feat(#1437): Unify template syntax to use {{variable}} everywhere

Filename templates now support both {{variable}} (preferred) and
{variable} (legacy) syntax for backwards compatibility. This makes
the syntax consistent with body/frontmatter templates.

Changes:
- filenameGenerator.ts: Process {{var}} first, then {var} as fallback
- titlePropertyCard.ts: Add deprecation warning for single-brace syntax
- en.ts: Add translation for legacy syntax warning
- docs/task-defaults.md: Update examples to use {{variable}} syntax

The single-brace syntax remains functional but users will see a warning
in settings encouraging migration to double-brace syntax.

docs/settings/task-defaults.md

@@ -123,87 +123,89 @@ The system prevents file overwrites by checking for existing files and showing e
 
 When using the **custom** filename format, you can create templates using variables that are replaced with actual values when tasks are created.
 
+> **Recommended syntax:** Use double braces `{{variable}}` for consistency with body templates. Single braces `{variable}` are supported for backwards compatibility but are deprecated.
+
 ### Available Filename Variables
 
 **Task Properties:**
 
-- `{title}` - Task title (sanitized for filenames)
-- `{priority}` - Task priority (e.g., "high", "medium", "low")
-- `{status}` - Task status (e.g., "todo", "in-progress", "done")
-- `{dueDate}` - Task due date (YYYY-MM-DD format)
-- `{scheduledDate}` - Task scheduled date (YYYY-MM-DD format)
-- `{priorityShort}` - First letter of priority in uppercase (e.g., "H")
-- `{statusShort}` - First letter of status in uppercase (e.g., "T")
-- `{titleLower}` - Task title in lowercase
-- `{titleUpper}` - Task title in uppercase
-- `{titleSnake}` - Task title in snake_case
-- `{titleKebab}` - Task title in kebab-case
-- `{titleCamel}` - Task title in camelCase
-- `{titlePascal}` - Task title in PascalCase
+- `{{title}}` - Task title (sanitized for filenames)
+- `{{priority}}` - Task priority (e.g., "high", "medium", "low")
+- `{{status}}` - Task status (e.g., "todo", "in-progress", "done")
+- `{{dueDate}}` - Task due date (YYYY-MM-DD format)
+- `{{scheduledDate}}` - Task scheduled date (YYYY-MM-DD format)
+- `{{priorityShort}}` - First letter of priority in uppercase (e.g., "H")
+- `{{statusShort}}` - First letter of status in uppercase (e.g., "T")
+- `{{titleLower}}` - Task title in lowercase
+- `{{titleUpper}}` - Task title in uppercase
+- `{{titleSnake}}` - Task title in snake_case
+- `{{titleKebab}}` - Task title in kebab-case
+- `{{titleCamel}}` - Task title in camelCase
+- `{{titlePascal}}` - Task title in PascalCase
 
 **Date and Time:**
 
-- `{date}` - Full date (YYYY-MM-DD format, e.g., "2025-08-15")
-- `{time}` - Time as HHMMSS (e.g., "143502")
-- `{timestamp}` - Date and time as YYYY-MM-DD-HHMMSS (e.g., "2025-08-15-143502")
-- `{dateTime}` - Date and time as YYYY-MM-DD-HHMM (e.g., "2025-08-15-1435")
-- `{year}` - Year (e.g., "2025")
-- `{month}` - Month with leading zero (e.g., "08")
-- `{day}` - Day with leading zero (e.g., "15")
-- `{hour}` - Hour with leading zero (e.g., "14")
-- `{minute}` - Minute with leading zero (e.g., "35")
-- `{second}` - Second with leading zero (e.g., "02")
-- `{shortDate}` - Short date as YYMMDD (e.g., "250815")
-- `{shortYear}` - Short year as YY (e.g., "25")
-- `{monthName}` - Full month name (e.g., "August")
-- `{monthNameShort}` - Short month name (e.g., "Aug")
-- `{dayName}` - Full day name (e.g., "Thursday")
-- `{dayNameShort}` - Short day name (e.g., "Thu")
-- `{week}` - Week number (e.g., "33")
-- `{quarter}` - Quarter number (e.g., "3")
-- `{time12}` - 12-hour time with AM/PM (e.g., "02:35 PM")
-- `{time24}` - 24-hour time (e.g., "14:35")
-- `{hourPadded}` - Hour with leading zero (e.g., "14")
-- `{hour12}` - 12-hour format hour with leading zero (e.g., "02")
-- `{ampm}` - AM/PM indicator (e.g., "PM")
+- `{{date}}` - Full date (YYYY-MM-DD format, e.g., "2025-08-15")
+- `{{time}}` - Time as HHMMSS (e.g., "143502")
+- `{{timestamp}}` - Date and time as YYYY-MM-DD-HHMMSS (e.g., "2025-08-15-143502")
+- `{{dateTime}}` - Date and time as YYYY-MM-DD-HHMM (e.g., "2025-08-15-1435")
+- `{{year}}` - Year (e.g., "2025")
+- `{{month}}` - Month with leading zero (e.g., "08")
+- `{{day}}` - Day with leading zero (e.g., "15")
+- `{{hour}}` - Hour with leading zero (e.g., "14")
+- `{{minute}}` - Minute with leading zero (e.g., "35")
+- `{{second}}` - Second with leading zero (e.g., "02")
+- `{{shortDate}}` - Short date as YYMMDD (e.g., "250815")
+- `{{shortYear}}` - Short year as YY (e.g., "25")
+- `{{monthName}}` - Full month name (e.g., "August")
+- `{{monthNameShort}}` - Short month name (e.g., "Aug")
+- `{{dayName}}` - Full day name (e.g., "Thursday")
+- `{{dayNameShort}}` - Short day name (e.g., "Thu")
+- `{{week}}` - Week number (e.g., "33")
+- `{{quarter}}` - Quarter number (e.g., "3")
+- `{{time12}}` - 12-hour time with AM/PM (e.g., "02:35 PM")
+- `{{time24}}` - 24-hour time (e.g., "14:35")
+- `{{hourPadded}}` - Hour with leading zero (e.g., "14")
+- `{{hour12}}` - 12-hour format hour with leading zero (e.g., "02")
+- `{{ampm}}` - AM/PM indicator (e.g., "PM")
 
