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LibDiff: Add support for generating diffs with surrounding context

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While not used in normal diffs due to limitations in the format, this
may be used in context and unified format diffs.
This commit is contained in:
Shannon Booth 2023-06-27 21:28:48 +12:00 • committed by Andrew Kaster
parent f528aedc85
commit 55a3dfec10
2 changed files with 66 additions and 38 deletions
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102
Userland/Libraries/LibDiff/Generator.cpp
View file

@ -9,7 +9,7 @@
namespace Diff {
ErrorOr<Vector<Hunk>> from_text(StringView old_text, StringView new_text)
ErrorOr<Vector<Hunk>> from_text(StringView old_text, StringView new_text, size_t context)
{
auto old_lines = old_text.lines();
auto new_lines = new_text.lines();
@ -65,39 +65,16 @@ ErrorOr<Vector<Hunk>> from_text(StringView old_text, StringView new_text)
Vector<Hunk> hunks;
Hunk cur_hunk;
bool in_hunk = false;
auto update_hunk = [&](size_t i, size_t j, Direction direction) -> ErrorOr<void> {
if (!in_hunk) {
HunkLocation location;
location.old_range.start_line = i;
location.new_range.start_line = j;
in_hunk = true;
cur_hunk = { location, {} };
}
if (direction == Direction::Down) {
TRY(cur_hunk.lines.try_append(Line { Line::Operation::Addition, TRY(String::from_utf8(new_lines[j])) }));
cur_hunk.location.new_range.number_of_lines++;
} else if (direction == Direction::Right) {
TRY(cur_hunk.lines.try_append(Line { Line::Operation::Removal, TRY(String::from_utf8(old_lines[i])) }));
cur_hunk.location.old_range.number_of_lines++;
}
return {};
};
auto flush_hunk = [&]() -> ErrorOr<void> {
if (in_hunk) {
// A file with no content has a zero indexed start line.
if (cur_hunk.location.new_range.start_line != 0 || cur_hunk.location.new_range.number_of_lines != 0)
cur_hunk.location.new_range.start_line++;
if (cur_hunk.location.old_range.start_line != 0 || cur_hunk.location.old_range.number_of_lines != 0)
cur_hunk.location.old_range.start_line++;
// A file with no content has a zero indexed start line.
if (cur_hunk.location.new_range.start_line != 0 || cur_hunk.location.new_range.number_of_lines != 0)
cur_hunk.location.new_range.start_line++;
if (cur_hunk.location.old_range.start_line != 0 || cur_hunk.location.old_range.number_of_lines != 0)
cur_hunk.location.old_range.start_line++;
TRY(hunks.try_append(cur_hunk));
in_hunk = false;
}
TRY(hunks.try_append(cur_hunk));
cur_hunk.lines.clear();
return {};
};
@ -105,31 +82,82 @@ ErrorOr<Vector<Hunk>> from_text(StringView old_text, StringView new_text)
size_t i = 0;
size_t j = 0;
auto set_up_hunk_prepended_with_context = [&](Hunk& hunk) -> ErrorOr<void> {
// Prefix the hunk with requested number context lines, and set the hunk location to where that context begins.
size_t available_context = min(i, context);
hunk.location.old_range = { i - available_context, available_context };
hunk.location.new_range = { j - available_context, available_context };
for (size_t offset = 0; offset < available_context; ++offset) {
size_t context_line = i + offset - available_context;
TRY(hunk.lines.try_append(Line { Line::Operation::Context, TRY(String::from_utf8(new_lines[context_line])) }));
}
return {};
};
size_t current_context = 0;
while (i < old_lines.size() && j < new_lines.size()) {
auto& cell = dp(i, j);
if (cell.direction == Direction::Down) {
TRY(update_hunk(i, j, cell.direction));
if (cur_hunk.lines.is_empty())
TRY(set_up_hunk_prepended_with_context(cur_hunk));
TRY(cur_hunk.lines.try_append(Line { Line::Operation::Addition, TRY(String::from_utf8(new_lines[j])) }));
cur_hunk.location.new_range.number_of_lines++;
++j;
current_context = 0;
} else if (cell.direction == Direction::Right) {
TRY(update_hunk(i, j, cell.direction));
if (cur_hunk.lines.is_empty())
TRY(set_up_hunk_prepended_with_context(cur_hunk));
TRY(cur_hunk.lines.try_append(Line { Line::Operation::Removal, TRY(String::from_utf8(old_lines[i])) }));
cur_hunk.location.old_range.number_of_lines++;
++i;
current_context = 0;
} else {
if (!cur_hunk.lines.is_empty()) {
// We're currently in the middle of generating a hunk and have found a context line. If we have already added
// the number of context lines that were requested then we have already finished with this hunk. Otherwise we
// need to continue looking through the hunk until we have located the requested number of context lines in a
// row.
if (current_context == context) {
TRY(flush_hunk());
} else {
TRY(cur_hunk.lines.try_append(Line { Line::Operation::Context, TRY(String::from_utf8(old_lines[i])) }));
cur_hunk.location.new_range.number_of_lines++;
cur_hunk.location.old_range.number_of_lines++;
}
++current_context;
}
++i;
++j;
TRY(flush_hunk());
}
}
while (i < old_lines.size()) {
TRY(update_hunk(i, new_lines.is_empty() ? 0 : new_lines.size() - 1, Direction::Right)); // Remove a line
if (cur_hunk.lines.is_empty())
TRY(set_up_hunk_prepended_with_context(cur_hunk));
TRY(cur_hunk.lines.try_append(Line { Line::Operation::Removal, TRY(String::from_utf8(old_lines[i])) }));
cur_hunk.location.old_range.number_of_lines++;
++i;
}
while (j < new_lines.size()) {
TRY(update_hunk(old_lines.is_empty() ? 0 : old_lines.size() - 1, j, Direction::Down)); // Add a line
if (cur_hunk.lines.is_empty())
TRY(set_up_hunk_prepended_with_context(cur_hunk));
TRY(cur_hunk.lines.try_append(Line { Line::Operation::Addition, TRY(String::from_utf8(new_lines[j])) }));
cur_hunk.location.new_range.number_of_lines++;
++j;
}
TRY(flush_hunk());
if (!cur_hunk.lines.is_empty())
TRY(flush_hunk());
return hunks;
}