Handle field names with non alphanumeric characters (#99)

When supplying a payload of {"-1":"Fails"} the fieldname will be 1.
This will fail when running gofmt(and is not a valid go identifier).
This change checks if the sanitized field name is a number. If so it will preprend Num.

To avoid duplicate field names because of sanitizing values the code now keeps a map with used
fields for the current struct.

Author: wvell

json-to-go.js

@@ -169,6 +169,8 @@ function jsonToGo(json, typename, flatten = true)
 			)
 		}
 
+		const seenTypeNames = [];
+
 		if (flatten && depth >= 2)
 		{
 			const parentType = `type ${parent}`;
@@ -190,7 +192,9 @@ function jsonToGo(json, typename, flatten = true)
 			{
 				const keyname = getOriginalName(keys[i]);
 				indenter(innerTabs)
-				const typename = format(keyname)
+				const typename = uniqueTypeName(format(keyname), seenTypeNames)
+				seenTypeNames.push(typename)
+
 				appender(typename+" ");
 				parent = typename
 				parseScope(scope[keys[i]], depth);
@@ -213,7 +217,8 @@ function jsonToGo(json, typename, flatten = true)
 			{
 				const keyname = getOriginalName(keys[i]);
 				indent(tabs);
-				const typename = format(keyname);
+				const typename = uniqueTypeName(format(keyname), seenTypeNames)
+				seenTypeNames.push(typename)
 				append(typename+" ");
 				parent = typename
 				parseScope(scope[keys[i]], depth);
@@ -253,9 +258,41 @@ function jsonToGo(json, typename, flatten = true)
 		stack[stack.length - 1] += str;
 	}
 
+	// Generate a unique name to avoid duplicate struct field names.
+	// This function appends a number at the end of the field name.
+	function uniqueTypeName(name, seen) {
+		if (seen.indexOf(name) === -1) {
+			return name;
+		}
+
+		let i = 0;
+		while (true) {
+			let newName = name + i.toString();
+			if (seen.indexOf(newName) === -1) {
+				return newName;
+			}
+
+			i++;
+		}
+	}
+
 	// Sanitizes and formats a string to make an appropriate identifier in Go
 	function format(str)
 	{
+		str = formatNumber(str);
+
+		let sanitized = toProperCase(str).replace(/[^a-z0-9]/ig, "")
+		if (!sanitized) {
+			return "NAMING_FAILED";
+		}
+
+		// After sanitizing the remaining characters can start with a number.
+		// Run the sanitized string again trough formatNumber to make sure the identifier is Num[0-9] or Zero_... instead of 1.
+		return formatNumber(sanitized)
+	}
+
+	// Adds a prefix to a number to make an appropriate identifier in Go
+	function formatNumber(str) {
 		if (!str)
 			return "";
 		else if (str.match(/^\d+$/))
@@ -267,7 +304,8 @@ function jsonToGo(json, typename, flatten = true)
 				'8': "Eight_", '9': "Nine_"};
 			str = numbers[str.charAt(0)] + str.substr(1);
 		}
-		return toProperCase(str).replace(/[^a-z0-9]/ig, "") || "NAMING_FAILED";
+
+		return str;
 	}
 
 	// Determines the most appropriate Go type
@@ -324,12 +362,12 @@ function jsonToGo(json, typename, flatten = true)
 		if (str.match(/^[_A-Z0-9]+$/)) {
 			str = str.toLowerCase();
 		}
-		
+
 		// https://github.com/golang/lint/blob/5614ed5bae6fb75893070bdc0996a68765fdd275/lint.go#L771-L810
 		const commonInitialisms = [
-			"ACL", "API", "ASCII", "CPU", "CSS", "DNS", "EOF", "GUID", "HTML", "HTTP", 
-			"HTTPS", "ID", "IP", "JSON", "LHS", "QPS", "RAM", "RHS", "RPC", "SLA", 
-			"SMTP", "SQL", "SSH", "TCP", "TLS", "TTL", "UDP", "UI", "UID", "UUID", 
+			"ACL", "API", "ASCII", "CPU", "CSS", "DNS", "EOF", "GUID", "HTML", "HTTP",
+			"HTTPS", "ID", "IP", "JSON", "LHS", "QPS", "RAM", "RHS", "RPC", "SLA",
+			"SMTP", "SQL", "SSH", "TCP", "TLS", "TTL", "UDP", "UI", "UID", "UUID",
 			"URI", "URL", "UTF8", "VM", "XML", "XMPP", "XSRF", "XSS"
 		];
 

json-to-go.test.js

@@ -48,6 +48,11 @@ function test() {
       input: '{"PUBLIC_IP": ""}',
       expected:
         'type AutoGenerated struct {\n\tPublicIP string `json:"PUBLIC_IP"`\n}'
+    },
+    {
+      input: '{"+1": "Fails", "-1": "This should not cause duplicate field name"}',
+      expected:
+        'type AutoGenerated struct {\n\tNum1 string `json:"+1"`\n\tNum10 string `json:"-1"`\n}'
     }
   ];