Align find_all with C#/python approach.

distribution/lib/Standard/Base/0.0.0-dev/src/Data/Text/Regex/Pattern.enso

@@ -353,7 +353,7 @@ type Match_Iterator
        Also returns the next iterator, if there was a match.
     next : Match_Iterator_Value
     next self =
-        regex_result = if self.cursor >= self.input.char_vector.length then Nothing else self.pattern.internal_regex_object.exec self.input self.cursor
+        regex_result = if self.cursor > self.input.char_vector.length then Nothing else self.pattern.internal_regex_object.exec self.input self.cursor
         case regex_result.is_nothing.not && regex_result.isMatch of
             False ->
                 filler_range = Range.new self.cursor (Text_Utils.char_length self.input)
@@ -364,7 +364,8 @@ type Match_Iterator
                 filler_range = Range.new self.cursor match_start
                 filler_span = (Utf_16_Span.Value filler_range self.input)
                 match = Match.Value self.pattern regex_result self.input
-                next_cursor = match.utf_16_end 0
+                ## Handle edge case where match is 0 length
+                next_cursor = (self.cursor + 1).max (match.utf_16_end 0)
                 next_iterator = Match_Iterator.Value self.pattern self.input next_cursor
                 Match_Iterator_Value.Next filler_span match next_iterator
 

test/Tests/src/Data/Text/Regex_Spec.enso

@@ -141,6 +141,15 @@ spec =
             match = pattern.find_all input
             match . should_equal []
 
+        Test.specify "should handle matching empty matches" <|
+            pattern = Regex.compile ".*"
+            pattern.find_all "Hello World" . should_equal ["Hello World", ""]
+            pattern.find_all "" . should_equal [""]
+
+            pattern_2 = Regex.compile ".*(?=.)"
+            pattern_2.find_all "Hello World" . should_equal ["Hello Worl", ""]
+            pattern_2.find_all "" . should_equal []
+
         Test.specify "should correctly handle edge cases where one-letter matches happen at the end of the word" <|
             Regex.compile "(a+|1+)" . find_all "a1a1" . should_equal ["a", "1", "a", "1"]
             Regex.compile "([a]+|[1]+)" . find_all "a1a1" . should_equal ["a", "1", "a", "1"]

test/Tests/src/Data/Text_Spec.enso

@@ -1279,6 +1279,12 @@ spec =
             "Hello World!".find_all ".o" . map (match-> match.span 0) . should_equal [Span.Value (3.up_to 5) "Hello World!", Span.Value (6.up_to 8) "Hello World!"]
             "foobar".find "BAR" Case_Sensitivity.Insensitive . span 0 . should_equal (Span.Value (3.up_to 6) "foobar")
 
+        Test.specify "find_all should handle 0 length matches" <|
+            "Hello World".find_all ".*" . map (_.text) . should_equal ["Hello World", ""]
+            "".find_all ".*" . map (_.text) . should_equal [""]
+            "Hello World".find_all ".*(?=.)" . map (_.text) . should_equal ["Hello Worl", ""]
+            "".find_all ".*(?=.)" . map (_.text) . should_equal []
+
         Test.specify "should handle accents and other multi-point graphemes" <|
             accents = 'a\u{301}e\u{301}o\u{301}he\u{301}h'