Handle empty string in uppercaseFirst and lowercaseFirst

This change allows to handle Solidity fallback function properly:
function() external payable

Author: pdyraga

tools/generators/ethereum/contract_parsing.go

@@ -275,10 +275,18 @@ func buildEventInfo(eventsByName map[string]abi.Event) []eventInfo {
 }
 
 func uppercaseFirst(str string) string {
+	if len(str) == 0 {
+		return str
+	}
+
 	return strings.ToUpper(str[0:1]) + str[1:]
 }
 
 func lowercaseFirst(str string) string {
+	if len(str) == 0 {
+		return str
+	}
+
 	return strings.ToLower(str[0:1]) + str[1:]
 }
 

tools/generators/ethereum/contract_parsing_test.go

@@ -0,0 +1,69 @@
+package main
+
+import "testing"
+
+func TestLowercaseFirst(t *testing.T) {
+	var tests = map[string]struct {
+		input    string
+		expected string
+	}{
+		"empty string": {
+			input:    "",
+			expected: "",
+		},
+		"first lower case": {
+			input:    "helloWorld",
+			expected: "helloWorld",
+		},
+		"first upper case": {
+			input:    "HelloWorld",
+			expected: "helloWorld",
+		},
+	}
+
+	for testName, test := range tests {
+		t.Run(testName, func(t *testing.T) {
+			actual := lowercaseFirst(test.input)
+			if actual != test.expected {
+				t.Errorf(
+					"unexpected output\nexpected: [%v]\nactual:   [%v]",
+					test.expected,
+					actual,
+				)
+			}
+		})
+	}
+}
+
+func TestUppercaseFirst(t *testing.T) {
+	var tests = map[string]struct {
+		input    string
+		expected string
+	}{
+		"empty string": {
+			input:    "",
+			expected: "",
+		},
+		"first upper case": {
+			input:    "HelloWorld",
+			expected: "HelloWorld",
+		},
+		"first lower case": {
+			input:    "helloWorld",
+			expected: "HelloWorld",
+		},
+	}
+
+	for testName, test := range tests {
+		t.Run(testName, func(t *testing.T) {
+			actual := uppercaseFirst(test.input)
+			if actual != test.expected {
+				t.Errorf(
+					"unexpected output\nexpected: [%v]\nactual:   [%v]",
+					test.expected,
+					actual,
+				)
+			}
+		})
+	}
+}