Fix #12280: replace difference crate with similar (#12282)

Fixes #12280.

# Description

This removes the dependency on the `difference` crate, which is
unmaintained, for `nu-plugin-test-support`. The `similar` crate
(Apache-2.0) is used instead, which is a bit larger and more complex,
but still suitable for a dev dep for tests. Also switched to use
`crossterm` for colors, since `similar` doesn't come with any terminal
pretty printing functionality.

# User-Facing Changes

None - output should be identical.

# Tests + Formatting
- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

Cargo.lock

@@ -1101,12 +1101,6 @@ version = "0.1.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "56254986775e3233ffa9c4d7d3faaf6d36a2c09d30b20687e9f88bc8bafc16c8"
 
-[[package]]
-name = "difference"
-version = "2.0.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "524cbf6897b527295dff137cec09ecf3a05f4fddffd7dfcd1585403449e74198"
-
 [[package]]
 name = "difflib"
 version = "0.4.0"
@@ -3097,12 +3091,13 @@ dependencies = [
 name = "nu-plugin-test-support"
 version = "0.91.1"
 dependencies = [
- "difference",
+ "nu-ansi-term",
  "nu-engine",
  "nu-parser",
  "nu-plugin",
  "nu-protocol",
  "serde",
+ "similar",
  "typetag",
 ]
 

crates/nu-plugin-test-support/Cargo.toml

@@ -12,7 +12,8 @@ nu-engine = { path = "../nu-engine", version = "0.91.1", features = ["plugin"] }
 nu-protocol = { path = "../nu-protocol", version = "0.91.1", features = ["plugin"] }
 nu-parser = { path = "../nu-parser", version = "0.91.1", features = ["plugin"] }
 nu-plugin = { path = "../nu-plugin", version = "0.91.1" }
-difference = "2.0"
+nu-ansi-term = { workspace = true }
+similar = "2.4"
 
 [dev-dependencies]
 typetag = "0.2"

crates/nu-plugin-test-support/src/diff.rs

@@ -0,0 +1,27 @@
+use std::fmt::Write;
+
+use nu_ansi_term::{Color, Style};
+use similar::{ChangeTag, TextDiff};
+
+/// Generate a stylized diff of different lines between two strings
+pub(crate) fn diff_by_line(old: &str, new: &str) -> String {
+    let mut out = String::new();
+
+    let diff = TextDiff::from_lines(old, new);
+
+    for change in diff.iter_all_changes() {
+        let style = match change.tag() {
+            ChangeTag::Equal => Style::new(),
+            ChangeTag::Delete => Color::Red.into(),
+            ChangeTag::Insert => Color::Green.into(),
+        };
+        let _ = write!(
+            out,
+            "{}{}",
+            style.paint(change.tag().to_string()),
+            style.paint(change.value()),
+        );
+    }
+
+    out
+}

crates/nu-plugin-test-support/src/lib.rs

@@ -63,6 +63,7 @@
 //! # test_lowercase().unwrap();
 //! ```
 
+mod diff;
 mod fake_persistent_plugin;
 mod fake_register;
 mod plugin_test;

crates/nu-plugin-test-support/src/plugin_test.rs

@@ -1,6 +1,6 @@
 use std::{convert::Infallible, sync::Arc};
 
-use difference::Changeset;
+use nu_ansi_term::Style;
 use nu_engine::eval_block;
 use nu_parser::parse;
 use nu_plugin::{Plugin, PluginCommand, PluginCustomValue, PluginSource};
@@ -10,7 +10,7 @@ use nu_protocol::{
     report_error_new, LabeledError, PipelineData, PluginExample, ShellError, Span, Value,
 };
 
-use crate::fake_register::fake_register;
+use crate::{diff::diff_by_line, fake_register::fake_register};
 
 /// An object through which plugins can be tested.
 pub struct PluginTest {
@@ -190,10 +190,11 @@ impl PluginTest {
         let mut failed = false;
 
         for example in examples {
+            let bold = Style::new().bold();
             let mut failed_header = || {
                 failed = true;
-                eprintln!("\x1b[1mExample:\x1b[0m {}", example.example);
+                eprintln!("{} {}", bold.paint("Example:"), example.example);
-                eprintln!("\x1b[1mDescription:\x1b[0m {}", example.description);
+                eprintln!("{} {}", bold.paint("Description:"), example.description);
             };
             if let Some(expectation) = &example.result {
                 match self.eval(&example.example) {
@@ -212,12 +213,9 @@ impl PluginTest {
                             // If they're not equal, print a diff of the debug format
                             let expectation_formatted = format!("{:#?}", expectation);
                             let value_formatted = format!("{:#?}", value);
-                            let diff =
+                            let diff = diff_by_line(&expectation_formatted, &value_formatted);
-                                Changeset::new(&expectation_formatted, &value_formatted, "\n");
                             failed_header();
-                            eprintln!("\x1b[1mResult:\x1b[0m {diff}");
+                            eprintln!("{} {}", bold.paint("Result:"), diff);
-                        } else {
-                            println!("{:?}, {:?}", expectation, value);
                         }
                     }
                     Err(err) => {