refactor: what a double-click on a node opens is a contribution point

CHANGELOG.md

@@ -63,6 +63,14 @@ version check rather than run against what it no longer has.
 
 ### Added
 
+- **What a double-click on a node opens is a contribution point:
+  `NodeOpener`** (exported). An opener answers before the platform's own
+  definition navigation, or leaves the node to it; one per `id`, the last
+  binding winning. The `@viewer` half of the double-click listener (open,
+  diff, open with an editor or run a command on a task's last tokens, or a
+  path it declares) is the `viewer` opener (`viewer-node-opener.ts`), which
+  the stock module binds until wfpy-ide binds its own.
+
 - **What a product's webview code needs, from the package.**
   `@dialogram/diagram-client` exports `VscodeUi` (the host's quick picks,
   input boxes and commands), `clientBehavior`, `commandId`, `offersRun`,

packages/diagram-client/README.md

@@ -272,6 +272,15 @@ bundle is an example of all three: its `src/webview/agent-ui/` holds the
 `@tool` and `@agent` editors, the agent sections (Basic Info's Skill row,
 Agent Tools, the live Agent Context) and the `@tool` and `@viewer` templates.
 
+**Node openers.** A double-click on a node opens its definition, unless the
+network navigation opens something for it. To open something else for some
+of your nodes, bind a `NodeOpener` with an `id`: its `open(node, { sourceUri })`
+returns the actions to run, or `undefined` to leave the node to the platform.
+Openers are asked in the order their ids were first bound, and the first
+that answers wins; a later binding for an id replaces the earlier one. The
+stock bundle binds wfpy's `@viewer` opener (id `viewer`) until wfpy-ide binds
+its own.
+
 **A diagram of your own.** When you compose the container yourself:
 
 ```ts

packages/diagram-client/src/index.ts

@@ -78,6 +78,7 @@ export {
     type PanelModelRoot
 } from './node-section';
 export { createPropertySection, escapeHtml, shortenPath } from './property-section';
+export { NodeOpener, type NodeOpenerContext } from './node-opener';
 export {
     AnnotationTemplate,
     CUSTOM_ANNOTATION_ENTRY,

packages/diagram-client/src/node-opener.ts

@@ -0,0 +1,37 @@
+/**
+ * Node openers: the contribution point for what a double-click on a node
+ * opens.
+ *
+ * The platform opens a node's definition (preview), unless the network
+ * navigation listener already opens something for it. An opener a product
+ * binds is asked first: it answers with the actions that open what the node
+ * stands for in that product, or `undefined` to leave the node to the
+ * platform. A product binds its openers in a feature module:
+ *
+ *     bind(NodeOpener).toConstantValue(myOpener);
+ *
+ * There is one opener per `id`: a later binding for an id replaces the
+ * earlier one, and an opener without an id is dropped. Openers are asked in
+ * the order their ids were first bound; the first that answers with actions
+ * wins (an empty list is no answer), and one that throws is skipped.
+ *
+ * The network navigation listener may open something for the same
+ * double-click (a node's first view); the platform's definition stands back
+ * for it, but an opener's answer does not. An opener should leave such nodes
+ * unless it means to open its own thing beside the view.
+ */
+import type { Action, GModelElement } from '@eclipse-glsp/sprotty';
+
+export const NodeOpener = Symbol.for('dialogram.NodeOpener');
+
+export interface NodeOpenerContext {
+    /** The file the diagram was opened from, if any. */
+    readonly sourceUri: string | undefined;
+}
+
+export interface NodeOpener {
+    /** What the opener is, for a later binding to replace it. */
+    readonly id: string;
+    /** The actions a double-click on `node` runs, or `undefined` (or none) to leave it to the platform. */
+    open(node: GModelElement, context: NodeOpenerContext): Array<Action | Promise<Action>> | undefined;
+}

packages/diagram-client/src/stock-features.module.ts

@@ -18,6 +18,8 @@ import { clientBehavior } from './profile';
 import { WorkflowNavigationUi } from './navigation-ui';
 import { WorkflowNetworkNavigationMouseListener } from './network-navigation-mouse-listener';
 import { ViewerMouseListener } from './viewer-mouse-listener';
+import { NodeOpener } from './node-opener';
+import { ViewerNodeOpener } from './viewer-node-opener';
 import { EdgeOpenMouseListener } from './edge-open-mouse-listener';
 import { WhitespaceRootPropertiesMouseListener } from './whitespace-root-properties-mouse-listener';
 import { WorkflowElkLiveDragRouter } from './elk-live-drag-router';
@@ -111,8 +113,12 @@ export const workflowFeaturesModule = new ContainerModule((bind, unbind, isBound
     // Double-click navigation into nested networks.
     bindAsService(context, TYPES.MouseListener, WorkflowNetworkNavigationMouseListener);
 
-    // Double-click on @viewer external tasks to open/diff the last token files.
+    // Double-click on a node: what a product's openers open for it, else its
+    // definition (every product relies on the latter).
     bindAsService(context, TYPES.MouseListener, ViewerMouseListener);
+    // What a double-click on a `@viewer` task opens (its last tokens), until
+    // the product that has `@viewer` binds it in its own bundle.
+    bind(NodeOpener).toConstantValue(new ViewerNodeOpener());
 
     // Double-click on diagram whitespace to show root/workflow properties.
     bindAsService(context, TYPES.MouseListener, WhitespaceRootPropertiesMouseListener);