feat(base): add guard to method nth of component (#181)

Author: clebert

@pageobject/base/src/Component.test.ts

@@ -79,7 +79,7 @@ function describeExistingVariants<TComponent extends TestComponent>(
 
   return [
     new Descriptor(
-      component.nth(position + 1).nth(position),
+      component.nth(position),
       `.nth(${position})`,
       parentDescriptor,
       position
@@ -213,6 +213,12 @@ function describeTests<TComponent extends TestComponent>(
             'Position must be one-based'
           );
         });
+
+        it('should throw a state error', () => {
+          expect(() => descriptor.component.nth(1).nth(2)).toThrow(
+            'Position is already set'
+          );
+        });
       });
 
       describe('getElementCount() => Effect', () => {

@pageobject/base/src/Component.ts

@@ -68,6 +68,10 @@ export class Component<TElement> implements Describable {
       throw new Error('Position must be one-based');
     }
 
+    if (this._locator.position) {
+      throw new Error('Position is already set');
+    }
+
     return this._ownFactory.create(this._adapter, {...this._locator, position});
   }
 

docs/api/base/classes/component.html

@@ -1131,7 +1131,7 @@ <h3><span class="tsd-flag ts-flagProtected">Protected</span> find<wbr>Element</h
 					<li class="tsd-description">
 						<aside class="tsd-sources">
 							<ul>
-								<li>Defined in <a href="https://github.com/clebert/pageobject/blob/master/@pageobject/base/src/Component.ts#L92">Component.ts:92</a></li>
+								<li>Defined in <a href="https://github.com/clebert/pageobject/blob/master/@pageobject/base/src/Component.ts#L96">Component.ts:96</a></li>
 							</ul>
 						</aside>
 						<h4 class="tsd-returns-title">Returns <span class="tsd-signature-type">Promise</span><span class="tsd-signature-symbol">&lt;</span><span class="tsd-signature-type">TElement</span><span class="tsd-signature-symbol">&gt;</span></h4>
@@ -1148,7 +1148,7 @@ <h3><span class="tsd-flag ts-flagProtected">Protected</span> find<wbr>Elements</
 					<li class="tsd-description">
 						<aside class="tsd-sources">
 							<ul>
-								<li>Defined in <a href="https://github.com/clebert/pageobject/blob/master/@pageobject/base/src/Component.ts#L106">Component.ts:106</a></li>
+								<li>Defined in <a href="https://github.com/clebert/pageobject/blob/master/@pageobject/base/src/Component.ts#L110">Component.ts:110</a></li>
 							</ul>
 						</aside>
 						<h4 class="tsd-returns-title">Returns <span class="tsd-signature-type">Promise</span><span class="tsd-signature-symbol">&lt;</span><span class="tsd-signature-type">TElement</span><span class="tsd-signature-symbol">[]</span><span class="tsd-signature-symbol">&gt;</span></h4>
@@ -1165,7 +1165,7 @@ <h3>get<wbr>Element<wbr>Count</h3>
 					<li class="tsd-description">
 						<aside class="tsd-sources">
 							<ul>
-								<li>Defined in <a href="https://github.com/clebert/pageobject/blob/master/@pageobject/base/src/Component.ts#L86">Component.ts:86</a></li>
+								<li>Defined in <a href="https://github.com/clebert/pageobject/blob/master/@pageobject/base/src/Component.ts#L90">Component.ts:90</a></li>
 							</ul>
 						</aside>
 						<h4 class="tsd-returns-title">Returns <a href="../interfaces/effect.html" class="tsd-signature-type">Effect</a><span class="tsd-signature-symbol">&lt;</span><span class="tsd-signature-type">number</span><span class="tsd-signature-symbol">&gt;</span></h4>
@@ -1234,7 +1234,7 @@ <h3>where</h3>
 					<li class="tsd-description">
 						<aside class="tsd-sources">
 							<ul>
-								<li>Defined in <a href="https://github.com/clebert/pageobject/blob/master/@pageobject/base/src/Component.ts#L74">Component.ts:74</a></li>
+								<li>Defined in <a href="https://github.com/clebert/pageobject/blob/master/@pageobject/base/src/Component.ts#L78">Component.ts:78</a></li>
 							</ul>
 						</aside>
 						<h4 class="tsd-type-parameters-title">Type parameters</h4>