conflict

---
 builder/enum.go                      |  4 +++
 builder/underlying.go                | 11 +++++++++
 docs/changelog.md                    |  6 +++++
 scenario/enum_underlying_conflict.md | 37 ++++++++++++++++++++++++++++
 4 files changed, 58 insertions(+)
 create mode 100644 scenario/enum_underlying_conflict.md

diff --git a/builder/enum.go b/builder/enum.go
index 02feb734..b291910f 100644
--- a/builder/enum.go
+++ b/builder/enum.go
@@ -14,6 +14,10 @@ type Enum struct{}
 
 // Matches returns true, if the builder can create handle the given types.
 func (*Enum) Matches(ctx *MethodContext, source, target *xtype.Type) bool {
+	return isEnum(ctx, source, target)
+}
+
+func isEnum(ctx *MethodContext, source, target *xtype.Type) bool {
 	return ctx.Conf.Enum.Enabled &&
 		source.Enum(&ctx.Conf.Enum).OK &&
 		target.Enum(&ctx.Conf.Enum).OK
diff --git a/builder/underlying.go b/builder/underlying.go
index 49e33b5c..c02e192c 100644
--- a/builder/underlying.go
+++ b/builder/underlying.go
@@ -1,6 +1,8 @@
 package builder
 
 import (
+	"fmt"
+
 	"github.com/dave/jennifer/jen"
 	"github.com/jmattheis/goverter/xtype"
 )
@@ -20,6 +22,15 @@ func (*UseUnderlyingTypeMethods) Matches(ctx *MethodContext, source, target *xty
 
 // Build creates conversion source code for the given source and target type.
 func (*UseUnderlyingTypeMethods) Build(gen Generator, ctx *MethodContext, sourceID *xtype.JenID, source, target *xtype.Type, errPath ErrorPath) ([]jen.Code, *xtype.JenID, *Error) {
+	if isEnum(ctx, source, target) {
+		return nil, nil, NewError(fmt.Sprintf(`The conversion between the types
+    %s
+    %s
+
+does qualify for enum conversion but also match an extend method via useUnderlyingTypeMethods.
+You have to disable enum or useUnderlyingTypeMethods to resolve the setting conflict.`, source.String, target.String))
+	}
+
 	sourceUnderlying, targetUnderlying := findUnderlyingExtendMapping(ctx, source, target)
 
 	innerSource := source
diff --git a/docs/changelog.md b/docs/changelog.md
index 625cc35f..e6dee378 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -4,6 +4,12 @@ import GH from './GH.vue';
 
 # Changelog
 
+## unreleased
+
+- Error when the settings [`enum`](reference/enum.md) and
+  [`useUnderlyingTypeMethods`](reference/useUnderlyingTypeMethods.md) conflict.
+  <GH issue="141" pr="142"/>
+
 ## v1.4.0
 
 - Add [Enum Support](guide/enum.md) <GH issue="61" pr="136"/>. Can be disabled
diff --git a/scenario/enum_underlying_conflict.md b/scenario/enum_underlying_conflict.md
new file mode 100644
index 00000000..57a11c6c
--- /dev/null
+++ b/scenario/enum_underlying_conflict.md
@@ -0,0 +1,37 @@
+input:
+    input.go: |
+        package example
+
+        // goverter:converter
+        // goverter:extend ConvertUnderlying
+        type Converter interface {
+            // goverter:useUnderlyingTypeMethods
+            Convert(SqlColor) Color
+        }
+
+        func ConvertUnderlying(s string) string {
+            return ""
+        }
+
+        type SqlColor string
+        const SqlColorDefault SqlColor = "default"
+
+        type Color string
+        const ColorDefault Color = "default"
+error: |-
+    Error while creating converter method:
+        func (github.com/jmattheis/goverter/execution.Converter).Convert(github.com/jmattheis/goverter/execution.SqlColor) github.com/jmattheis/goverter/execution.Color
+
+    | github.com/jmattheis/goverter/execution.SqlColor
+    |
+    source
+    target
+    |
+    | github.com/jmattheis/goverter/execution.Color
+
+    The conversion between the types
+        github.com/jmattheis/goverter/execution.SqlColor
+        github.com/jmattheis/goverter/execution.Color
+
+    does qualify for enum conversion but also match an extend method via useUnderlyingTypeMethods.
+    You have to disable enum or useUnderlyingTypeMethods to resolve the setting conflict.