Question: how does Obsidian know the file path of a wikilink?

[zeromh]

This isn't an Issue, but I'd like to understand how Obsidian.md keeps track of wikilink file paths, and how obsidian-export deals with that.

1. Wikilink file paths aren't included in the MD files themselves. So does Obsidian store wikilink file paths in its system files?
2. Does obsidian-export make use of this system information? Or does it traverse all the files in the vault and make a map of the file paths?

[zoni]

Obsidian stores all this data in the Markdown notes themselves. It may keep metadata around that as a cache for performance reasons, but all of those relations can be rebuilt from notes if the cache is deleted.

Given that Obsidian is closed-source we can't really look at how it does this without reverse-engineering, but the lookup algorithm is pretty straightforward. Here's what obsidian-export does:

obsidian-export/src/lib.rs

Lines 722 to 739 in 86af6bb

	fn lookup_filename_in_vault<'a>(
	filename: &str,
	vault_contents: &'a [PathBuf],
	) -> Option<&'a PathBuf> {
	// Markdown files don't have their .md extension added by Obsidian, but other files (images,
	// PDFs, etc) do so we match on both possibilities.
	//
	// References can also refer to notes in a different case (to lowercase text in a
	// sentence even if the note is capitalized for example) so we also try a case-insensitive
	// lookup.
	vault_contents.iter().find(|path| {
	let path_lowered = PathBuf::from(path.to_string_lossy().to_lowercase());
	path.ends_with(&filename)
	|| path_lowered.ends_with(&filename.to_lowercase())
	|| path.ends_with(format!("{}.md", &filename))
	|| path_lowered.ends_with(format!("{}.md", &filename.to_lowercase()))
	})
	}

Basically, it indexes all the filenames in your vault, then finds the longest-matching [[WikiLink]] match, taking into account a few special rules like being case-insensitive and only have a file extension when a note isn't a Markdown file.

Obsidian itself ensures WikiLinks are unique and will prefix the directory a note is in when you have two similarly-named notes in different folders.

[zeromh]

Obsidian stores all this data in the Markdown notes themselves.

I don't think that's true? If your link settings are set to "Shortest path when possible" (which I believe is the default), the link information in the Markdown notes doesn't contain the file location. For example, say that in the current note I make a link to a note located at ../Chemistry/crystal_structure.md. In the current markdown file, this link looks like [[crystal_structure]]. No information on the location of the file. So I think Obsidian must be storing this in its system files. Am I misunderstanding something here?

Basically, it indexes all the filenames in your vault, then finds the longest-matching [[WikiLink]] match

Just checking if I understand you... So if a file links to [[crystal_structure]], obsidian-export will determine the location of crystal_structure.md because it indexes all the files in the vault. Right?