 **Advanced:**
 
-- `{unix}` - Unix timestamp in seconds (e.g., "1692106502")
-- `{unixMs}` - Unix timestamp in milliseconds (e.g., "1692106502123")
-- `{milliseconds}` - Milliseconds (e.g., "123")
-- `{ms}` - Milliseconds (e.g., "123")
-- `{timezone}` - Timezone offset (e.g., "+10:00")
-- `{timezoneShort}` - Short timezone offset (e.g., "+1000")
-- `{utcOffset}` - UTC offset (e.g., "+10:00")
-- `{utcOffsetShort}` - Short UTC offset (e.g., "+1000")
-- `{utcZ}` - UTC Z indicator (always "Z")
-- `{zettel}` - Zettelkasten ID (e.g., "250815abc")
-- `{nano}` - Nano ID with timestamp and random string
+- `{{unix}}` - Unix timestamp in seconds (e.g., "1692106502")
+- `{{unixMs}}` - Unix timestamp in milliseconds (e.g., "1692106502123")
+- `{{milliseconds}}` - Milliseconds (e.g., "123")
+- `{{ms}}` - Milliseconds (e.g., "123")
+- `{{timezone}}` - Timezone offset (e.g., "+10:00")
+- `{{timezoneShort}}` - Short timezone offset (e.g., "+1000")
+- `{{utcOffset}}` - UTC offset (e.g., "+10:00")
+- `{{utcOffsetShort}}` - Short UTC offset (e.g., "+1000")
+- `{{utcZ}}` - UTC Z indicator (always "Z")
+- `{{zettel}}` - Zettelkasten ID (e.g., "250815abc")
+- `{{nano}}` - Nano ID with timestamp and random string
 
 ### Filename Template Examples
 
 **Date-based with title:**
 ```
-{year}-{month}-{day} {title}
+{{year}}-{{month}}-{{day}} {{title}}
 ```
 Result: `2025-08-15 Complete documentation.md`
 
 **Zettelkasten with title:**
 ```
-{zettel} {title}
+{{zettel}} {{title}}
 ```
 Result: `250815abc Complete documentation.md`
 
 **Priority and status prefix:**
 ```
-[{priorityShort}] {title}
+[{{priorityShort}}] {{title}}
 ```
 Result: `[H] Complete documentation.md`
 
 **Custom timestamp:**
 ```
-{timestamp}-{titleKebab}
+{{timestamp}}-{{titleKebab}}
 ```
 Result: `2025-08-15-143502-complete-documentation.md`
 
@@ -211,14 +213,14 @@ Result: `2025-08-15-143502-complete-documentation.md`
 
 For ICS event notes, additional variables are available:
 
-- `{icsEventTitle}` - Event title from ICS calendar
-- `{icsEventLocation}` - Event location
-- `{icsEventDescription}` - Event description (truncated to 50 characters)
-- `{icsEventTitleWithDate}` - Event title with formatted date
+- `{{icsEventTitle}}` - Event title from ICS calendar
+- `{{icsEventLocation}}` - Event location
+- `{{icsEventDescription}}` - Event description (truncated to 50 characters)
+- `{{icsEventTitleWithDate}}` - Event title with formatted date
 
