From e6228b0bf25476276a459a51885e00445a2c8c3a Mon Sep 17 00:00:00 2001
From: Aleksei Androsov <aandrosov@yandex-team.ru>
Date: Thu, 5 Aug 2021 21:46:42 +0300
Subject: [PATCH] fix: Field starting with '_' generates an interface property
 starting with 'undefined'

---
 src/case.ts        |  3 ++-
 tests/case-test.ts | 16 ++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/case.ts b/src/case.ts
index ed90bff75..37656b557 100644
--- a/src/case.ts
+++ b/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());
         }
diff --git a/tests/case-test.ts b/tests/case-test.ts
index cad40a158..33971df4e 100644
--- a/tests/case-test.ts
+++ b/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');
+  });
 });