From 3144d0e6c9119fde14661fd4c8b1638ed435f14c Mon Sep 17 00:00:00 2001
From: Hannes Hayashi <hannes.h@doit.com>
Date: Wed, 3 Jun 2026 11:38:54 +0200
Subject: [PATCH] fix: preserve leading underscores in ToPascalCase to avoid
 field collisions
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Properties like _id and id both normalized to Id in PascalCase,
causing Go struct field redeclaration errors. Now _id produces
UnderscoreId while id remains Id.

This is a targeted fix — only identifiers starting with underscore
are affected. The tfsdk tags still use the original attribute name.
---
 internal/schema/framework_identifier.go      | 12 +++++++++++-
 internal/schema/framework_identifier_test.go |  8 ++++----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/internal/schema/framework_identifier.go b/internal/schema/framework_identifier.go
index 51a3837b..d9858e49 100644
--- a/internal/schema/framework_identifier.go
+++ b/internal/schema/framework_identifier.go
@@ -78,10 +78,20 @@ func (identifier FrameworkIdentifier) ToPrefixCamelCase(prefix string) string {
 // ToPascalCase will return a pascal case formatted string of the identifier.
 // Example:
 //   - example_resource_thing -> ExampleResourceThing
+//   - _id -> UnderscoreId
 func (identifier FrameworkIdentifier) ToPascalCase() string {
-	return snakeLetters.ReplaceAllStringFunc(string(identifier), func(s string) string {
+	input := string(identifier)
+
+	result := snakeLetters.ReplaceAllStringFunc(input, func(s string) string {
 		return strings.ToUpper(strings.Replace(s, "_", "", -1))
 	})
+
+	// Preserve leading underscore to avoid collisions (e.g., _id vs id).
+	if strings.HasPrefix(input, "_") {
+		result = "Underscore" + result
+	}
+
+	return result
 }
 
 // ToPrefixPascalCase will return a pascal case formatted string of the identifier,
diff --git a/internal/schema/framework_identifier_test.go b/internal/schema/framework_identifier_test.go
index 43e97988..bb2fea03 100644
--- a/internal/schema/framework_identifier_test.go
+++ b/internal/schema/framework_identifier_test.go
@@ -79,7 +79,7 @@ func TestFrameworkIdentifier_ToCamelCase(t *testing.T) {
 		},
 		"leading underscore": {
 			identifier: "_thing",
-			want:       "thing",
+			want:       "underscoreThing",
 		},
 		"middle underscore": {
 			identifier: "fake_thing",
@@ -120,7 +120,7 @@ func TestFrameworkIdentifier_ToPrefixCamelCase(t *testing.T) {
 		},
 		"leading underscore": {
 			identifier: "_thing",
-			want:       "thing",
+			want:       "underscoreThing",
 		},
 		"middle underscore": {
 			identifier: "fake_thing",
@@ -193,7 +193,7 @@ func TestFrameworkIdentifier_ToPascalCase(t *testing.T) {
 		},
 		"leading underscore": {
 			identifier: "_thing",
-			want:       "Thing",
+			want:       "UnderscoreThing",
 		},
 		"middle underscore": {
 			identifier: "fake_thing",
@@ -234,7 +234,7 @@ func TestFrameworkIdentifier_ToPrefixPascalCase(t *testing.T) {
 		},
 		"leading underscore": {
 			identifier: "_thing",
-			want:       "Thing",
+			want:       "UnderscoreThing",
 		},
 		"middle underscore": {
 			identifier: "fake_thing",