Only set next/prev on potentially changed syntax nodes

Otherwise we end up running dijkstra on nodes at the end that we've
already marked as unchanged, and erroneously claim they're novel.

Fixes #112

CHANGELOG.md

@@ -4,6 +4,9 @@
 
 Improved performance when all file changes are close together.
 
+Fixed a bug where syntax after the last changed item was incorrectly
+marked as added.
+
 ### Display
 
 Added syntax highlighting for unchanged comments, strings and types.

src/dijkstra.rs

@@ -95,7 +95,7 @@ mod tests {
     use crate::{
         graph::Edge::*,
         positions::SingleLineSpan,
-        syntax::{init_info, AtomKind, ChangeKind},
+        syntax::{init_all_info, AtomKind, ChangeKind},
     };
 
     use itertools::Itertools;
@@ -124,7 +124,7 @@ mod tests {
         let lhs = Syntax::new_atom(&arena, pos_helper(0), "foo", AtomKind::Normal);
         // Same content as LHS.
         let rhs = Syntax::new_atom(&arena, pos_helper(0), "foo", AtomKind::Normal);
-        init_info(&[lhs], &[rhs]);
+        init_all_info(&[lhs], &[rhs]);
 
         let start = Vertex {
             lhs_syntax: Some(lhs),
@@ -167,7 +167,7 @@ mod tests {
             "]",
             pos_helper(2),
         )];
-        init_info(&lhs, &rhs);
+        init_all_info(&lhs, &rhs);
 
         let start = Vertex {
             lhs_syntax: lhs.get(0).copied(),
@@ -211,7 +211,7 @@ mod tests {
             "]",
             pos_helper(3),
         )];
-        init_info(&lhs, &rhs);
+        init_all_info(&lhs, &rhs);
 
         let start = Vertex {
             lhs_syntax: lhs.get(0).copied(),
@@ -259,7 +259,7 @@ mod tests {
             "}",
             pos_helper(4),
         )];
-        init_info(&lhs, &rhs);
+        init_all_info(&lhs, &rhs);
 
         let start = Vertex {
             lhs_syntax: lhs.get(0).copied(),
@@ -299,7 +299,7 @@ mod tests {
             "foo",
             AtomKind::Normal,
         )];
-        init_info(&lhs, &rhs);
+        init_all_info(&lhs, &rhs);
 
         let start = Vertex {
             lhs_syntax: lhs.get(0).copied(),
@@ -339,7 +339,7 @@ mod tests {
         )];
 
         let rhs = vec![];
-        init_info(&lhs, &rhs);
+        init_all_info(&lhs, &rhs);
 
         let start = Vertex {
             lhs_syntax: lhs.get(0).copied(),
@@ -379,7 +379,7 @@ mod tests {
         ];
 
         let rhs = vec![];
-        init_info(&lhs, &rhs);
+        init_all_info(&lhs, &rhs);
 
         let start = Vertex {
             lhs_syntax: lhs.get(0).copied(),
@@ -464,7 +464,7 @@ mod tests {
             "]",
             pos_helper(100),
         )];
-        init_info(&lhs, &rhs);
+        init_all_info(&lhs, &rhs);
 
         let start = Vertex {
             lhs_syntax: lhs.get(0).copied(),
@@ -503,7 +503,7 @@ mod tests {
             "the quick brown cat",
             AtomKind::Comment,
         )];
-        init_info(&lhs, &rhs);
+        init_all_info(&lhs, &rhs);
 
         let start = Vertex {
             lhs_syntax: lhs.get(0).copied(),
@@ -537,7 +537,7 @@ mod tests {
             "foo bar",
             AtomKind::Comment,
         )];
-        init_info(&lhs, &rhs);
+        init_all_info(&lhs, &rhs);
 
         let start = Vertex {
             lhs_syntax: lhs.get(0).copied(),
@@ -579,7 +579,7 @@ mod tests {
             "the quick brown fox.",
             AtomKind::Comment,
         )];
-        init_info(&lhs, &rhs);
+        init_all_info(&lhs, &rhs);
 
