Avoid functions stabilised in Rust v1.91.0

The Flatpak build environment used by LOOT provides an older version of the Rust toolchain.

src/database/mod.rs

@@ -312,7 +312,10 @@ impl Database {
 }
 
 fn validate_write_path(output_path: &Path, mode: WriteMode) -> Result<(), WriteMetadataError> {
-    if !output_path.parent().is_some_and(|p| p == "" || p.exists()) {
+    if !output_path
+        .parent()
+        .is_some_and(|p| p.as_os_str().is_empty() || p.exists())
+    {
         Err(WriteMetadataError::new(
             output_path.into(),
             WriteMetadataErrorReason::ParentDirectoryNotFound,

src/metadata/error.rs

@@ -161,9 +161,17 @@ struct Position {
 
 fn adjust_location(pos: &Position, diff_span: &PreludeDiffSpan) -> (Position, bool) {
     if pos.line > diff_span.end_line {
+        // TODO: usize::saturating_sub_signed() is stable as of Rust 1.91.0, but the org.freedesktop.Sdk.Extension.rust-stable extension for LOOT's Flatpak build environment supplies an older version of Rust, so this can only be updated to use saturating_sub_signed() once it's available in that environment.
+        let line = if diff_span.lines_added_count.is_negative() {
+            pos.line
+                .saturating_add(diff_span.lines_added_count.unsigned_abs())
+        } else {
+            pos.line
+                .saturating_sub(diff_span.lines_added_count.unsigned_abs())
+        };
         (
             Position {
-                line: pos.line.saturating_sub_signed(diff_span.line_count_delta),
+                line,
                 column: pos.column,
             },
             false,

src/metadata/metadata_document.rs

@@ -392,24 +392,29 @@ fn replace_prelude(
         // The last line of the prelude.
         let prelude_end_line = prelude_start_line + new_prelude_line_count.saturating_sub(1);
 
-        let line_count_delta = new_prelude_line_count
-            .checked_signed_diff(old_prelude_line_count)
-            .ok_or_else(|| {
-                ParseMetadataError::new(
-                    saphyr::Marker::new(before_prelude.len(), prelude_start_line, 0),
-                    MetadataParsingErrorReason::PreludeSubstitutionOverflow {
-                        new_prelude_count: new_prelude_line_count,
-                        old_prelude_count: old_prelude_line_count,
-                    },
-                )
-            })?;
+        // TODO: usize::checked_signed_diff() is stable as of Rust 1.91.0, but the org.freedesktop.Sdk.Extension.rust-stable extension for LOOT's Flatpak build environment supplies an older version of Rust, so this can only be updated to use checked_signed_diff() once it's available in that environment.
+        let lines_added_count = if new_prelude_line_count >= old_prelude_line_count {
+            isize::try_from(new_prelude_line_count - old_prelude_line_count)
+        } else {
+            isize::try_from(old_prelude_line_count - new_prelude_line_count).map(std::ops::Neg::neg)
+        };
+
+        let lines_added_count = lines_added_count.map_err(|_e| {
+            ParseMetadataError::new(
+                saphyr::Marker::new(before_prelude.len(), prelude_start_line, 0),
+                MetadataParsingErrorReason::PreludeSubstitutionOverflow {
+                    new_prelude_count: new_prelude_line_count,
+                    old_prelude_count: old_prelude_line_count,
+                },
+            )
+        })?;
 
         Ok(MasterlistWithReplacedPrelude {
             masterlist,
             meta: Some(PreludeDiffSpan {
                 start_line: prelude_start_line,
                 end_line: prelude_end_line,
-                line_count_delta,
+                lines_added_count,
             }),
         })
     } else {
@@ -1154,7 +1159,7 @@ plugins:
             assert_eq!(expected_result, result.masterlist);
             assert_eq!(2, result.meta.as_ref().unwrap().start_line);
             assert_eq!(5, result.meta.as_ref().unwrap().end_line);
-            assert_eq!(2, result.meta.as_ref().unwrap().line_count_delta);
+            assert_eq!(2, result.meta.as_ref().unwrap().lines_added_count);
         }
 
