api: fix for split() not returning last ""

Corrects `/-/.split("a-")` to return `["a", ""]` instead of `["a"]`.
(`/-/` is shorthand for `Regex::new("-").unwrap()`.)

This adds tests for both `split()` and `splitn()` covering a variety of
edge cases. One test is commented out because it is failing due to #521.
A future commit will fix it.

Note that the `split2` and `split3` tests were passing incorrectly
before this change. I have fixed them to expect the correct values.

Fixes #627

Author: danielparks

CHANGELOG.md

@@ -11,6 +11,8 @@ Bug fixes:
 
 * [BUG #594](https://github.com/rust-lang/regex/pull/594):
   Improve error reporting when writing `\p\`.
+* [BUG #627](https://github.com/rust-lang/regex/issues/627):
+  Corrects `re.split("a-")` to return `["a", ""]` instead of `["a"]`.
 * [BUG #633](https://github.com/rust-lang/regex/pull/633):
   Squash deprecation warnings for the `std::error::Error::description` method.
 

src/re_bytes.rs

@@ -739,11 +739,11 @@ impl<'r, 't> Iterator for Split<'r, 't> {
         let text = self.finder.0.text();
         match self.finder.next() {
             None => {
-                if self.last >= text.len() {
+                if self.last > text.len() {
                     None
                 } else {
                     let s = &text[self.last..];
-                    self.last = text.len();
+                    self.last = text.len() + 1; // Next call will return None
                     Some(s)
                 }
             }

src/re_unicode.rs

@@ -779,11 +779,11 @@ impl<'r, 't> Iterator for Split<'r, 't> {
         let text = self.finder.0.text();
         match self.finder.next() {
             None => {
-                if self.last >= text.len() {
+                if self.last > text.len() {
                     None
                 } else {
                     let s = &text[self.last..];
-                    self.last = text.len();
+                    self.last = text.len() + 1; // Next call will return None
                     Some(s)
                 }
             }

tests/api.rs

@@ -205,6 +205,20 @@ split!(
     split2,
     r"(?-u)\b",
     "a b c",
-    &[t!(""), t!("a"), t!(" "), t!("b"), t!(" "), t!("c")]
+    &[t!(""), t!("a"), t!(" "), t!("b"), t!(" "), t!("c"), t!("")]
 );
-split!(split3, r"a$", "a", &[t!("")]);
+split!(split3, r"a$", "a", &[t!(""), t!("")]);
+split!(split_none, r"-", r"a", &[t!("a")]);
+split!(split_trailing_blank, r"-", r"a-", &[t!("a"), t!("")]);
+split!(split_trailing_blanks, r"-", r"a--", &[t!("a"), t!(""), t!("")]);
+split!(split_empty, r"-", r"", &[t!("")]);
+
+// See: https://github.com/rust-lang/regex/issues/521
+// splitn!(splitn_below_limit, r"-", r"a", 2, &[t!("a")]);
+
+splitn!(splitn_at_limit, r"-", r"a-b", 2, &[t!("a"), t!("b")]);
+splitn!(splitn_above_limit, r"-", r"a-b-c", 2, &[t!("a"), t!("b-c")]);
+splitn!(splitn_zero_limit, r"-", r"a-b", 0, empty_vec!());
+splitn!(splitn_trailing_blank, r"-", r"a-", 2, &[t!("a"), t!("")]);
+splitn!(splitn_trailing_separator, r"-", r"a--", 2, &[t!("a"), t!("-")]);
+splitn!(splitn_empty, r"-", r"", 1, &[t!("")]);

tests/macros.rs

@@ -147,3 +147,14 @@ macro_rules! split {
         }
     }
 }
+
+macro_rules! splitn {
+    ($name:ident, $re:expr, $text:expr, $limit:expr, $expected:expr) => {
+        #[test]
+        fn $name() {
+            let re = regex!($re);
+            let splitted: Vec<_> = re.splitn(t!($text), $limit).collect();
+            assert_eq!($expected, &*splitted);
+        }
+    }
+}

tests/macros_bytes.rs

@@ -3,6 +3,7 @@ macro_rules! text { ($text:expr) => { $text.as_bytes() } }
 macro_rules! t { ($re:expr) => { text!($re) } }
 macro_rules! match_text { ($text:expr) => { $text.as_bytes() } }
 macro_rules! use_ { ($($path: tt)*) => { use regex::bytes::$($path)*; } }
+macro_rules! empty_vec { () => { <Vec<&[u8]>>::new() } }
 
 macro_rules! bytes { ($text:expr) => { $text } }
 

tests/macros_str.rs

@@ -3,6 +3,7 @@ macro_rules! text { ($text:expr) => { $text } }
 macro_rules! t { ($text:expr) => { text!($text) } }
 macro_rules! match_text { ($text:expr) => { $text.as_str() } }
 macro_rules! use_ { ($($path: tt)*) => { use regex::$($path)*; } }
+macro_rules! empty_vec { () => { <Vec<&str>>::new() } }
 
 macro_rules! no_expand {
     ($text:expr) => {{