         let start = Vertex {
             lhs_syntax: lhs.get(0).copied(),
@@ -604,7 +604,7 @@ mod tests {
         let arena = Arena::new();
         let lhs = Syntax::new_atom(&arena, pos_helper(1), "foo", AtomKind::Normal);
         let rhs = Syntax::new_atom(&arena, pos_helper(1), "foo", AtomKind::Normal);
-        init_info(&[lhs], &[rhs]);
+        init_all_info(&[lhs], &[rhs]);
 
         mark_syntax(Some(lhs), Some(rhs));
         assert_eq!(lhs.change(), Some(ChangeKind::Unchanged(rhs)));
@@ -616,7 +616,7 @@ mod tests {
         let arena = Arena::new();
         let lhs = Syntax::new_atom(&arena, pos_helper(1), "foo", AtomKind::Normal);
         let rhs = Syntax::new_atom(&arena, pos_helper(1), "bar", AtomKind::Normal);
-        init_info(&[lhs], &[rhs]);
+        init_all_info(&[lhs], &[rhs]);
 
         mark_syntax(Some(lhs), Some(rhs));
         assert_eq!(lhs.change(), Some(ChangeKind::Novel));

src/main.rs

@@ -48,6 +48,7 @@ use clap::{crate_version, App, AppSettings, Arg};
 use sliders::fix_all_sliders;
 use std::{env, path::Path};
 use summary::DiffResult;
+use syntax::init_next_prev;
 use typed_arena::Arena;
 use unchanged::skip_unchanged_at_ends;
 use walkdir::WalkDir;
@@ -57,7 +58,7 @@ use crate::{
     files::{is_probably_binary, read_or_die},
     line_parser as lp,
     lines::MaxLine,
-    syntax::{change_positions, init_info},
+    syntax::{change_positions, init_all_info},
     tree_sitter_parser as tsp,
 };
 
@@ -221,7 +222,7 @@ fn main() {
                     let ts_lang = tsp::from_language(lang);
                     let arena = Arena::new();
                     let ast = tsp::parse(&arena, &src, &ts_lang);
-                    init_info(&ast, &[]);
+                    init_all_info(&ast, &[]);
                     println!("{:#?}", ast);
                 }
                 None => {
@@ -306,9 +307,12 @@ fn diff_file_content(display_path: &str, lhs_bytes: &[u8], rhs_bytes: &[u8]) ->
             let lhs = tsp::parse(&arena, &lhs_src, &ts_lang);
             let rhs = tsp::parse(&arena, &rhs_src, &ts_lang);
 
-            init_info(&lhs, &rhs);
+            init_all_info(&lhs, &rhs);
 
             let (possibly_changed_lhs, possibly_changed_rhs) = skip_unchanged_at_ends(&lhs, &rhs);
+            init_next_prev(&possibly_changed_lhs);
+            init_next_prev(&possibly_changed_rhs);
+
             mark_syntax(
                 possibly_changed_lhs.get(0).copied(),
                 possibly_changed_rhs.get(0).copied(),

src/sliders.rs

@@ -336,7 +336,7 @@ impl<'a> Syntax<'a> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::syntax::{init_info, AtomKind};
+    use crate::syntax::{init_all_info, AtomKind};
     use pretty_assertions::assert_eq;
     use typed_arena::Arena;
 
@@ -375,7 +375,7 @@ mod tests {
         }];
         let rhs = [Syntax::new_atom(&arena, pos, "a", AtomKind::Comment)];
 
-        init_info(&lhs, &rhs);
+        init_all_info(&lhs, &rhs);
 
         lhs[0].set_change(Unchanged(rhs[0]));
         lhs[1].set_change(Novel);
@@ -422,7 +422,7 @@ mod tests {
         }];
         let rhs = [Syntax::new_atom(&arena, pos, "a", AtomKind::Comment)];
 
