Dynamic commands in frontmatter YAML

Getting dynamic commands to work in the front matter YAML, it seems is either impossible or only inconsistently possible. For example, I have a frontmatter field mdate: that represents the last-modified date of the document. One might expect the following to work:

<%+ tp.file.last_modified_date() %>

but it doesn’t. I couldn’t seem to get Dataview inline queries to work in the frontmatter section either. A now-closed thread on this forum and others on r/ObsidianMD have been dead-ends if your goal is to dynamically update the frontmatter section of the document.

But, if you are comfortable working in the command-line shell, I wrote up a solution: Using fswatch to dynamically update Obsidian documents. I have the script that I posted in that article running against my vault and it works beautifully. You’re free to adapt and use it as you like.

I’ve tested it thoroughly on macOS; and I’ve tested bits and pieces of it on a Debian VM. As for Windows, I don’t know since I have no Windows machine to test it.

If someone has a solution that’s internal to Obsidian, I’m all ears, though!

let url;
let isGithub;
let isYoutube;

const kind = await tp.system.suggester(
	["Book", "Video", "Article"],
	["book", "video", "article"]

if (kind === "article" || kind === "video") {
	url = await tp.system.prompt("Url");

if (url) {
	isGithub = /.*github\.com.*/.test(url);
	isYoutube = /.*((youtu\.be)|(youtube\.com)).*/.test(url);

tR += `kind: ${kind}`;

if (isGithub) {
	tR += `\ngithub: true`;
	tR += `\nAlias: {{VALUE:TITLE}} (repo)`;
if (isYoutube) {
	tR += `\nyoutube: true`;
	tR += `\nAlias: {{VALUE:TITLE}} (youtube)`;
if (kind === "book") {
	const year = await tp.system.prompt("Year");
	const publisher = await tp.system.prompt("Publisher");
	tR += `\nyear: ${year}`;
	tR += `\npublisher: ${publisher}`;
	tR += `\nAlias: {{VALUE:TITLE}} (book)`;

tR += `\nconsumed: false`

Here is a frontmatter piece of a template of my using dynamic templater values in frontmatter.

Another little trick I just discovered is using DataViewJS queried data in templater, is letting dataview append its data to the window object and consuming this inside templater.