JavaScript Plugin API, providing custom panels and column menu items

Thanks, Cameron Yick.

https://github.com/simonw/datasette/pull/2052

Co-authored-by: Simon Willison <swillison@gmail.com>

datasette/static/datasette-manager.js

@@ -0,0 +1,210 @@
+// Custom events for use with the native CustomEvent API
+const DATASETTE_EVENTS = {
+  INIT: "datasette_init", // returns datasette manager instance in evt.detail
+};
+
+// Datasette "core" -> Methods/APIs that are foundational
+// Plugins will have greater stability if they use the functional hooks- but if they do decide to hook into
+// literal DOM selectors, they'll have an easier time using these addresses.
+const DOM_SELECTORS = {
+  /** Should have one match */
+  jsonExportLink: ".export-links a[href*=json]",
+
+  /** Event listeners that go outside of the main table, e.g. existing scroll listener */
+  tableWrapper: ".table-wrapper",
+  table: "table.rows-and-columns",
+  aboveTablePanel: ".above-table-panel",
+
+  // These could have multiple matches
+  /** Used for selecting table headers. Use makeColumnActions if you want to add menu items. */
+  tableHeaders: `table.rows-and-columns th`,
+
+  /** Used to add "where"  clauses to query using direct manipulation */
+  filterRows: ".filter-row",
+  /** Used to show top available enum values for a column ("facets") */
+  facetResults: ".facet-results [data-column]",
+};
+
+/**
+ * Monolith class for interacting with Datasette JS API
+ * Imported with DEFER, runs after main document parsed
+ * For now, manually synced with datasette/version.py
+ */
+const datasetteManager = {
+  VERSION: window.datasetteVersion,
+
+  // TODO: Should order of registration matter more?
+
+  // Should plugins be allowed to clobber others or is it last-in takes priority?
+  // Does pluginMetadata need to be serializable, or can we let it be stateful / have functions?
+  plugins: new Map(),
+
+  registerPlugin: (name, pluginMetadata) => {
+    if (datasetteManager.plugins.has(name)) {
+      console.warn(`Warning -> plugin ${name} was redefined`);
+    }
+    datasetteManager.plugins.set(name, pluginMetadata);
+
+    // If the plugin participates in the panel... update the panel.
+    if (pluginMetadata.makeAboveTablePanelConfigs) {
+      datasetteManager.renderAboveTablePanel();
+    }
+  },
+
+  /**
+   * New DOM elements are created on each click, so the data is not stale.
+   *
+   * Items
+   *  - must provide label (text)
+   *  - might provide href (string) or an onclick ((evt) => void)
+   *
+   * columnMeta is metadata stored on the column header (TH) as a DOMStringMap
+   * - column: string
+   * - columnNotNull: boolean
+   * - columnType: sqlite datatype enum (text, number, etc)
+   * - isPk: boolean
+   */
+  makeColumnActions: (columnMeta) => {
+    let columnActions = [];
+
+    // Accept function that returns list of columnActions with keys
+    // Required: label (text)
+    // Optional: onClick or href
+    datasetteManager.plugins.forEach((plugin) => {
+      if (plugin.makeColumnActions) {
+        // Plugins can provide multiple columnActions if they want
+        // If multiple try to create entry with same label, the last one deletes the others
+        columnActions.push(...plugin.makeColumnActions(columnMeta));
+      }
+    });
+
+    // TODO: Validate columnAction configs and give informative error message if missing keys.
+    return columnActions;
+  },
+
+  /**
+   * In MVP, each plugin can only have 1 instance.
+   * In future, panels could be repeated. We omit that for now since so many plugins depend on
+   * shared URL state, so having multiple instances of plugin at same time is problematic.
+   * Currently, we never destroy any panels, we just hide them.
+   *
+   * TODO: nicer panel css, show panel selection state.
+   * TODO: does this hook need to take any arguments?
+   */
+  renderAboveTablePanel: () => {
+    const aboveTablePanel = document.querySelector(
+      DOM_SELECTORS.aboveTablePanel
+    );
+
+    if (!aboveTablePanel) {
+      console.warn(
