Allow escaping meta characters with backslashes

One can escape meta characters in extended-search mode with backslashes.

  Prefixes:
    \'
    \!
    \^

  Suffix:
    \$

  Term separator:
    \<SPACE>

To keep things simple, we are not going to support escaping of escaped
sequences (e.g. \\') for matching them literally.

Since this is a breaking change, we will bump the minor version.

Close #444

3 files changed, 41 insertions, 22 deletions

diff --git a/src/pattern.go b/src/pattern.go
index 47cabf78..34329306 100644
--- a/src/pattern.go
+++ b/src/pattern.go
@@ -53,13 +53,15 @@ type Pattern struct {
 }
 
 var (
-	_patternCache map[string]*Pattern
-	_splitRegex   *regexp.Regexp
-	_cache        ChunkCache
+	_patternCache       map[string]*Pattern
+	_splitRegex         *regexp.Regexp
+	_escapedPrefixRegex *regexp.Regexp
+	_cache              ChunkCache
 )
 
 func init() {
-	_splitRegex = regexp.MustCompile("\\s+")
+	_splitRegex = regexp.MustCompile(" +")
+	_escapedPrefixRegex = regexp.MustCompile("^\\\\['!^]")
 	clearPatternCache()
 	clearChunkCache()
 }
@@ -80,7 +82,10 @@ func BuildPattern(fuzzy bool, fuzzyAlgo algo.Algo, extended bool, caseMode Case,
 
 	var asString string
 	if extended {
-		asString = strings.Trim(string(runes), " ")
+		asString = strings.TrimLeft(string(runes), " ")
+		for strings.HasSuffix(asString, " ") && !strings.HasSuffix(asString, "\\ ") {
+			asString = asString[:len(asString)-1]
+		}
 	} else {
 		asString = string(runes)
 	}
@@ -140,12 +145,13 @@ func BuildPattern(fuzzy bool, fuzzyAlgo algo.Algo, extended bool, caseMode Case,
 }
 
 func parseTerms(fuzzy bool, caseMode Case, normalize bool, str string) []termSet {
+	str = strings.Replace(str, "\\ ", "\t", -1)
 	tokens := _splitRegex.Split(str, -1)
 	sets := []termSet{}
 	set := termSet{}
 	switchSet := false
 	for _, token := range tokens {
-		typ, inv, text := termFuzzy, false, token
+		typ, inv, text := termFuzzy, false, strings.Replace(token, "\t", " ", -1)
 		lowerText := strings.ToLower(text)
 		caseSensitive := caseMode == CaseRespect ||
 			caseMode == CaseSmart && text != lowerText
@@ -167,6 +173,15 @@ func parseTerms(fuzzy bool, caseMode Case, normalize bool, str string) []termSet
 			text = text[1:]
 		}
 
+		if strings.HasSuffix(text, "$") {
+			if strings.HasSuffix(text, "\\$") {
+				text = text[:len(text)-2] + "$"
+			} else {
+				typ = termSuffix
+				text = text[:len(text)-1]
+			}
+		}
+
 		if strings.HasPrefix(text, "'") {
 			// Flip exactness
 			if fuzzy && !inv {
@@ -177,16 +192,16 @@ func parseTerms(fuzzy bool, caseMode Case, normalize bool, str string) []termSet
 				text = text[1:]
 			}
 		} else if strings.HasPrefix(text, "^") {
-			if strings.HasSuffix(text, "$") {
+			if typ == termSuffix {
 				typ = termEqual
-				text = text[1 : len(text)-1]
 			} else {
 				typ = termPrefix
-				text = text[1:]
 			}
-		} else if strings.HasSuffix(text, "$") {
-			typ = termSuffix
-			text = text[:len(text)-1]
+			text = text[1:]
+		}
+
+		if _escapedPrefixRegex.MatchString(text) {
+			text = text[1:]
 		}
 
 		if len(text) > 0 {
@@ -236,7 +251,7 @@ func (p *Pattern) CacheKey() string {
 			cacheableTerms = append(cacheableTerms, string(termSet[0].text))
 		}
 	}
-	return strings.Join(cacheableTerms, " ")
+	return strings.Join(cacheableTerms, "\t")
 }
 
 // Match returns the list of matches Items in the given Chunk
diff --git a/src/pattern_test.go b/src/pattern_test.go
index 9d56ff9f..efb1ef2d 100644
--- a/src/pattern_test.go
+++ b/src/pattern_test.go
@@ -165,15 +165,15 @@ func TestCacheKey(t *testing.T) {
 			t.Errorf("Expected: %s, actual: %s", expected, pat.CacheKey())
 		}
 		if pat.cacheable != cacheable {
-			t.Errorf("Expected: %s, actual: %s (%s)", cacheable, pat.cacheable, patStr)
+			t.Errorf("Expected: %t, actual: %t (%s)", cacheable, pat.cacheable, patStr)
 		}
 		clearPatternCache()
 	}
 	test(false, "foo !bar", "foo !bar", true)
 	test(false, "foo | bar !baz", "foo | bar !baz", true)
-	test(true, "foo  bar  baz", "foo bar baz", true)
+	test(true, "foo  bar  baz", "foo\tbar\tbaz", true)
 	test(true, "foo !bar", "foo", false)
-	test(true, "foo !bar   baz", "foo baz", false)
+	test(true, "foo !bar   baz", "foo\tbaz", false)
 	test(true, "foo | bar baz", "baz", false)
 	test(true, "foo | bar | baz", "", false)
 	test(true, "foo | bar !baz", "", false)
@@ -192,11 +192,11 @@ func TestCacheable(t *testing.T) {
 		}
 		clearPatternCache()
 	}
-	test(true, "foo bar", "foo bar", true)
-	test(true, "foo 'bar", "foo bar", false)
+	test(true, "foo bar", "foo\tbar", true)
+	test(true, "foo 'bar", "foo\tbar", false)
 	test(true, "foo !bar", "foo", false)
 
-	test(false, "foo bar", "foo bar", true)
+	test(false, "foo bar", "foo\tbar", true)
 	test(false, "foo 'bar", "foo", false)
 	test(false, "foo '", "foo", true)
 	test(false, "foo 'bar", "foo", false)
diff --git a/src/terminal.go b/src/terminal.go
index 8c7c1a8d..5c66f44f 100644
--- a/src/terminal.go
+++ b/src/terminal.go
@@ -281,9 +281,13 @@ func defaultKeymap() map[int][]action {
 	return keymap
 }
 
+func trimQuery(query string) []rune {
+	return []rune(strings.Replace(query, "\t", " ", -1))
+}
+
 // NewTerminal returns new Terminal object
 func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
-	input := []rune(opts.Query)
+	input := trimQuery(opts.Query)
 	var header []string
 	if opts.Reverse {
 		header = opts.Header
@@ -1694,13 +1698,13 @@ func (t *Terminal) Loop() {
 			case actPreviousHistory:
 				if t.history != nil {
 					t.history.override(string(t.input))
-					t.input = []rune(t.history.previous())
+					t.input = trimQuery(t.history.previous())
 					t.cx = len(t.input)
 				}
 			case actNextHistory:
 				if t.history != nil {
 					t.history.override(string(t.input))
-					t.input = []rune(t.history.next())
+					t.input = trimQuery(t.history.next())
 					t.cx = len(t.input)
 				}
 			case actSigStop: