Relay compiler panics if the schema file path starts with ./ and watchman is being used

[captbaritone]

It seems Watchman does not interpret paths with ./ in the same what that our checks for the existence of the file does. The result is that our initial validation ensuring we have a schema file passes, but when we initialize the project, no schema file is discovered by Watchman and thus when the compiler goes to look up the schema it panics.

I haven't been able to locate exactly the specification for what type of path Watchman expects, but I think we need to either find a way to correctly transform arbitrary paths into that format, or add validation which rejects configs which are not already in that format.

This is potentially a pretty big footgun for adopters of Relay. I myself hit it trying to setup a small project to repro an unrelated issue.

The invalid watchman file paths get constructed here:

relay/compiler/crates/relay-compiler/src/file_source/watchman_query_builder.rs

Line 56 in 9b90142

paths: config.get_schema_file_paths(),

Validating that the schema file exists is done here:

relay/compiler/crates/relay-compiler/src/config.rs

Lines 588 to 599 in 9b90142

	let abs_schema_file = self.root_dir.join(schema_file);
	if !abs_schema_file.exists() {
	errors.push(ConfigValidationError::SchemaFileNotExistent {
	project_name,
	schema_file: abs_schema_file.clone(),
	});
	} else if !abs_schema_file.is_file() {
	errors.push(ConfigValidationError::SchemaFileNotFile {
	project_name,
	schema_file: abs_schema_file.clone(),
	});
	}