+        "This page does not have a table, the renderAboveTablePanel cannot be used."
+      );
+      return;
+    }
+
+    let aboveTablePanelWrapper = aboveTablePanel.querySelector(".panels");
+
+    // First render: create wrappers. Otherwise, reuse previous.
+    if (!aboveTablePanelWrapper) {
+      aboveTablePanelWrapper = document.createElement("div");
+      aboveTablePanelWrapper.classList.add("tab-contents");
+      const panelNav = document.createElement("div");
+      panelNav.classList.add("tab-controls");
+
+      // Temporary: css for minimal amount of breathing room.
+      panelNav.style.display = "flex";
+      panelNav.style.gap = "8px";
+      panelNav.style.marginTop = "4px";
+      panelNav.style.marginBottom = "20px";
+
+      aboveTablePanel.appendChild(panelNav);
+      aboveTablePanel.appendChild(aboveTablePanelWrapper);
+    }
+
+    datasetteManager.plugins.forEach((plugin, pluginName) => {
+      const { makeAboveTablePanelConfigs } = plugin;
+
+      if (makeAboveTablePanelConfigs) {
+        const controls = aboveTablePanel.querySelector(".tab-controls");
+        const contents = aboveTablePanel.querySelector(".tab-contents");
+
+        // Each plugin can make multiple panels
+        const configs = makeAboveTablePanelConfigs();
+
+        configs.forEach((config, i) => {
+          const nodeContentId = `${pluginName}_${config.id}_panel-content`;
+
+          // quit if we've already registered this plugin
+          // TODO: look into whether plugins should be allowed to ask
+          // parent to re-render, or if they should manage that internally.
+          if (document.getElementById(nodeContentId)) {
+            return;
+          }
+
+          // Add tab control button
+          const pluginControl = document.createElement("button");
+          pluginControl.textContent = config.label;
+          pluginControl.onclick = () => {
+            contents.childNodes.forEach((node) => {
+              if (node.id === nodeContentId) {
+                node.style.display = "block";
+              } else {
+                node.style.display = "none";
+              }
+            });
+          };
+          controls.appendChild(pluginControl);
+
+          // Add plugin content area
+          const pluginNode = document.createElement("div");
+          pluginNode.id = nodeContentId;
+          config.render(pluginNode);
+          pluginNode.style.display = "none"; // Default to hidden unless you're ifrst
+
+          contents.appendChild(pluginNode);
+        });
+
+        // Let first node be selected by default
+        if (contents.childNodes.length) {
+          contents.childNodes[0].style.display = "block";
+        }
+      }
+    });
+  },
+
+  /** Selectors for document (DOM) elements. Store identifier instead of immediate references in case they haven't loaded when Manager starts. */
+  selectors: DOM_SELECTORS,
+
+  // Future API ideas
+  // Fetch page's data in array, and cache so plugins could reuse it
+  // Provide knowledge of what datasette JS or server-side via traditional console autocomplete
+  // State helpers: URL params https://github.com/simonw/datasette/issues/1144 and localstorage
+  // UI Hooks: command + k, tab manager hook
+  // Should we notify plugins that have dependencies
+  // when all dependencies were fulfilled? (leaflet, codemirror, etc)
+  // https://github.com/simonw/datasette-leaflet -> this way
+  // multiple plugins can all request the same copy of leaflet.
+};
+
+const initializeDatasette = () => {
+  // Hide the global behind __ prefix. Ideally they should be listening for the
+  // DATASETTE_EVENTS.INIT event to avoid the habit of reading from the window.
+
+  window.__DATASETTE__ = datasetteManager;
+  console.debug("Datasette Manager Created!");
+
+  const initDatasetteEvent = new CustomEvent(DATASETTE_EVENTS.INIT, {
+    detail: datasetteManager,
+  });
+
+  document.dispatchEvent(initDatasetteEvent);
+};
+
+/**
+ * Main function
+ * Fires AFTER the document has been parsed
+ */
+document.addEventListener("DOMContentLoaded", function () {
+  initializeDatasette();
+});

