Fix failure when trying to open empty file (#1126)

Author: igrr

cores/esp8266/spiffs_api.cpp

@@ -410,6 +410,17 @@ class SPIFFSDirImpl : public DirImpl {
 FileImplPtr SPIFFSImpl::open(const char* path, OpenMode openMode, AccessMode accessMode) {
     int mode = getSpiffsMode(openMode, accessMode);
     int fd = SPIFFS_open(&_fs, path, mode, 0);
+    if (fd < 0 && _fs.err_code == SPIFFS_ERR_DELETED && (openMode & OM_CREATE)) {
+        DEBUGV("SPIFFSImpl::open: fd=%d path=`%s` openMode=%d accessMode=%d err=%d, trying to remove\r\n",
+            fd, path, openMode, accessMode, _fs.err_code);
+        auto rc = SPIFFS_remove(&_fs, path);
+        if (rc != SPIFFS_OK) {
+            DEBUGV("SPIFFSImpl::open: SPIFFS_ERR_DELETED, but failed to remove path=`%s` openMode=%d accessMode=%d err=%d\r\n",
+                path, openMode, accessMode, _fs.err_code);
+            return FileImplPtr();
+        }
+        fd = SPIFFS_open(&_fs, path, mode, 0);
+    }
     if (fd < 0) {
         DEBUGV("SPIFFSImpl::open: fd=%d path=`%s` openMode=%d accessMode=%d err=%d\r\n",
             fd, path, openMode, accessMode, _fs.err_code);

tests/FSWrapper/FSWrapper.ino

@@ -139,7 +139,15 @@ void setup() {
       fail("some files left after format");
     }
   }
-
+  {
+    File tmp = SPIFFS.open("/tmp.txt", "w");
+  }
+  {
+    File tmp = SPIFFS.open("/tmp.txt", "w");
+    if (!tmp) {
+      fail("failed to re-open empty file");
+    }
+  }
   Serial.println("success");
 }