 ### Important Notes
 
-- **Single Braces**: Filename variables use single braces `{variable}` while folder variables use double braces `{{variable}}`
+- **Unified Syntax**: Both filename and body templates now use double braces `{{variable}}`. Single braces `{variable}` are supported for backwards compatibility but deprecated.
 - **Sanitization**: All variables are automatically sanitized to be safe for filenames (invalid characters removed)
 - **Empty Values**: If a property doesn't have a value, the variable is replaced with an empty string
 - **Character Limits**: Filenames are limited to 255 characters on most systems

src/i18n/resources/en.ts

@@ -1011,6 +1011,7 @@ export const en: TranslationTree = {
 				filenameUpdatesWithTitle: "Filename will automatically update when the task title changes.",
 				filenameFormat: "Filename format:",
 				customTemplate: "Custom template:",
+				legacySyntaxWarning: "Single-brace syntax like {title} is deprecated. Please use double-brace syntax {{title}} instead for consistency with body templates.",
 			},
 			tagsCard: {
 				nativeObsidianTags: "Uses native Obsidian tags",

src/settings/tabs/taskProperties/titlePropertyCard.ts

@@ -1,3 +1,4 @@
+import { setIcon } from "obsidian";
 import TaskNotesPlugin from "../../../main";
 import {
 	createCard,
@@ -153,10 +154,42 @@ function renderFilenameSettingsContent(
 			plugin.settings.customFilenameTemplate
 		);
 		templateInput.style.width = "100%";
+
+		// Warning container for legacy syntax
+		const warningContainer = container.createDiv();
+
+		const updateWarning = () => {
+			warningContainer.empty();
+			// Check for single-brace syntax that isn't part of double-brace
+			// Match {word} but not {{word}}
+			const template = templateInput.value;
+			const hasLegacySyntax = /(?<!\{)\{([a-zA-Z]+)\}(?!\})/.test(template);
+
+			if (hasLegacySyntax) {
+				const warningEl = warningContainer.createDiv({
+					cls: "setting-item-description mod-warning",
+				});
+				warningEl.style.color = "var(--text-warning)";
+				warningEl.style.marginTop = "8px";
+				warningEl.style.display = "flex";
+				warningEl.style.alignItems = "flex-start";
+				warningEl.style.gap = "6px";
+
+				const iconEl = warningEl.createSpan();
+				setIcon(iconEl, "alert-triangle");
+				iconEl.style.flexShrink = "0";
+
+				const textEl = warningEl.createSpan();
+				textEl.textContent = translate("settings.taskProperties.titleCard.legacySyntaxWarning");
+			}
+		};
+
 		templateInput.addEventListener("change", () => {
 			plugin.settings.customFilenameTemplate = templateInput.value;
 			save();
+			updateWarning();
 		});
+		templateInput.addEventListener("input", updateWarning);
 		templateContainer.appendChild(templateInput);
 
 		// Help text for template variables
@@ -164,5 +197,8 @@ function renderFilenameSettingsContent(
 			text: translate("settings.appearance.taskFilenames.customTemplate.helpText"),
 			cls: "setting-item-description",
 		});
+
+		// Initial warning check
+		updateWarning();
 	}
 }

src/utils/filenameGenerator.ts

@@ -288,17 +288,24 @@ function generateCustomFilename(
 		}
 
 		// Replace all variables in the template
+		// Support both {{variable}} (preferred) and {variable} (legacy) syntax
 		Object.entries(variables).forEach(([key, value]) => {
 			try {
-				const regex = new RegExp(`\\{${key}\\}`, "g");
-				result = result.replace(regex, value);
+				// First: Replace double-brace syntax {{variable}} (preferred, consistent with body templates)
+				const doubleRegex = new RegExp(`\\{\\{${key}\\}\\}`, "g");
+				result = result.replace(doubleRegex, value);
+
+				// Second: Replace single-brace syntax {variable} (legacy, backwards compatibility)
+				const singleRegex = new RegExp(`\\{${key}\\}`, "g");
+				result = result.replace(singleRegex, value);
 			} catch (regexError) {
 				console.warn(`Error replacing template variable ${key}:`, regexError);
 			}
 		});
 
-		// Clean up any remaining unreplaced variables
-		result = result.replace(/\{[^}]+\}/g, "");
+		// Clean up any remaining unreplaced variables (both syntaxes)
+		result = result.replace(/\{\{[^}]+\}\}/g, ""); // {{variable}}
+		result = result.replace(/\{[^}]+\}/g, ""); // {variable}
 
 		// Ensure we have a valid filename
 		if (!result.trim()) {