reconcile/examples/compare-with-diff-match-patch.rs

95 lines
3.2 KiB
Rust

use std::panic;
use diff_match_patch_rs::{Compat, DiffMatchPatch, PatchInput};
use reconcile_text::{BuiltinTokenizer, reconcile};
fn dmp_merge(parent: &str, left: &str, right: &str) -> Option<String> {
let parent = parent.to_owned();
let left = left.to_owned();
let right = right.to_owned();
// diff-match-patch-rs can panic on some inputs, so we catch that.
panic::catch_unwind(|| {
let dmp = DiffMatchPatch::new();
let diffs = dmp.diff_main::<Compat>(&parent, &left).ok()?;
let patches = dmp
.patch_make(PatchInput::new_text_diffs(&parent, &diffs))
.ok()?;
let (result, _) = dmp.patch_apply(&patches, &right).ok()?;
Some(result)
})
.ok()
.flatten()
}
fn try_merge(parent: &str, left: &str, right: &str) {
let dmp_result = dmp_merge(parent, left, right);
let reconcile_result = reconcile(
parent,
&left.into(),
&right.into(),
&*BuiltinTokenizer::Word,
)
.apply()
.text();
println!("Parent: {parent:?}");
println!("Left: {left:?}");
println!("Right: {right:?}");
println!();
match dmp_result {
Some(r) => println!("diff-match-patch: {r:?}"),
None => println!("diff-match-patch: <panic or error>"),
}
println!("reconcile-text: {reconcile_result:?}");
println!();
}
/// Demonstrates cases where diff-match-patch silently produces incorrect
/// output, while reconcile-text preserves both users' edits correctly
///
/// Run it with:
/// `cargo run --example compare-with-diff-match-patch`
fn main() {
// Example 1
// Two users edit the same short phrase. Alice replaces "old(!)" with
// "new improved", Bob replaces "broken" with "working". These are
// independent changes to adjacent words.
//
// diff-match-patch has no common ancestor, so it diffs parent → left
// and applies the patch to right. The character-level patches overlap
// and produce garbled text ("impovind"). It reports success.
//
// reconcile-text sees both changes relative to the parent and merges
// them cleanly.
println!("── Example 1: adjacent edits ──");
try_merge(
"old(!) broken code",
"new improved code",
"old(!) working code",
);
// Example 2
// Alice adds a sentence. Bob rewrites the surrounding text. Because
// diff-match-patch works without a common ancestor, Alice's entire
// sentence is silently lost.
println!("── Example 2: sentence lost ──");
// Alice adds a sentence in the middle of a paragraph. Bob rephrases
// the same paragraph. Because the patch context from Alice's edit no
// longer appears in Bob's version, diff-match-patch silently drops
// Alice's entire sentence.
//
// reconcile-text understands both edits relative to the common ancestor
// and keeps both.
try_merge(
"We used the existing parsing approach for processing. The output was saved to the \
database.",
"We used the existing parsing approach for processing. Always validate the schema! The \
output was saved to the database.",
"We adopted a brand new analysis pipeline for execution. The results were written to \
cloud storage.",
);
}