-        init_info(&lhs, &rhs);
+        init_all_info(&lhs, &rhs);
 
         lhs[0].set_change(Novel);
         lhs[1].set_change(Novel);

src/syntax.rs

@@ -323,6 +323,12 @@ impl<'a> Syntax<'a> {
 }
 
 /// Initialise all the fields in `SyntaxInfo`.
+pub fn init_all_info<'a>(lhs_roots: &[&'a Syntax<'a>], rhs_roots: &[&'a Syntax<'a>]) {
+    init_info(lhs_roots, rhs_roots);
+    init_next_prev(lhs_roots);
+    init_next_prev(rhs_roots);
+}
+
 pub fn init_info<'a>(lhs_roots: &[&'a Syntax<'a>], rhs_roots: &[&'a Syntax<'a>]) {
     let mut id = 0;
     init_info_single(lhs_roots, &mut id);
@@ -392,12 +398,15 @@ fn set_content_id(nodes: &[&Syntax], existing: &mut HashMap<ContentKey, u32>) {
     }
 }
 
-fn init_info_single<'a>(roots: &[&'a Syntax<'a>], next_id: &mut u32) {
+pub fn init_next_prev<'a>(roots: &[&'a Syntax<'a>]) {
     set_next(roots, None);
     set_prev(roots, None);
+    set_prev_is_contiguous(roots);
+}
+
+fn init_info_single<'a>(roots: &[&'a Syntax<'a>], next_id: &mut u32) {
     set_parent(roots, None);
     set_num_ancestors(roots, 0);
-    set_prev_is_contiguous(roots);
     set_unique_id(roots, next_id)
 }
 
@@ -832,7 +841,7 @@ mod tests {
 
         let comment = Syntax::new_atom(&arena, pos.clone(), "foo", AtomKind::Comment);
         let atom = Syntax::new_atom(&arena, pos, "foo", AtomKind::Normal);
-        init_info(&[comment], &[atom]);
+        init_all_info(&[comment], &[atom]);
 
         assert_ne!(comment, atom);
     }
@@ -865,7 +874,7 @@ mod tests {
 
         let x = Syntax::new_atom(&arena, pos.clone(), "foo\nbar", AtomKind::Comment);
         let y = Syntax::new_atom(&arena, pos, "foo\n    bar", AtomKind::Comment);
-        init_info(&[x], &[y]);
+        init_all_info(&[x], &[y]);
 
         assert_eq!(x, y);
     }
@@ -899,7 +908,7 @@ mod tests {
             content: "foo".into(),
             kind: AtomKind::Normal,
         };
-        init_info(&[&lhs], &[&rhs]);
+        init_all_info(&[&lhs], &[&rhs]);
 
         assert_eq!(lhs, rhs);
     }

src/unchanged.rs

@@ -52,7 +52,7 @@ mod tests {
     use super::*;
     use crate::{
         guess_language,
-        syntax::init_info,
+        syntax::init_all_info,
         tree_sitter_parser::{from_language, parse},
     };
     use typed_arena::Arena;
@@ -64,7 +64,7 @@ mod tests {
 
         let lhs_nodes = parse(&arena, "unchanged A B", &config);
         let rhs_nodes = parse(&arena, "unchanged X", &config);
-        init_info(&lhs_nodes, &rhs_nodes);
+        init_all_info(&lhs_nodes, &rhs_nodes);
 
         let (lhs_after_skip, rhs_after_skip) = skip_unchanged_at_ends(&lhs_nodes, &rhs_nodes);
 
@@ -88,7 +88,7 @@ mod tests {
 
         let lhs_nodes = parse(&arena, "A B unchanged", &config);
         let rhs_nodes = parse(&arena, "X unchanged", &config);
-        init_info(&lhs_nodes, &rhs_nodes);
+        init_all_info(&lhs_nodes, &rhs_nodes);
 
         let (lhs_after_skip, rhs_after_skip) = skip_unchanged_at_ends(&lhs_nodes, &rhs_nodes);