Throw exception if no field is provided when calling toLineProtocol()

CHANGELOG.md

@@ -1,5 +1,7 @@
 ## 3.5.0 [unreleased]
 
+1. [#149](https://github.com/influxdata/influxdb-client-php/issues/149): Throw exception on empty field
+
 ## 3.4.0 [2023-07-28]
 
 ### Bug Fixes

src/InfluxDB2/Point.php

@@ -114,9 +114,10 @@ public function time($time, $precision = null): Point
         return $this;
     }
 
-    /** If there is no field then return null.
+    /** If there is no field then throw an exception.
      *
      * @return string representation of the point
+     * @throws \InvalidArgumentException when no field is provided
      */
     public function toLineProtocol()
     {
@@ -135,7 +136,7 @@ public function toLineProtocol()
         $fields = $this->appendFields();
 
         if ($this->isNullOrEmptyString($fields)) {
-            return null;
+            throw new \InvalidArgumentException("Failed to write Point: At least one field is required.");
         }
 
         $lineProtocol .= $fields;

tests/PointTest.php

@@ -6,6 +6,7 @@
 use DateTimeImmutable;
 use InfluxDB2\Model\WritePrecision;
 use InfluxDB2\Point;
+use InvalidArgumentException;
 use PHPUnit\Framework\TestCase;
 
 class PointTest extends TestCase
@@ -262,11 +263,13 @@ public function testWithoutTags()
 
     public function testWithoutFields()
     {
+        $this->expectException(\InvalidArgumentException::class);
+
         $point = Point::measurement('h2o')
             ->addTag('location', 'europe')
             ->time(123);
 
-        $this->assertNull($point->toLineProtocol());
+        $point->toLineProtocol();
     }
 
     public function testFromArrayWithoutName()