LibDiff: Make Diff::from_text fallible

Userland/Libraries/LibCpp/SemanticSyntaxHighlighter.cpp

@@ -55,7 +55,7 @@ void SemanticSyntaxHighlighter::rehighlight(Palette const& palette)
 
         // FIXME: Computing the diff on the entire document's tokens is quite inefficient.
         //        An improvement over this could be only including the tokens that are in edited text ranges in the diff.
-        auto diff_hunks = Diff::from_text(previous.view(), current.view());
+        auto diff_hunks = Diff::from_text(previous.view(), current.view()).release_value_but_fixme_should_propagate_errors();
         for (auto& token : current_tokens) {
             new_tokens_info.append(CodeComprehension::TokenInfo { CodeComprehension::TokenInfo::SemanticType::Unknown,
                 token.start().line, token.start().column, token.end().line, token.end().column });

Userland/Libraries/LibDiff/Generator.cpp

@@ -8,7 +8,7 @@
 
 namespace Diff {
 
-Vector<Hunk> from_text(StringView old_text, StringView new_text)
+ErrorOr<Vector<Hunk>> from_text(StringView old_text, StringView new_text)
 {
     auto old_lines = old_text.lines();
     auto new_lines = new_text.lines();
@@ -33,7 +33,7 @@ Vector<Hunk> from_text(StringView old_text, StringView new_text)
     };
 
     auto dp_matrix = Vector<Cell>();
-    dp_matrix.resize((old_lines.size() + 1) * (new_lines.size() + 1));
+    TRY(dp_matrix.try_resize((old_lines.size() + 1) * (new_lines.size() + 1)));
 
     auto dp = [&dp_matrix, width = old_lines.size() + 1](size_t i, size_t j) -> Cell& {
         return dp_matrix[i + width * j];
@@ -66,27 +66,31 @@ Vector<Hunk> from_text(StringView old_text, StringView new_text)
     Hunk cur_hunk;
     bool in_hunk = false;
 
-    auto update_hunk = [&](size_t i, size_t j, Direction direction) {
+    auto update_hunk = [&](size_t i, size_t j, Direction direction) -> ErrorOr<void> {
         if (!in_hunk) {
             in_hunk = true;
             cur_hunk = { i, j, {}, {} };
         }
         if (direction == Direction::Down) {
-            cur_hunk.added_lines.append(new_lines[j]);
+            TRY(cur_hunk.added_lines.try_append(new_lines[j]));
         } else if (direction == Direction::Right) {
-            cur_hunk.removed_lines.append(old_lines[i]);
+            TRY(cur_hunk.removed_lines.try_append(old_lines[i]));
         }
+
+        return {};
     };
 
-    auto flush_hunk = [&]() {
+    auto flush_hunk = [&]() -> ErrorOr<void> {
         if (in_hunk) {
             if (cur_hunk.added_lines.size() > 0)
                 cur_hunk.target_start_line++;
             if (cur_hunk.removed_lines.size() > 0)
                 cur_hunk.original_start_line++;
-            hunks.append(cur_hunk);
+            TRY(hunks.try_append(cur_hunk));
             in_hunk = false;
         }
+
+        return {};
     };
 
     size_t i = 0;
@@ -95,28 +99,28 @@ Vector<Hunk> from_text(StringView old_text, StringView new_text)
     while (i < old_lines.size() && j < new_lines.size()) {
         auto& cell = dp(i, j);
         if (cell.direction == Direction::Down) {
-            update_hunk(i, j, cell.direction);
+            TRY(update_hunk(i, j, cell.direction));
             ++j;
         } else if (cell.direction == Direction::Right) {
-            update_hunk(i, j, cell.direction);
+            TRY(update_hunk(i, j, cell.direction));
             ++i;
         } else {
             ++i;
             ++j;
-            flush_hunk();
+            TRY(flush_hunk());
         }
     }
 
     while (i < old_lines.size()) {
-        update_hunk(i, new_lines.is_empty() ? 0 : new_lines.size() - 1, Direction::Right); // Remove a line
+        TRY(update_hunk(i, new_lines.is_empty() ? 0 : new_lines.size() - 1, Direction::Right)); // Remove a line
         ++i;
     }
     while (j < new_lines.size()) {
-        update_hunk(old_lines.is_empty() ? 0 : old_lines.size() - 1, j, Direction::Down); // Add a line
+        TRY(update_hunk(old_lines.is_empty() ? 0 : old_lines.size() - 1, j, Direction::Down)); // Add a line
         ++j;
     }
 
-    flush_hunk();
+    TRY(flush_hunk());
 
     return hunks;
 }

Userland/Libraries/LibDiff/Generator.h

@@ -7,9 +7,10 @@
 #pragma once
 
 #include "Hunks.h"
+#include <AK/Error.h>
 
 namespace Diff {
 
-Vector<Hunk> from_text(StringView old_text, StringView new_text);
+ErrorOr<Vector<Hunk>> from_text(StringView old_text, StringView new_text);
 
 }

Userland/Utilities/diff.cpp

@@ -31,7 +31,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
     auto const color_output = TRY(Core::System::isatty(STDOUT_FILENO)) ? Diff::ColorOutput::Yes : Diff::ColorOutput::No;
 
-    auto hunks = Diff::from_text(TRY(file1->read_until_eof()), TRY(file2->read_until_eof()));
+    auto hunks = TRY(Diff::from_text(TRY(file1->read_until_eof()), TRY(file2->read_until_eof())));
     for (auto const& hunk : hunks)
         TRY(Diff::write_normal(hunk, *out, color_output));
 

Userland/Utilities/headless-browser.cpp

@@ -254,7 +254,7 @@ static ErrorOr<TestResult> run_test(HeadlessWebContentView& view, StringView inp
     else
         outln("\nTest failed: {}", input_path);
 
-    auto hunks = Diff::from_text(expectation, actual);
+    auto hunks = TRY(Diff::from_text(expectation, actual));
     auto out = TRY(Core::File::standard_output());
     for (auto const& hunk : hunks) {
         TRY(out->write_formatted("Hunk: "));