datasette/static/table.js

@@ -17,7 +17,8 @@ var DROPDOWN_ICON_SVG = `<svg xmlns="http://www.w3.org/2000/svg" width="14" heig
   <path d="M19.4 15a1.65 1.65 0 0 0 .33 1.82l.06.06a2 2 0 0 1 0 2.83 2 2 0 0 1-2.83 0l-.06-.06a1.65 1.65 0 0 0-1.82-.33 1.65 1.65 0 0 0-1 1.51V21a2 2 0 0 1-2 2 2 2 0 0 1-2-2v-.09A1.65 1.65 0 0 0 9 19.4a1.65 1.65 0 0 0-1.82.33l-.06.06a2 2 0 0 1-2.83 0 2 2 0 0 1 0-2.83l.06-.06a1.65 1.65 0 0 0 .33-1.82 1.65 1.65 0 0 0-1.51-1H3a2 2 0 0 1-2-2 2 2 0 0 1 2-2h.09A1.65 1.65 0 0 0 4.6 9a1.65 1.65 0 0 0-.33-1.82l-.06-.06a2 2 0 0 1 0-2.83 2 2 0 0 1 2.83 0l.06.06a1.65 1.65 0 0 0 1.82.33H9a1.65 1.65 0 0 0 1-1.51V3a2 2 0 0 1 2-2 2 2 0 0 1 2 2v.09a1.65 1.65 0 0 0 1 1.51 1.65 1.65 0 0 0 1.82-.33l.06-.06a2 2 0 0 1 2.83 0 2 2 0 0 1 0 2.83l-.06.06a1.65 1.65 0 0 0-.33 1.82V9a1.65 1.65 0 0 0 1.51 1H21a2 2 0 0 1 2 2 2 2 0 0 1-2 2h-.09a1.65 1.65 0 0 0-1.51 1z"></path>
 </svg>`;
 
-(function () {
+/** Main initialization function for Datasette Table interactions */
+const initDatasetteTable = function (manager) {
   // Feature detection
   if (!window.URLSearchParams) {
     return;
@@ -68,13 +69,11 @@ var DROPDOWN_ICON_SVG = `<svg xmlns="http://www.w3.org/2000/svg" width="14" heig
     menu.style.display = "none";
     menu.classList.remove("anim-scale-in");
   }
-  // When page loads, add scroll listener on .table-wrapper
-  document.addEventListener("DOMContentLoaded", () => {
-    var tableWrapper = document.querySelector(".table-wrapper");
-    if (tableWrapper) {
-      tableWrapper.addEventListener("scroll", closeMenu);
-    }
-  });
+
+  const tableWrapper = document.querySelector(manager.selectors.tableWrapper);
+  if (tableWrapper) {
+    tableWrapper.addEventListener("scroll", closeMenu);
+  }
   document.body.addEventListener("click", (ev) => {
     /* was this click outside the menu? */
     var target = ev.target;
@@ -85,7 +84,8 @@ var DROPDOWN_ICON_SVG = `<svg xmlns="http://www.w3.org/2000/svg" width="14" heig
       closeMenu();
     }
   });
-  function iconClicked(ev) {
+
+  function onTableHeaderClick(ev) {
     ev.preventDefault();
     ev.stopPropagation();
     var th = ev.target;
@@ -185,7 +185,40 @@ var DROPDOWN_ICON_SVG = `<svg xmlns="http://www.w3.org/2000/svg" width="14" heig
     menu.style.left = menuLeft + "px";
     menu.style.display = "block";
     menu.classList.add("anim-scale-in");
+
+    // Custom menu items on each render
+    // Plugin hook: allow adding JS-based additional menu items
+    const columnActionsPayload = {
+      columnName: th.dataset.column,
+      columnNotNull: th.dataset.columnNotNull === '1',
+      columnType: th.dataset.columnType,
+      isPk: th.dataset.isPk === '1'
+    };
+    const columnItemConfigs = manager.makeColumnActions(columnActionsPayload);
+
+    const menuList = menu.querySelector('ul');
+    columnItemConfigs.forEach(itemConfig => {
+      // Remove items from previous render. We assume entries have unique labels.
+      const existingItems = menuList.querySelectorAll(`li`);
+      Array.from(existingItems).filter(item => item.innerText === itemConfig.label).forEach(node => {
+        node.remove();
+      });
+
+      const newLink = document.createElement('a');
+      newLink.textContent = itemConfig.label;
+      newLink.href = itemConfig.href ?? '#';
+      if (itemConfig.onClick) {
+        newLink.onclick = itemConfig.onClick;
+      }
+
+      // Attach new elements to DOM
+      const menuItem = document.createElement('li');
+      menuItem.appendChild(newLink);
+      menuList.appendChild(menuItem);
+    });
+
   }
+
   var svg = document.createElement("div");
   svg.innerHTML = DROPDOWN_ICON_SVG;
   svg = svg.querySelector("*");
@@ -197,21 +230,21 @@ var DROPDOWN_ICON_SVG = `<svg xmlns="http://www.w3.org/2000/svg" width="14" heig
   menu.style.display = "none";
   document.body.appendChild(menu);
 
