fix(area): Fix unnecessary area element generation

Make sure area element to be generated only for area types.

Fix #2826

src/ChartInternal/shape/line.ts

@@ -45,7 +45,11 @@ export default {
 
 		// Areas
 		if ($$.hasTypeOf("Area")) {
-			$$.initArea(!area && mainLineEnter.empty() ? mainLineUpdate : mainLineEnter);
+			const mainLine = (
+				!area && mainLineEnter.empty() ? mainLineUpdate : mainLineEnter
+			).filter($$.isAreaType.bind($$));
+
+			$$.initArea(mainLine);
 		}
 
 		$$.updateTargetForCircle(targets, mainLineEnter);

test/shape/area-spec.ts

@@ -97,7 +97,6 @@ describe("SHAPE AREA", () => {
 			});
 		}
 
-
 		it("check bar path node position: non rotated Axis", () => {
 			checkBarPathPos("y");
 		});
@@ -109,6 +108,31 @@ describe("SHAPE AREA", () => {
 		it("check bar path node position: rotated Axis", () => {
 			checkBarPathPos("x");
 		});
+
+		it("set options", () => {
+			args = {
+				data: {
+					columns: [
+						["data1", 800, 750, 730],
+						["data2", null, 500, 730]
+					],
+					type: "line",
+					types: {
+						data1: "area"
+					}
+				}
+			};
+		});
+
+		it("area element should be generated for area type dataset only.", () => {
+			const {areas} = chart.$.line;
+
+			expect(areas.size()).to.be.equal(1);
+
+			areas.each(function() {
+				expect(/undefined/.test(this.getAttribute("d"))).to.be.false;
+			});
+		});
 	});
 
 	describe("area-range type generation", () => {