         #[test]
@@ -1183,7 +1188,7 @@ plugins:
             assert_eq!(expected_result, result.masterlist);
             assert_eq!(2, result.meta.as_ref().unwrap().start_line);
             assert_eq!(5, result.meta.as_ref().unwrap().end_line);
-            assert_eq!(3, result.meta.as_ref().unwrap().line_count_delta);
+            assert_eq!(3, result.meta.as_ref().unwrap().lines_added_count);
         }
 
         #[test]
@@ -1211,7 +1216,7 @@ plugins:
             assert_eq!(expected_result, result.masterlist);
             assert_eq!(2, result.meta.as_ref().unwrap().start_line);
             assert_eq!(4, result.meta.as_ref().unwrap().end_line);
-            assert_eq!(1, result.meta.as_ref().unwrap().line_count_delta);
+            assert_eq!(1, result.meta.as_ref().unwrap().lines_added_count);
         }
 
         #[test]
@@ -1238,7 +1243,7 @@ plugins:
             assert_eq!(expected_result, result.masterlist);
             assert_eq!(2, result.meta.as_ref().unwrap().start_line);
             assert_eq!(4, result.meta.as_ref().unwrap().end_line);
-            assert_eq!(2, result.meta.as_ref().unwrap().line_count_delta);
+            assert_eq!(2, result.meta.as_ref().unwrap().lines_added_count);
         }
 
         #[test]
@@ -1267,7 +1272,7 @@ prelude:
             assert_eq!(expected_result, result.masterlist);
             assert_eq!(4, result.meta.as_ref().unwrap().start_line);
             assert_eq!(7, result.meta.as_ref().unwrap().end_line);
-            assert_eq!(1, result.meta.as_ref().unwrap().line_count_delta);
+            assert_eq!(1, result.meta.as_ref().unwrap().lines_added_count);
         }
 
         #[test]
@@ -1308,7 +1313,7 @@ plugins:
             assert_eq!(expected_result, result.masterlist);
             assert_eq!(5, result.meta.as_ref().unwrap().start_line);
             assert_eq!(11, result.meta.as_ref().unwrap().end_line);
-            assert_eq!(6, result.meta.as_ref().unwrap().line_count_delta);
+            assert_eq!(6, result.meta.as_ref().unwrap().lines_added_count);
         }
 
         #[test]
@@ -1338,7 +1343,7 @@ plugins:
             assert_eq!(expected_result, result.masterlist);
             assert_eq!(2, result.meta.as_ref().unwrap().start_line);
             assert_eq!(5, result.meta.as_ref().unwrap().end_line);
-            assert_eq!(2, result.meta.as_ref().unwrap().line_count_delta);
+            assert_eq!(2, result.meta.as_ref().unwrap().lines_added_count);
         }
 
         #[test]
@@ -1362,7 +1367,7 @@ plugins:
             assert_eq!(expected_result, result.masterlist);
             assert_eq!(2, result.meta.as_ref().unwrap().start_line);
             assert_eq!(2, result.meta.as_ref().unwrap().end_line);
-            assert_eq!(-1, result.meta.as_ref().unwrap().line_count_delta);
+            assert_eq!(-1, result.meta.as_ref().unwrap().lines_added_count);
         }
 
         #[test]
@@ -1394,7 +1399,7 @@ plugins:
             assert_eq!(expected_result, result.masterlist);
             assert_eq!(2, result.meta.as_ref().unwrap().start_line);
             assert_eq!(5, result.meta.as_ref().unwrap().end_line);
-            assert_eq!(0, result.meta.as_ref().unwrap().line_count_delta);
+            assert_eq!(0, result.meta.as_ref().unwrap().lines_added_count);
         }
 
         #[test]
@@ -1425,7 +1430,7 @@ plugins:
             assert_eq!(expected_result, result.masterlist);
             assert_eq!(2, result.meta.as_ref().unwrap().start_line);
             assert_eq!(5, result.meta.as_ref().unwrap().end_line);
-            assert_eq!(1, result.meta.as_ref().unwrap().line_count_delta);
+            assert_eq!(1, result.meta.as_ref().unwrap().lines_added_count);
         }
     }
 }

src/metadata/mod.rs

@@ -22,7 +22,7 @@ pub use tag::{Tag, TagSuggestion};
 struct PreludeDiffSpan {
     start_line: usize,
     end_line: usize,
-    line_count_delta: isize,
+    lines_added_count: isize,
 }
 
 #[cfg(test)]