fix(textarea): calculate max-height based on empty state (fix #184)

Author: mario-aleo

packages/textarea/src/LionTextarea.js

@@ -65,13 +65,20 @@ export class LionTextarea extends ObserverMixin(LionInput) {
    * To support maxRows we need to set max-height of the textarea
    */
   setTextareaMaxHeight() {
+    const { value } = this.inputElement;
+    this.inputElement.value = '';
+    this.resizeTextarea();
+
     const cs = window.getComputedStyle(this.inputElement, null);
     const lineHeight = parseFloat(cs.lineHeight) || parseFloat(cs.height) / this.rows;
     const paddingOffset = parseFloat(cs.paddingTop) + parseFloat(cs.paddingBottom);
     const borderOffset = parseFloat(cs.borderTopWidth) + parseFloat(cs.borderBottomWidth);
     const offset = cs.boxSizing === 'border-box' ? paddingOffset + borderOffset : 0;
 
     this.inputElement.style.maxHeight = `${lineHeight * this.maxRows + offset}px`;
+
+    this.inputElement.value = value;
+    this.resizeTextarea();
   }
 
   static get styles() {

packages/textarea/test/lion-textarea.test.js

@@ -61,6 +61,31 @@ describe('<lion-textarea>', () => {
     }, Promise.resolve(0));
   });
 
+  it('stops growing after property "maxRows" is reached when there was an initial value', async () => {
+    const el = await fixture(
+      html`
+        <lion-textarea .modelValue="${'1\n2\n3'}"></lion-textarea>
+      `,
+    );
+
+    return [4, 5, 6, 7, 8].reduce(async (heightPromise, i) => {
+      const oldHeight = await heightPromise;
+      el.modelValue += `\n`;
+      await el.updateComplete;
+      const newHeight = el.offsetHeight;
+
+      if (i > el.maxRows) {
+        // stop growing
+        expect(newHeight).to.equal(oldHeight);
+      } else if (i > el.rows) {
+        // growing normally
+        expect(newHeight >= oldHeight).to.equal(true);
+      }
+
+      return Promise.resolve(newHeight);
+    }, Promise.resolve(0));
+  });
+
   it('stops shrinking after property "rows" is reached', async () => {
     const el = await fixture(
       html`