Implement exact-boundary match type

Close #3963

3 files changed, 38 insertions, 11 deletions

diff --git a/README.md b/README.md
index 1ee10581..950cf40a 100644
--- a/README.md
+++ b/README.md
@@ -376,15 +376,16 @@ Unless otherwise specified, fzf starts in "extended-search mode" where you can
 type in multiple search terms delimited by spaces. e.g. `^music .mp3$ sbtrkt
 !fire`
 
-| Token     | Match type                 | Description                          |
-| --------- | -------------------------- | ------------------------------------ |
-| `sbtrkt`  | fuzzy-match                | Items that match `sbtrkt`            |
-| `'wild`   | exact-match (quoted)       | Items that include `wild`            |
-| `^music`  | prefix-exact-match         | Items that start with `music`        |
-| `.mp3$`   | suffix-exact-match         | Items that end with `.mp3`           |
-| `!fire`   | inverse-exact-match        | Items that do not include `fire`     |
-| `!^music` | inverse-prefix-exact-match | Items that do not start with `music` |
-| `!.mp3$`  | inverse-suffix-exact-match | Items that do not end with `.mp3`    |
+| Token     | Match type                              | Description                                  |
+| --------- | --------------------------------------  | ------------------------------------------   |
+| `sbtrkt`  | fuzzy-match                             | Items that match `sbtrkt`                    |
+| `'wild`   | exact-match (quoted)                    | Items that include `wild`                    |
+| `'wild'`  | exact-boundary-match (quoted both ends) | Items that include `wild` at word boundaries |
+| `^music`  | prefix-exact-match                      | Items that start with `music`                |
+| `.mp3$`   | suffix-exact-match                      | Items that end with `.mp3`                   |
+| `!fire`   | inverse-exact-match                     | Items that do not include `fire`             |
+| `!^music` | inverse-prefix-exact-match              | Items that do not start with `music`         |
+| `!.mp3$`  | inverse-suffix-exact-match              | Items that do not end with `.mp3`            |
 
 If you don't prefer fuzzy matching and do not wish to "quote" every word,
 start fzf with `-e` or `--exact` option. Note that when  `--exact` is set,
diff --git a/src/algo/algo.go b/src/algo/algo.go
index c85ec82e..a02a0a81 100644
--- a/src/algo/algo.go
+++ b/src/algo/algo.go
@@ -798,6 +798,14 @@ func FuzzyMatchV1(caseSensitive bool, normalize bool, forward bool, text *util.C
 // The solution is much cheaper since there is only one possible alignment of
 // the pattern.
 func ExactMatchNaive(caseSensitive bool, normalize bool, forward bool, text *util.Chars, pattern []rune, withPos bool, slab *util.Slab) (Result, *[]int) {
+	return exactMatchNaive(caseSensitive, normalize, forward, false, text, pattern, withPos, slab)
+}
+
+func ExactMatchBoundary(caseSensitive bool, normalize bool, forward bool, text *util.Chars, pattern []rune, withPos bool, slab *util.Slab) (Result, *[]int) {
+	return exactMatchNaive(caseSensitive, normalize, forward, true, text, pattern, withPos, slab)
+}
+
+func exactMatchNaive(caseSensitive bool, normalize bool, forward bool, boundaryCheck bool, text *util.Chars, pattern []rune, withPos bool, slab *util.Slab) (Result, *[]int) {
 	if len(pattern) == 0 {
 		return Result{0, 0, 0}, nil
 	}
@@ -832,10 +840,19 @@ func ExactMatchNaive(caseSensitive bool, normalize bool, forward bool, text *uti
 		}
 		pidx_ := indexAt(pidx, lenPattern, forward)
 		pchar := pattern[pidx_]
-		if pchar == char {
+		ok := pchar == char
+		if ok {
 			if pidx_ == 0 {
 				bonus = bonusAt(text, index_)
 			}
+			if boundaryCheck {
+				ok = bonus >= bonusBoundary
+				if ok && pidx_ == len(pattern)-1 {
+					ok = index_ == lenRunes-1 || charClassOf(text.Get(index_+1)) <= charDelimiter
+				}
+			}
+		}
+		if ok {
 			pidx++
 			if pidx == lenPattern {
 				if bonus > bestBonus {
diff --git a/src/pattern.go b/src/pattern.go
index ee1b88a5..c736be3c 100644
--- a/src/pattern.go
+++ b/src/pattern.go
@@ -23,6 +23,7 @@ type termType int
 const (
 	termFuzzy termType = iota
 	termExact
+	termExactBoundary
 	termPrefix
 	termSuffix
 	termEqual
@@ -147,6 +148,7 @@ func BuildPattern(cache *ChunkCache, patternCache map[string]*Pattern, fuzzy boo
 	ptr.procFun[termFuzzy] = fuzzyAlgo
 	ptr.procFun[termEqual] = algo.EqualMatch
 	ptr.procFun[termExact] = algo.ExactMatchNaive
+	ptr.procFun[termExactBoundary] = algo.ExactMatchBoundary
 	ptr.procFun[termPrefix] = algo.PrefixMatch
 	ptr.procFun[termSuffix] = algo.SuffixMatch
 
@@ -193,7 +195,14 @@ func parseTerms(fuzzy bool, caseMode Case, normalize bool, str string) []termSet
 			text = text[:len(text)-1]
 		}
 
-		if strings.HasPrefix(text, "'") {
+		if fuzzy && len(text) > 2 && strings.HasPrefix(text, "'") && strings.HasSuffix(text, "'") ||
+			!fuzzy && !strings.HasPrefix(text, "'") && strings.HasSuffix(text, "'") {
+			typ = termExactBoundary
+			if fuzzy {
+				text = text[1:]
+			}
+			text = text[:len(text)-1]
+		} else if strings.HasPrefix(text, "'") {
 			// Flip exactness
 			if fuzzy && !inv {
 				typ = termExact