-  var ths = Array.from(document.querySelectorAll(".rows-and-columns th"));
+  var ths = Array.from(document.querySelectorAll(manager.selectors.tableHeaders));
   ths.forEach((th) => {
     if (!th.querySelector("a")) {
       return;
     }
     var icon = svg.cloneNode(true);
-    icon.addEventListener("click", iconClicked);
+    icon.addEventListener("click", onTableHeaderClick);
     th.appendChild(icon);
   });
-})();
+};
 
 /* Add x buttons to the filter rows */
-(function () {
+function addButtonsToFilterRows(manager) {
   var x = "✖";
-  var rows = Array.from(document.querySelectorAll(".filter-row")).filter((el) =>
+  var rows = Array.from(document.querySelectorAll(manager.selectors.filterRow)).filter((el) =>
     el.querySelector(".filter-op")
   );
   rows.forEach((row) => {
@@ -234,13 +267,13 @@ var DROPDOWN_ICON_SVG = `<svg xmlns="http://www.w3.org/2000/svg" width="14" heig
       a.style.display = "none";
     }
   });
-})();
+};
 
 /* Set up datalist autocomplete for filter values */
-(function () {
+function initAutocompleteForFilterValues(manager) {
   function createDataLists() {
     var facetResults = document.querySelectorAll(
-      ".facet-results [data-column]"
+      manager.selectors.facetResults
     );
     Array.from(facetResults).forEach(function (facetResult) {
       // Use link text from all links in the facet result
@@ -266,9 +299,21 @@ var DROPDOWN_ICON_SVG = `<svg xmlns="http://www.w3.org/2000/svg" width="14" heig
   document.body.addEventListener("change", function (event) {
     if (event.target.name === "_filter_column") {
       event.target
-        .closest(".filter-row")
+        .closest(manager.selectors.filterRow)
         .querySelector(".filter-value")
         .setAttribute("list", "datalist-" + event.target.value);
     }
   });
-})();
+};
+
+// Ensures Table UI is initialized only after the Manager is ready.
+document.addEventListener("datasette_init", function (evt) {
+  const { detail: manager } = evt;
+
+  // Main table
+  initDatasetteTable(manager);
+
+  // Other UI functions with interactive JS needs
+  addButtonsToFilterRows(manager);
+  initAutocompleteForFilterValues(manager);
+});

datasette/templates/_table.html

@@ -1,3 +1,5 @@
+<!-- above-table-panel is a hook node for plugins to attach to . Displays even if no data available -->
+<div class="above-table-panel"> </div>
 {% if display_rows %}
 <div class="table-wrapper">
     <table class="rows-and-columns">

