[ospec] pinpoint the o.only() call site

ospec/change-log.md

@@ -3,6 +3,7 @@
 
 ## Upcoming...
 <!-- Add new lines here. Version number will be decided later -->
+- Pinpoint the `o.only()` call site
 - Improved wording, spacing and color-coding of report messages and errors ([#2147](https://github.com/MithrilJS/mithril.js/pull/2147), [@maranomynet](https://github.com/maranomynet))
 
 

ospec/ospec.js

@@ -34,7 +34,12 @@ else window.o = m()
 		ctx = parent
 	}
 	o.only = function(subject, predicate, silent) {
-		if (!silent) console.log(highlight("/!\\ WARNING /!\\ o.only() mode"))
+		if (!silent) {
+			console.log(highlight("/!\\ WARNING /!\\ o.only() mode"))
+			try {throw new Error} catch (e) {
+				console.log(this.cleanStackTrace(e) + "\n")
+			}
+		}
 		o(subject, only = predicate)
 	}
 	o.spy = function(fn) {