Add hooks to let other plugins extend the Tasks plugin.

src/Query/Query.ts

@@ -1,4 +1,5 @@
-import { LayoutOptions } from '../TaskLayout';
+import type { ExtendParserHook } from 'QueryRenderer';
+import { LayoutOptions } from '../LayoutOptions';
 import type { Task } from '../Task';
 import type { IQuery } from '../IQuery';
 import { getSettings } from '../Config/Settings';
@@ -50,7 +51,7 @@ export class Query implements IQuery {
 
     private readonly commentRegexp = /^#.*/;
 
-    constructor({ source }: { source: string }) {
+    constructor({ source, extensions = [] }: { source: string; extensions?: ExtendParserHook[] }) {
         this.source = source;
         source
             .split('\n')
@@ -81,6 +82,8 @@ export class Query implements IQuery {
                         break;
                     case this.parseFilter(line):
                         break;
+                    case this.parseExtensions(extensions, line):
+                        break;
                     default:
                         this._error = `do not understand query: ${line}`;
                 }
@@ -235,4 +238,16 @@ export class Query implements IQuery {
             this._error = 'do not understand query grouping';
         }
     }
+
+    private parseExtensions(extensions: ExtendParserHook[], line: string): boolean {
+        let found = false;
+        // Let plugins that implement the "extendParse" hook parse the given
+        // line
+        extensions.forEach((extendParser: ExtendParserHook) => {
+            if (extendParser(line, this.layoutOptions)) {
+                found = true;
+            }
+        });
+        return found;
+    }
 }

src/QueryRenderer.ts

@@ -7,6 +7,7 @@ import { replaceTaskWithTasks } from './File';
 import { Query } from './Query/Query';
 import type { GroupHeading } from './Query/GroupHeading';
 import { TaskModal } from './TaskModal';
+import { Task as TaskModel } from './Task';
 import type { TasksEvents } from './TasksEvents';
 import type { Task } from './Task';
 import { DateFallback } from './DateFallback';
@@ -37,6 +38,9 @@ export class QueryRenderer {
     }
 }
 
+export type ExtendTaskHook = (listItem: HTMLLIElement, task: Task, api: object) => void;
+export type ExtendParserHook = (line: string, layoutOptions: object) => boolean;
+
 class QueryRenderChild extends MarkdownRenderChild {
     private readonly app: App;
     private readonly events: TasksEvents;
@@ -48,6 +52,9 @@ class QueryRenderChild extends MarkdownRenderChild {
     private renderEventRef: EventRef | undefined;
     private queryReloadTimeout: NodeJS.Timeout | undefined;
 
+    private extendTask: ExtendTaskHook[];
+    private extendParser: ExtendParserHook[];
+
     constructor({
         app,
         events,
@@ -67,18 +74,34 @@ class QueryRenderChild extends MarkdownRenderChild {
         this.events = events;
         this.source = source;
         this.filePath = filePath;
+        this.extendTask = [];
+        this.extendParser = [];
+
+        // Cache which plugins implement our extension hooks
+        // @ts-ignore
+        Object.keys(this.app.plugins.plugins).forEach((name) => {
+            // @ts-ignore
+            const plugin = this.app.plugins.plugins[name];
+            if (plugin.extendTask) {
+                this.extendTask.push(plugin.extendTask);
+            }
+
+            if (plugin.extendParser) {
+                this.extendParser.push(plugin.extendParser);
+            }
+        });
 
         // The engine is chosen on the basis of the code block language. Currently
         // there is only the main engine for the plugin, this allows others to be
         // added later.
         switch (this.containerEl.className) {
             case 'block-language-tasks':
-                this.query = new Query({ source });
+                this.query = new Query({ source, extensions: this.extendParser });
                 this.queryType = 'tasks';
                 break;
 
             default:
-                this.query = new Query({ source });
+                this.query = new Query({ source, extensions: this.extendParser });
                 this.queryType = 'tasks';
                 break;
         }
@@ -119,7 +142,7 @@ class QueryRenderChild extends MarkdownRenderChild {
         const millisecondsToMidnight = midnight.getTime() - now.getTime();
 
         this.queryReloadTimeout = setTimeout(() => {
-            this.query = new Query({ source: this.source });
+            this.query = new Query({ source: this.source, extensions: this.extendParser });
             // Process the current cache state:
             this.events.triggerRequestCacheUpdate(this.render.bind(this));
             this.reloadQueryAtMidnight();
@@ -215,6 +238,16 @@ class QueryRenderChild extends MarkdownRenderChild {
                 this.addEditButton(listItem, task);
             }
 
+            // Let plugins that implement the "extendTask" hook extend the
+            // current task
+            this.extendTask.forEach((extendTask: ExtendTaskHook) =>
+                extendTask(listItem, task, {
+                    layoutOptions: this.query.layoutOptions,
+                    Task: TaskModel,
+                    replaceTaskWithTasks,
+                }),
+            );
+
             taskList.appendChild(listItem);
         }