Rework Replacer loop to handle escaped braces (#3121)

Fixes #3116

* Rework Replacer loop to ignore escaped braces

* Add benchmark tests for replacer

* Optimise handling of escaped braces

* Handle escaped closing braces

* Remove additional check for closing brace

This commit removes the additional check for input in which the closing
brace appears before the opening brace. This check has been removed for
performance reasons as it is deemed an unlikely edge case.

* Check for escaped closing braces in placeholder name

1 files changed, 113 insertions, 0 deletions

diff --git a/replacer_test.go b/replacer_test.go
index 4b56194..66bb537 100644
--- a/replacer_test.go
+++ b/replacer_test.go
@@ -36,30 +36,86 @@ func TestReplacer(t *testing.T) {
 			expect: "{",
 		},
 		{
+			input:  `\{`,
+			expect: `{`,
+		},
+		{
 			input:  "foo{",
 			expect: "foo{",
 		},
 		{
+			input:  `foo\{`,
+			expect: `foo{`,
+		},
+		{
 			input:  "foo{bar",
 			expect: "foo{bar",
 		},
 		{
+			input:  `foo\{bar`,
+			expect: `foo{bar`,
+		},
+		{
 			input:  "foo{bar}",
 			expect: "foo",
 		},
 		{
+			input:  `foo\{bar\}`,
+			expect: `foo{bar}`,
+		},
+		{
 			input:  "}",
 			expect: "}",
 		},
 		{
+			input:  `\}`,
+			expect: `\}`,
+		},
+		{
 			input:  "{}",
 			expect: "",
 		},
 		{
+			input:  `\{\}`,
+			expect: `{}`,
+		},
+		{
 			input:  `{"json": "object"}`,
 			expect: "",
 		},
 		{
+			input:  `\{"json": "object"}`,
+			expect: `{"json": "object"}`,
+		},
+		{
+			input:  `\{"json": "object"\}`,
+			expect: `{"json": "object"}`,
+		},
+		{
+			input:  `\{"json": "object{bar}"\}`,
+			expect: `{"json": "object"}`,
+		},
+		{
+			input:  `\{"json": \{"nested": "object"\}\}`,
+			expect: `{"json": {"nested": "object"}}`,
+		},
+		{
+			input:  `\{"json": \{"nested": "{bar}"\}\}`,
+			expect: `{"json": {"nested": ""}}`,
+		},
+		{
+			input:  `pre \{"json": \{"nested": "{bar}"\}\}`,
+			expect: `pre {"json": {"nested": ""}}`,
+		},
+		{
+			input:  `\{"json": \{"nested": "{bar}"\}\} post`,
+			expect: `{"json": {"nested": ""}} post`,
+		},
+		{
+			input:  `pre \{"json": \{"nested": "{bar}"\}\} post`,
+			expect: `pre {"json": {"nested": ""}} post`,
+		},
+		{
 			input:  `{{`,
 			expect: "{{",
 		},
@@ -68,10 +124,38 @@ func TestReplacer(t *testing.T) {
 			expect: "",
 		},
 		{
+			input:  `{"json": "object"\}`,
+			expect: "",
+		},
+		{
 			input:  `{unknown}`,
 			empty:  "-",
 			expect: "-",
 		},
+		{
+			input:  `back\slashes`,
+			expect: `back\slashes`,
+		},
+		{
+			input:  `double back\\slashes`,
+			expect: `double back\\slashes`,
+		},
+		{
+			input:  `placeholder {with \{ brace} in name`,
+			expect: `placeholder  in name`,
+		},
+		{
+			input:  `placeholder {with \} brace} in name`,
+			expect: `placeholder  in name`,
+		},
+		{
+			input:  `placeholder {with \} \} braces} in name`,
+			expect: `placeholder  in name`,
+		},
+		{
+			input:  `\{'group':'default','max_age':3600,'endpoints':[\{'url':'https://some.domain.local/a/d/g'\}],'include_subdomains':true\}`,
+			expect: `{'group':'default','max_age':3600,'endpoints':[{'url':'https://some.domain.local/a/d/g'}],'include_subdomains':true}`,
+		},
 	} {
 		actual := rep.ReplaceAll(tc.input, tc.empty)
 		if actual != tc.expect {
@@ -81,6 +165,35 @@ func TestReplacer(t *testing.T) {
 	}
 }
 
+func BenchmarkReplacer(b *testing.B) {
+	type testCase struct {
+		name, input, empty string
+	}
+
+	rep := testReplacer()
+
+	for _, bm := range []testCase{
+		{
+			name:  "no placeholder",
+			input: `simple string`,
+		},
+		{
+			name:  "placeholder",
+			input: `{"json": "object"}`,
+		},
+		{
+			name:  "escaped placeholder",
+			input: `\{"json": \{"nested": "{bar}"\}\}`,
+		},
+	} {
+		b.Run(bm.name, func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				rep.ReplaceAll(bm.input, bm.empty)
+			}
+		})
+	}
+}
+
 func TestReplacerSet(t *testing.T) {
 	rep := testReplacer()