From 6c4d00aad58c72015941ab86c042b3db1d3f7df9 Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Mon, 7 Jan 2019 22:01:40 -0800
Subject: [PATCH] Print diffs when tests fail

---
 Cargo.lock      |  7 +++++++
 cli/Cargo.toml  |  1 +
 cli/src/main.rs |  8 ++------
 cli/src/test.rs | 29 +++++++++++++++++++++++++----
 4 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 7a249312..db86e43b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -156,6 +156,11 @@ dependencies = [
  "cfg-if 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "difference"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "dirs"
 version = "1.0.4"
@@ -643,6 +648,7 @@ version = "0.1.0"
 dependencies = [
  "ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "clap 2.32.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "difference 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "dirs 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "hashbrown 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "ignore 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -764,6 +770,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum crossbeam-epoch 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)" = "2449aaa4ec7ef96e5fb24db16024b935df718e9ae1cec0a1e68feeca2efca7b8"
 "checksum crossbeam-utils 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)" = "677d453a17e8bd2b913fa38e8b9cf04bcdbb5be790aa294f2389661d72036015"
 "checksum crossbeam-utils 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)" = "c55913cc2799171a550e307918c0a360e8c16004820291bf3b638969b4a01816"
+"checksum difference 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "524cbf6897b527295dff137cec09ecf3a05f4fddffd7dfcd1585403449e74198"
 "checksum dirs 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "88972de891f6118092b643d85a0b28e0678e0f948d7f879aa32f2d5aafe97d2a"
 "checksum failure 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "6dd377bcc1b1b7ce911967e3ec24fa19c3224394ec05b54aa7b083d498341ac7"
 "checksum failure_derive 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "64c2d913fe8ed3b6c6518eedf4538255b989945c14c2a7d5cbff62a5e2120596"
diff --git a/cli/Cargo.toml b/cli/Cargo.toml
index 200fd2f1..a2f546c4 100644
--- a/cli/Cargo.toml
+++ b/cli/Cargo.toml
@@ -10,6 +10,7 @@ path = "src/main.rs"
 
 [dependencies]
 ansi_term = "0.11"
+difference = "2.0"
 lazy_static = "1.2.0"
 smallbitvec = "2.3.0"
 clap = "2.32"
diff --git a/cli/src/main.rs b/cli/src/main.rs
index 6a0cf9ec..626a729c 100644
--- a/cli/src/main.rs
+++ b/cli/src/main.rs
@@ -74,9 +74,7 @@ fn run() -> error::Result<()> {
             generate::generate_parser_for_grammar(&grammar_path, minimize, state_ids_to_log)?;
         println!("{}", code);
         return Ok(());
-    }
-
-    if let Some(_matches) = matches.subcommand_matches("test") {
+    } else if let Some(_matches) = matches.subcommand_matches("test") {
         let corpus_path = current_dir.join("corpus");
         let home_dir = dirs::home_dir().unwrap();
         let mut loader = Loader::new(home_dir.join(".tree-sitter"));
@@ -85,9 +83,7 @@ fn run() -> error::Result<()> {
         } else {
             eprintln!("No language found");
         }
-    }
-
-    if let Some(matches) = matches.subcommand_matches("parse") {
+    } else if let Some(matches) = matches.subcommand_matches("parse") {
         loader.find_parsers(&vec![home_dir.join("github")])?;
         let source_path = Path::new(matches.value_of("path").unwrap());
         if let Some((language, _)) = loader.language_for_file_name(source_path)? {
diff --git a/cli/src/test.rs b/cli/src/test.rs
index 7ef63bb7..a693576d 100644
--- a/cli/src/test.rs
+++ b/cli/src/test.rs
@@ -1,5 +1,6 @@
 use super::error::Result;
 use ansi_term::Colour;
+use difference::{Changeset, Difference};
 use regex::bytes::{Regex as ByteRegex, RegexBuilder as ByteRegexBuilder};
 use regex::Regex;
 use std::char;
@@ -55,10 +56,30 @@ pub fn run_tests_at_path(language: Language, path: &Path) -> Result<()> {
             println!("{} failures:", failures.len())
         }
 
-        for (name, actual, expected) in failures {
-            println!("\n  {}:", name);
-            println!("    Expected: {}", expected);
-            println!("    Actual: {}", actual);
+        println!(
+            "\n{} / {}",
+            Colour::Green.paint("expected"),
+            Colour::Red.paint("actual")
+        );
+
+        for (i, (name, actual, expected)) in failures.iter().enumerate() {
+            println!("\n  {}. {}:", i + 1, name);
+            let changeset = Changeset::new(actual, expected, " ");
+            print!("    ");
+            for diff in &changeset.diffs {
+                match diff {
+                    Difference::Same(part) => {
+                        print!("{}{}", part, changeset.split);
+                    }
+                    Difference::Add(part) => {
+                        print!("{}{}", Colour::Green.paint(part), changeset.split);
+                    }
+                    Difference::Rem(part) => {
+                        print!("{}{}", Colour::Red.paint(part), changeset.split);
+                    }
+                }
+            }
+            println!("");
         }
     }