From cb87bb6e7f1147c7c63fc0d37c580681db3ebee8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=20Houl=C3=A9?= <tom@tomhoule.com>
Date: Wed, 30 Nov 2022 13:24:14 +0100
Subject: [PATCH] psl: fix newline boundary search in relation reformatting

When adding an @relation attribute to a forward relation field in the
relation reformatting code that deals with adding missing relation
fields and attributes, we searched for the last character before a
newline to check whether it is a carriage return, but we failed to
check whether the byte offset was a char boundary first. This caused
crashes.

closes https://github.com/prisma/prisma/issues/14895
---
 psl/psl-core/src/reformat.rs                  |  5 ++++
 psl/psl/tests/reformat_tests.rs               |  2 ++
 .../regression_thai_trailing_comments.prisma  | 23 +++++++++++++++++++
 ..._thai_trailing_comments.reformatted.prisma | 23 +++++++++++++++++++
 4 files changed, 53 insertions(+)
 create mode 100644 psl/psl/tests/reformatter/regression_thai_trailing_comments.prisma
 create mode 100644 psl/psl/tests/reformatter/regression_thai_trailing_comments.reformatted.prisma

diff --git a/psl/psl-core/src/reformat.rs b/psl/psl-core/src/reformat.rs
index d2ce95518505..b3334f7d7f66 100644
--- a/psl/psl-core/src/reformat.rs
+++ b/psl/psl-core/src/reformat.rs
@@ -332,6 +332,11 @@ fn references_argument(inline: walkers::InlineRelationWalker<'_>) -> String {
 /// not including the newline in field spans.
 fn before_newline(span_end: usize, original_schema: &str) -> usize {
     assert!(&original_schema[span_end - 1..span_end] == "\n");
+
+    if !original_schema.is_char_boundary(span_end - 2) {
+        return span_end - 1;
+    }
+
     match &original_schema[span_end - 2..span_end - 1] {
         "\r" => span_end - 2,
         _ => span_end - 1,
diff --git a/psl/psl/tests/reformat_tests.rs b/psl/psl/tests/reformat_tests.rs
index 1d070107a7d5..ea6207894047 100644
--- a/psl/psl/tests/reformat_tests.rs
+++ b/psl/psl/tests/reformat_tests.rs
@@ -28,6 +28,8 @@ fn run_reformat_test(test_file_path: &str) {
     }
 
     if reformat(&reformatted_text) != reformatted_text {
+        println!("=== reformatted ===\n{reformatted_text}");
+        println!("=== reformatted again ===\n{}", reformat(&reformatted_text));
         panic!("Reformatting this schema is not idempotent.");
     }
 }
diff --git a/psl/psl/tests/reformatter/regression_thai_trailing_comments.prisma b/psl/psl/tests/reformatter/regression_thai_trailing_comments.prisma
new file mode 100644
index 000000000000..faa11066ff2a
--- /dev/null
+++ b/psl/psl/tests/reformatter/regression_thai_trailing_comments.prisma
@@ -0,0 +1,23 @@
+// This is your Prisma schema file,
+// learn more about it in the docs: https://pris.ly/d/prisma-schema
+
+generator client {
+  provider = "prisma-client-js"
+  output   = "./generated/client"
+}
+
+datasource db {
+  provider = "sqlserver"
+  url = "***"
+}
+
+model somemodel {
+    frownyFaceId  String  
+    frownyFace frownyface // 囧
+
+    id Int @id
+}
+
+model frownyface {
+    somes somemodel[]
+}
diff --git a/psl/psl/tests/reformatter/regression_thai_trailing_comments.reformatted.prisma b/psl/psl/tests/reformatter/regression_thai_trailing_comments.reformatted.prisma
new file mode 100644
index 000000000000..5a3ded258e9e
--- /dev/null
+++ b/psl/psl/tests/reformatter/regression_thai_trailing_comments.reformatted.prisma
@@ -0,0 +1,23 @@
+// This is your Prisma schema file,
+// learn more about it in the docs: https://pris.ly/d/prisma-schema
+
+generator client {
+  provider = "prisma-client-js"
+  output   = "./generated/client"
+}
+
+datasource db {
+  provider = "sqlserver"
+  url      = "***"
+}
+
+model somemodel {
+  frownyFaceId String
+  frownyFace   frownyface // 囧 @relation(fields: [], references: [])
+
+  id Int @id
+}
+
+model frownyface {
+  somes somemodel[]
+}