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 prisma/prisma#14895

psl/psl-core/src/reformat.rs

@@ -137,7 +137,7 @@ fn push_missing_relation_attribute(inline_relation: walkers::InlineRelationWalke
         content.push(')');
 
         ctx.missing_bits.push(MissingBit {
-            position: before_newline(forward.ast_field().span().end, ctx.original_schema),
+            position: after_type(forward.ast_field().field_type.span().end, ctx.original_schema),
             content,
         })
     }
@@ -328,12 +328,10 @@ fn references_argument(inline: walkers::InlineRelationWalker<'_>) -> String {
     format!("references: [{}]", field_names.join(", "))
 }
 
-/// Assuming the last characters before span_end are newlines. We can fix this more thoroughly by
-/// 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");
-    match &original_schema[span_end - 2..span_end - 1] {
-        "\r" => span_end - 2,
-        _ => span_end - 1,
-    }
+fn after_type(type_span_end: usize, original_schema: &str) -> usize {
+    original_schema[type_span_end..]
+        .chars()
+        .position(|chr| !['[', ']', '?', '!'].contains(&chr))
+        .map(|pos| type_span_end + pos)
+        .unwrap_or(type_span_end)
 }

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.");
     }
 }

psl/psl/tests/reformatter/regression_add_relation_attribute_on_field_with_multi_byte_trailing_comment.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[]
+}

psl/psl/tests/reformatter/regression_add_relation_attribute_on_field_with_multi_byte_trailing_comment.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 @relation(fields: [], references: []) // 囧
+
+  id Int @id
+}
+
+model frownyface {
+  somes somemodel[]
+}