datasette/templates/base.html

@@ -7,6 +7,8 @@
 {% for url in extra_css_urls %}
     <link rel="stylesheet" href="{{ url.url }}"{% if url.get("sri") %} integrity="{{ url.sri }}" crossorigin="anonymous"{% endif %}>
 {% endfor %}
+<script>window.datasetteVersion = '{{ datasette_version }}';</script>
+<script src="{{ urls.static('datasette-manager.js') }}" defer></script>
 {% for url in extra_js_urls %}
     <script {% if url.module %}type="module" {% endif %}src="{{ url.url }}"{% if url.get("sri") %} integrity="{{ url.sri }}" crossorigin="anonymous"{% endif %}></script>
 {% endfor %}

demos/plugins/example_js_manager_plugins.py

@@ -0,0 +1,21 @@
+from datasette import hookimpl
+
+# Test command:
+# datasette fixtures.db \ --plugins-dir=demos/plugins/
+#                       \ --static static:demos/plugins/static
+
+# Create a set with view names that qualify for this JS, since plugins won't do anything on other pages
+# Same pattern as in Nteract data explorer
+# https://github.com/hydrosquall/datasette-nteract-data-explorer/blob/main/datasette_nteract_data_explorer/__init__.py#L77
+PERMITTED_VIEWS = {"table", "query", "database"}
+
+
+@hookimpl
+def extra_js_urls(view_name):
+    print(view_name)
+    if view_name in PERMITTED_VIEWS:
+        return [
+            {
+                "url": f"/static/table-example-plugins.js",
+            }
+        ]

demos/plugins/static/table-example-plugins.js

@@ -0,0 +1,100 @@
+/**
+ * Example usage of Datasette JS Manager API
+ */
+
+document.addEventListener("datasette_init", function (evt) {
+  const { detail: manager } = evt;
+  // === Demo plugins: remove before merge===
+  addPlugins(manager);
+});
+
+/**
+ * Examples for to test datasette JS api
+ */
+const addPlugins = (manager) => {
+
+  manager.registerPlugin("column-name-plugin", {
+    version: 0.1,
+    makeColumnActions: (columnMeta) => {
+      const { column } = columnMeta;
+
+      return [
+        {
+          label: "Copy name to clipboard",
+          onClick: (evt) => copyToClipboard(column),
+        },
+        {
+          label: "Log column metadata to console",
+          onClick: (evt) => console.log(column),
+        },
+      ];
+    },
+  });
+
+  manager.registerPlugin("panel-plugin-graphs", {
+    version: 0.1,
+    makeAboveTablePanelConfigs: () => {
+      return [
+        {
+          id: 'first-panel',
+          label: "First",
+          render: node => {
+            const description = document.createElement('p');
+            description.innerText = 'Hello world';
+            node.appendChild(description);
+          }
+        },
+        {
+          id: 'second-panel',
+          label: "Second",
+          render: node => {
+            const iframe = document.createElement('iframe');
+            iframe.src = "https://observablehq.com/embed/@d3/sortable-bar-chart?cell=viewof+order&cell=chart";
+            iframe.width = 800;
+            iframe.height = 635;
+            iframe.frameborder = '0';
+            node.appendChild(iframe);
+          }
+        },
+      ];
+    },
+  });
+
+  manager.registerPlugin("panel-plugin-maps", {
+    version: 0.1,
+    makeAboveTablePanelConfigs: () => {
+      return [
+        {
+          // ID only has to be unique within a plugin, manager namespaces for you
+          id: 'first-map-panel',
+          label: "Map plugin",
+          // datasette-vega, leafleft can provide a "render" function
+          render: node => node.innerHTML = "Here sits a map",
+        },
+        {
+          id: 'second-panel',
+          label: "Image plugin",
+          render: node => {
+            const img = document.createElement('img');
+            img.src = 'https://datasette.io/static/datasette-logo.svg'
+            node.appendChild(img);
+          },
+        }
+      ];
+    },
+  });
+
+  // Future: dispatch message to some other part of the page with CustomEvent API
+  // Could use to drive filter/sort query builder actions without  page refresh.
+}
+
+
+
+async function copyToClipboard(str) {
+  try {
+    await navigator.clipboard.writeText(str);
+  } catch (err) {
+    /** Rejected - text failed to copy to the clipboard. Browsers didn't give permission */
+    console.error('Failed to copy: ', err);
+  }
+}