fix: clean up plugin setup script tags (#7750)

* fix: clean up plugin setup script tags

Remove temporary plugin setup script elements from document.head after load

or load failure so repeated plugin loads do not leave stale DOM nodes

behind.

Related to #7388

* test: verify plugin setup script execution

Author: rish106-hub

js/utils/__tests__/utils-plugin-loader.test.js

@@ -0,0 +1,148 @@
+// Copyright (c) 2026 Music Blocks contributors
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the The GNU Affero General Public
+// License as published by the Free Software Foundation; either
+// version 3 of the License, or (at your option) any later version.
+//
+// You should have received a copy of the GNU Affero General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, 51 Franklin Street, Suite 500 Boston, MA 02110-1335 USA
+
+const createActivity = () => ({
+    blocks: {
+        protoBlockDict: {}
+    },
+    logo: {
+        evalFlowDict: {},
+        evalArgDict: {},
+        evalSetterDict: {},
+        evalParameterDict: {},
+        evalOnStartList: {},
+        evalOnStopList: {}
+    },
+    palettes: {
+        buttons: {},
+        add: jest.fn(),
+        makePalettes: jest.fn(),
+        updatePalettes: jest.fn(),
+        show: jest.fn(),
+        pluginMacros: {}
+    },
+    pluginsImages: {}
+});
+
+describe("processPluginData script cleanup", () => {
+    let processPluginData;
+    let originalCreateObjectURL;
+    let originalRevokeObjectURL;
+    let originalBlob;
+    let appendChildSpy;
+    let blobUrls;
+    let blobUrlIndex;
+
+    beforeEach(() => {
+        jest.useFakeTimers();
+        jest.resetModules();
+        document.head.innerHTML = "";
+
+        global._ = msg => msg;
+        global.PALETTEICONS = {};
+        global.PALETTEFILLCOLORS = {};
+        global.PALETTESTROKECOLORS = {};
+        global.PALETTEHIGHLIGHTCOLORS = {};
+        global.HIGHLIGHTSTROKECOLORS = {};
+        global.MULTIPALETTES = [[], [], []];
+        global.platformColor = { paletteColors: {} };
+        window.__mb_plugin_registry = {};
+
+        originalCreateObjectURL = URL.createObjectURL;
+        originalRevokeObjectURL = URL.revokeObjectURL;
+        originalBlob = global.Blob;
+        global.Blob = class {
+            constructor(parts) {
+                this.parts = parts;
+            }
+
+            text() {
+                return Promise.resolve(this.parts.join(""));
+            }
+        };
+        blobUrls = new Map();
+        blobUrlIndex = 0;
+        URL.createObjectURL = jest.fn(blob => {
+            const url = `blob:plugin-setup-${blobUrlIndex}`;
+            blobUrlIndex += 1;
+            blobUrls.set(url, blob);
+            return url;
+        });
+        URL.revokeObjectURL = jest.fn();
+
+        ({ processPluginData } = require("../utils.js"));
+    });
+
+    afterEach(() => {
+        if (appendChildSpy) {
+            appendChildSpy.mockRestore();
+            appendChildSpy = undefined;
+        }
+        URL.createObjectURL = originalCreateObjectURL;
+        URL.revokeObjectURL = originalRevokeObjectURL;
+        global.Blob = originalBlob;
+        document.head.innerHTML = "";
+        delete window.__mb_plugin_registry;
+        delete globalThis.pluginSetupLoaded;
+        jest.useRealTimers();
+    });
+
+    it("removes setup script elements after they load", async () => {
+        const originalAppendChild = document.head.appendChild.bind(document.head);
+        appendChildSpy = jest.spyOn(document.head, "appendChild").mockImplementation(script => {
+            originalAppendChild(script);
+            blobUrls
+                .get(script.src)
+                .text()
+                .then(code => {
+                    Function(code)();
+                    script.onload();
+                });
+            return script;
+        });
+
+        await processPluginData(
+            createActivity(),
+            JSON.stringify({
+                BLOCKPLUGINS: {
+                    testBlock: "globalThis.pluginSetupLoaded = true;"
+                }
+            }),
+            "plugins/test.json"
+        );
+
+        expect(globalThis.pluginSetupLoaded).toBe(true);
+        expect(document.head.querySelectorAll("script[src^='blob:plugin-setup']")).toHaveLength(0);
+        expect(URL.revokeObjectURL).toHaveBeenCalledWith("blob:plugin-setup-0");
+    });
+
+    it("removes setup script elements after load errors", async () => {
+        const originalAppendChild = document.head.appendChild.bind(document.head);
+        appendChildSpy = jest.spyOn(document.head, "appendChild").mockImplementation(script => {
+            originalAppendChild(script);
+            script.onerror(new Error("load failed"));
+            return script;
+        });
+
+        await processPluginData(
+            createActivity(),
+            JSON.stringify({
+                BLOCKPLUGINS: {
+                    testBlock: "globalThis.pluginSetupLoaded = true;"
+                }
+            }),
+            "plugins/test.json"
+        );
+
+        expect(document.head.querySelectorAll("script[src^='blob:plugin-setup']")).toHaveLength(0);
+        expect(URL.revokeObjectURL).toHaveBeenCalledWith("blob:plugin-setup-0");
+    });
+});

js/utils/utils.js

@@ -43,7 +43,7 @@ if (typeof module !== "undefined" && module.exports) {
    docBySelector, docByTagName, doPublish, doStopVideoCam, doSVG,
    doUseCamera, format, getTextWidth, hideDOMLabel, httpGet, httpPost, HttpRequest,
    importMembers, isSVGEmpty, prepareMacroExports, preparePluginExports,
-   processMacroData, processRawPluginData, windowHeight, windowWidth,
+   processMacroData, processPluginData, processRawPluginData, windowHeight, windowWidth,
    fnBrowserDetect, waitForReadiness
 */
 
@@ -966,10 +966,16 @@ window.__mb_plugin_registry["${registryName}"] = function(activity, globalActivi
                     delete window.__mb_plugin_registry[registryName];
                 }
                 URL.revokeObjectURL(sUrl);
+                if (sScript.parentNode) {
+                    sScript.parentNode.removeChild(sScript);
+                }
                 resolve();
             };
             sScript.onerror = () => {
                 URL.revokeObjectURL(sUrl);
+                if (sScript.parentNode) {
+                    sScript.parentNode.removeChild(sScript);
+                }
                 resolve(); // Still resolve to let others run
             };
             document.head.appendChild(sScript);
@@ -1535,6 +1541,7 @@ if (typeof module !== "undefined" && module.exports) {
         doSVG,
         isSVGEmpty,
         prepareMacroExports,
+        processPluginData,
         processMacroData,
         hideDOMLabel,
         displayMsg