psl: fix newline boundary search in relation reformatting (#3457)

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.

This commit fixes the problem by adding the relation attribute directly after the field type, rather than walking back from the end of the field (including trailing comment). We could do better with a proper AST.

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[]
+}