fix: Field starting with '_' generates an interface property starting…

… with 'undefined' (#344)

src/case.ts

@@ -6,7 +6,8 @@ export function maybeSnakeToCamel(s: string, options: Pick<Options, 'snakeToCame
       .split('_')
       .map((word, i) => {
         if (i === 0) {
-          return word[0] + word.substring(1).toLowerCase();
+          // if first symbol is "_" then skip it
+          return word ? word[0] + word.substring(1).toLowerCase() : '';
         } else {
           return capitalize(word.toLowerCase());
         }

tests/case-test.ts

@@ -20,4 +20,20 @@ describe('case', () => {
   it('does nothing is already camel', () => {
     expect(maybeSnakeToCamel('FooBar', { snakeToCamel: true })).toEqual('FooBar');
   });
+
+  // deal with original protoc which converts
+  // _uuid -> Uuid
+  // __uuid -> Uuid
+  // _uuid_foo -> UuidFoo
+  it('converts snake to camel with first underscore', () => {
+    expect(maybeSnakeToCamel('_uuid', { snakeToCamel: true })).toEqual('Uuid');
+  });
+
+  it('converts snake to camel with first double underscore', () => {
+    expect(maybeSnakeToCamel('__uuid', { snakeToCamel: true })).toEqual('Uuid');
+  });
+
+  it('converts snake to camel with first underscore and camelize other', () => {
+    expect(maybeSnakeToCamel('_uuid_foo', { snakeToCamel: true })).toEqual('UuidFoo');
+  });
 });