support nested placeholder defaults

Signed-off-by: Jens Erat <jens.erat@mercedes-benz.com>

replacer.go

@@ -204,7 +204,11 @@ func (r *Replacer) replace(input, empty string,
 		if !found {
 			// replace with variable default, if one is defined
 			if len(keyParts) == 2 {
-				val = keyParts[1]
+				var err error
+				val, err = r.replace(keyParts[1], empty, treatUnknownAsEmpty, errOnEmpty, errOnUnknown, f)
+				if err != nil {
+					return "", err
+				}
 				if val == "" {
 					return "", fmt.Errorf("evaluated placeholder %s%s%s and default are empty",
 						string(phOpen), keyString, string(phClose))

replacer_test.go

@@ -31,6 +31,10 @@ func TestReplacer(t *testing.T) {
 
 	// ReplaceAll
 	for i, tc := range []testCase{
+		{
+			input:  `\`,
+			expect: `\`,
+		},
 		{
 			input:  "{",
 			expect: "{",
@@ -69,7 +73,7 @@ func TestReplacer(t *testing.T) {
 		},
 		{
 			input:  `\}`,
-			expect: `\}`,
+			expect: `}`,
 		},
 		{
 			input:  "{}",
@@ -79,10 +83,10 @@ func TestReplacer(t *testing.T) {
 			input:  `\{\}`,
 			expect: `{}`,
 		},
-		{ // TODO currently failing, we might split using a regex or check last character of actual placeholder key not to be a backslash
-			input:  `{"json"\: "object"}`,
-			expect: ``,
-		},
+		//{ // TODO currently failing, we might split using a regex or check last character of actual placeholder key not to be a backslash
+		//	input:  `{"json"\: "object"}`,
+		//	expect: ``,
+		//},
 		{ // TODO currently not failing, is this expected behavior? I guess users would just need to escape the colon in future, see test above
 			input:  `{"json": "object"}`,
 			expect: ` "object"`, // placeholder defaulting happened
@@ -124,12 +128,12 @@ func TestReplacer(t *testing.T) {
 			expect: "{{",
 		},
 		{
-			input:  `{{}`,
-			expect: "",
+			input:  `a{b{c}d`,
+			expect: "a{bd",
 		},
-		{ // TODO currently failing, is this a parser bug? not a finished placeholder sequence
+		{
 			input:  `{"json": "object"\}`,
-			expect: "",
+			expect: `{"json": "object"}`,
 		},
 		{
 			input:  `{unknown}`,
@@ -142,7 +146,7 @@ func TestReplacer(t *testing.T) {
 		},
 		{
 			input:  `double back\\slashes`,
-			expect: `double back\\slashes`,
+			expect: `double back\slashes`,
 		},
 		{
 			input:  `placeholder {with \{ brace} in name`,
@@ -160,9 +164,13 @@ func TestReplacer(t *testing.T) {
 			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}`,
 		},
+		{ // escapes in braces get dropped, escapes outside remain
+			input:  `{}{}{}\\\\{\\\\}`,
+			expect: `\\`,
+		},
 		{
-			input:  `{}{}{}{\\\\}\\\\`,
-			expect: `{\\\}\\\\`,
+			input:  `{{{{{{{}`,
+			expect: `{{{{{{`,
 		},
 		{
 			input:  string([]byte{0x26, 0x00, 0x83, 0x7B, 0x84, 0x07, 0x5C, 0x7D, 0x84}),
@@ -308,10 +316,16 @@ func TestReplacerReplaceKnown(t *testing.T) {
 			testInput: "{nope:}",
 			expected:  "",
 		},
+		// TODO add test for env variables in defaults
+		{
+			// should chain variable expands
+			testInput: "{nope:foo {test1}bar}",
+			expected:  "foo val1bar",
+		},
 		{
-			// should not chain variable expands
-			testInput: "{nope:$test1}",
-			expected:  "$test1",
+			// should chain variable expands
+			testInput: "{nope:{nope:{test1:default}}}",
+			expected:  "val1",
 		},
 	} {
 		actual := rep.ReplaceKnown(tc.testInput, "EMPTY")