Fix option ingredients being overwriten

src/web/HTMLIngredient.mjs

@@ -166,6 +166,7 @@ class HTMLIngredient {
                         id="${this.id}"
                         tabindex="${this.tabIndex}"
                         arg-name="${this.name}"
+                        data-target="${this.target}"
                         ${this.disabled ? "disabled" : ""}>`;
                 for (i = 0; i < this.value.length; i++) {
                     if ((m = this.value[i].name.match(/\[([a-z0-9 -()^]+)\]/i))) {

src/web/waiters/RecipeWaiter.mjs

@@ -487,11 +487,19 @@ class RecipeWaiter {
      * @param {HTMLElement} op
      */
     triggerArgEvents(op) {
-        // Trigger populateOption and argSelector events
+        // Trigger argSelector events and populateOption events only where the target is empty.
+        // When loading a saved recipe, arguments are populated before this method is called, so
+        // re-triggering populateOption events would overwrite saved custom values with defaults.
+        const args = op.querySelectorAll(".arg");
         const triggerableOptions = op.querySelectorAll(".populate-option, .arg-selector");
         const evt = new Event("change", {bubbles: true});
+
         if (triggerableOptions.length) {
             for (const el of triggerableOptions) {
+                if (el.classList.contains("populate-option")) {
+                    const target = args[el.getAttribute("data-target")];
+                    if (target && target.value !== "") continue;
+                }
                 el.dispatchEvent(evt);
             }
         }

tests/browser/03_recipe_load.js

@@ -0,0 +1,48 @@
+/**
+ * Regression tests for recipe loading behaviour.
+ *
+ * @author C85297 [95289555+C85297@users.noreply.github.com]
+ * @copyright Crown Copyright
+ * @license Apache-2.0
+ */
+
+const utils = require("./browserUtils.js");
+
+module.exports = {
+    before: browser => {
+        browser
+            .resizeWindow(1280, 800)
+            .url(browser.launchUrl)
+            .useCss()
+            .waitForElementNotPresent("#preloader", 10000);
+    },
+
+    "Recipe load preserves populated arguments": browser => {
+        const inputFormat = "HH:mm:ss a MMM DD, YYYY ";
+        const input = "10:20:30 pm Sep 26, 2019 ";
+
+        utils.loadRecipe(
+            browser,
+            "Translate DateTime Format",
+            input,
+            [
+                "Standard date and time",
+                inputFormat,
+                "UTC",
+                "DD/MM/YYYY HH:mm:ss",
+                "UTC"
+            ]
+        );
+
+        browser.execute(() => {
+            return Array.from(document.querySelectorAll("#rec-list li.operation .arg"))
+                .map(arg => arg.value);
+        }, [], function({value}) {
+            browser.expect(value[1]).to.equal(inputFormat);
+        });
+    },
+
+    after: browser => {
+        browser.end();
+    }
+};