From 12dc29877a6a1d44c3117a7430c4e0427df232b6 Mon Sep 17 00:00:00 2001
From: Andrew Gallant <jamslam@gmail.com>
Date: Mon, 6 Mar 2023 13:23:45 -0500
Subject: [PATCH] api: improve Debug impl for Match

This makes it so the Debug impl for Match only shows the actual matched
text. Otherwise, the Match shows the entire haystack, which is likely to
be misleading.

Fixes #514
---
 src/re_bytes.rs   | 20 +++++++++++++++++++-
 src/re_unicode.rs | 12 +++++++++++-
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/src/re_bytes.rs b/src/re_bytes.rs
index fcc9cd5bb..e3a3b019b 100644
--- a/src/re_bytes.rs
+++ b/src/re_bytes.rs
@@ -17,7 +17,7 @@ use crate::re_trait::{self, RegularExpression, SubCapturesPosIter};
 /// Match represents a single match of a regex in a haystack.
 ///
 /// The lifetime parameter `'t` refers to the lifetime of the matched text.
-#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+#[derive(Copy, Clone, Eq, PartialEq)]
 pub struct Match<'t> {
     text: &'t [u8],
     start: usize,
@@ -69,6 +69,24 @@ impl<'t> Match<'t> {
     }
 }
 
+impl<'t> std::fmt::Debug for Match<'t> {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        let mut fmt = f.debug_struct("Match");
+        fmt.field("start", &self.start).field("end", &self.end);
+        if let Ok(s) = std::str::from_utf8(self.as_bytes()) {
+            fmt.field("bytes", &s);
+        } else {
+            // FIXME: It would be nice if this could be printed as a string
+            // with invalid UTF-8 replaced with hex escapes. A alloc would
+            // probably okay if that makes it easier, but regex-automata does
+            // (at time of writing) have internal routines that do this. So
+            // maybe we should expose them.
+            fmt.field("bytes", &self.as_bytes());
+        }
+        fmt.finish()
+    }
+}
+
 impl<'t> From<Match<'t>> for Range<usize> {
     fn from(m: Match<'t>) -> Range<usize> {
         m.range()
diff --git a/src/re_unicode.rs b/src/re_unicode.rs
index 296736080..57689086d 100644
--- a/src/re_unicode.rs
+++ b/src/re_unicode.rs
@@ -25,7 +25,7 @@ pub fn escape(text: &str) -> String {
 /// Match represents a single match of a regex in a haystack.
 ///
 /// The lifetime parameter `'t` refers to the lifetime of the matched text.
-#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+#[derive(Copy, Clone, Eq, PartialEq)]
 pub struct Match<'t> {
     text: &'t str,
     start: usize,
@@ -77,6 +77,16 @@ impl<'t> Match<'t> {
     }
 }
 
+impl<'t> std::fmt::Debug for Match<'t> {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        f.debug_struct("Match")
+            .field("start", &self.start)
+            .field("end", &self.end)
+            .field("string", &self.as_str())
+            .finish()
+    }
+}
+
 impl<'t> From<Match<'t>> for &'t str {
     fn from(m: Match<'t>) -> &'t str {
         m.as_str()