feat: implement reverse sorting of groups

Author: ilandikov

src/Query/Filter/Field.ts

@@ -342,8 +342,8 @@ export abstract class Field {
             return null;
         }
 
-        //const reverse = !!match[1];
-        return this.createGrouper();
+        const reverse = !!match[1];
+        return this.createGrouper(reverse);
     }
 
     /**
@@ -362,6 +362,6 @@ export abstract class Field {
             throw Error(`grouperRegExp() unimplemented for ${this.fieldNameSingular()}`);
         }
 
-        return new RegExp(`^group by ${this.fieldNameSingularEscaped()}$`);
+        return new RegExp(`^group by ${this.fieldNameSingularEscaped()}( reverse)?$`);
     }
 }

src/Query/Filter/MultiTextField.ts

@@ -63,15 +63,15 @@ export abstract class MultiTextField extends TextField {
     /**
      * This overloads {@link Field.createGrouper} to put a plural field name in the {@link Grouper.property}.
      */
-    public createGrouper(): Grouper {
-        return new Grouper(this.fieldNamePlural(), this.grouper());
+    public createGrouper(reverse: boolean = false): Grouper {
+        return new Grouper(this.fieldNamePlural(), this.grouper(), reverse);
     }
 
     protected grouperRegExp(): RegExp {
         if (!this.supportsGrouping()) {
             throw Error(`grouperRegExp() unimplemented for ${this.fieldNameSingular()}`);
         }
 
-        return new RegExp(`^group by ${this.fieldNamePlural()}$`);
+        return new RegExp(`^group by ${this.fieldNamePlural()}( reverse)?$`);
     }
 }

tests/Query.test.ts

@@ -201,25 +201,45 @@ describe('Query parsing', () => {
         // In alphabetical order, please
         const filters = [
             'group by created',
+            'group by created reverse',
             'group by backlink',
+            'group by backlink reverse',
             'group by done',
+            'group by done reverse',
             'group by due',
+            'group by due reverse',
             'group by filename',
+            'group by filename reverse',
             'group by folder',
+            'group by folder reverse',
             'group by happens',
+            'group by happens reverse',
             'group by heading',
+            'group by heading reverse',
             'group by path',
+            'group by path reverse',
             'group by priority',
+            'group by priority reverse',
             'group by recurrence',
+            'group by recurrence reverse',
             'group by recurring',
+            'group by recurring reverse',
             'group by root',
+            'group by root reverse',
             'group by scheduled',
+            'group by scheduled reverse',
             'group by start',
+            'group by start reverse',
             'group by status',
+            'group by status reverse',
             'group by status.name',
+            'group by status.name reverse',
             'group by status.type',
+            'group by status.type reverse',
             'group by tags',
+            'group by tags reverse',
             'group by urgency',
+            'group by urgency reverse',
         ];
         test.concurrent.each<string>(filters)('recognises %j', (filter) => {
             // Arrange

tests/Query/Filter/TagsField.test.ts

@@ -7,6 +7,8 @@ import { fromLine } from '../../TestHelpers';
 import { Sort } from '../../../src/Query/Sort';
 import { TaskBuilder } from '../../TestingTools/TaskBuilder';
 import { expectTaskComparesAfter, expectTaskComparesBefore } from '../../CustomMatchers/CustomMatchersForSorting';
+import type { Grouper } from '../../../src/Query/Grouper';
+import { TaskGroups } from '../../../src/Query/TaskGroups';
 
 describe('tag presence & absence', () => {
     it.each(['has tag', 'has tags'])('should have "%s" filtering', (filterLine: string) => {
@@ -644,4 +646,34 @@ describe('grouping by tag', () => {
         // Assert
         expect(grouper(fromLine({ line: taskLine }))).toEqual(groups);
     });
+
+    it('sorts headings in reverse', () => {
+        // Arrange
+        const a = fromLine({ line: '- [ ] a #tag1' });
+        const b = fromLine({ line: '- [ ] b #tag2' });
+        const inputs = [a, b];
+
+        // Act
+        const grouping: Grouper[] = [new TagsField().createGrouperFromLine('group by tags reverse')!];
+        const groups = new TaskGroups(grouping, inputs);
+
+        // Assert
+        expect(groups.toString()).toMatchInlineSnapshot(`
+            "
+            Group names: [#tag2]
+            #### #tag2
+            - [ ] b #tag2
+
+            ---
+
+            Group names: [#tag1]
+            #### #tag1
+            - [ ] a #tag1
+
+            ---
+
+            2 tasks
+            "
+        `);
+    });
 });

tests/TaskGroups.test.ts

@@ -171,7 +171,7 @@ describe('Grouping tasks', () => {
         const inputs = [a, b];
 
         // Act
-        const grouping: Grouper[] = [new DueDateField().createGrouper(true)];
+        const grouping: Grouper[] = [new DueDateField().createGrouperFromLine('group by due reverse')!];
         const groups = new TaskGroups(grouping, inputs);
 
         // Assert