Use pretty_assertions instead of diff in tests (#1776)

The very large diffs from errors in development #1775 caused OOMs so I
figured now's as good a time as any to switch over to using
`pretty_assertions` which other crates in the workspace are already using.

Cargo.toml

@@ -175,7 +175,6 @@ is_executable = { version = "1.0.1", optional = true }
 [dev-dependencies]
 serde_json = "1.0"
 tempfile = "3.1"
-diff = "0.1"
 wast = { path = 'crates/wast' }
 pretty_assertions = { workspace = true }
 libtest-mimic = { workspace = true }

crates/wasmprinter/Cargo.toml

@@ -22,8 +22,4 @@ wasmparser = { workspace = true, features = ['std'] }
 termcolor = { workspace = true }
 
 [dev-dependencies]
-diff = "0.1"
-rayon = { workspace = true }
-tempfile = "3.0"
 wat = { path = "../wat" }
-wast = { path = "../wast" }

tests/roundtrip.rs

@@ -428,27 +428,9 @@ impl TestState {
             // Handle git possibly doing some newline shenanigans on windows.
             let snapshot = snapshot.replace("\r\n", "\n");
             if snapshot != contents {
-                let mut result = String::with_capacity(snapshot.len());
-                for diff in diff::lines(&snapshot, &contents) {
-                    match diff {
-                        diff::Result::Left(s) => {
-                            result.push_str("-");
-                            result.push_str(s);
-                        }
-                        diff::Result::Right(s) => {
-                            result.push_str("+");
-                            result.push_str(s);
-                        }
-                        diff::Result::Both(s, _) => {
-                            result.push_str(" ");
-                            result.push_str(s);
-                        }
-                    }
-                    result.push_str("\n");
-                }
                 anyhow::bail!(
                     "snapshot does not match the expected result, try `env BLESS=1`\n{}",
-                    result
+                    pretty_assertions::StrComparison::new(&snapshot, &contents)
                 );
             }
         }