The Clojure compiler is not very helpful when it comes to debugging
exceptions that occur while macros are being expanded. As an example,
consider this code:
;; macro-fail.clj
(defmacro broken [] (/ 0 0))
(broken)
Here's the stack trace I get when I compile this file:
Exception in thread "main" java.lang.ArithmeticException: Divide by
zero (macro-fail.clj:0)
at clojure.lang.Compiler.eval(Compiler.java:5365)
at clojure.lang.Compiler.load(Compiler.java:5759)
at clojure.lang.Compiler.loadFile(Compiler.java:5722)
at clojure.main$load_script__5893.invoke(main.clj:213)
at clojure.main$script_opt__5922.invoke(main.clj:265)
at clojure.main$main__5940.doInvoke(main.clj:346)
at clojure.lang.RestFn.invoke(RestFn.java:409)
at clojure.lang.Var.invoke(Var.java:365)
at clojure.lang.AFn.applyToHelper(AFn.java:165)
at clojure.lang.Var.applyTo(Var.java:482)
at clojure.main.main(main.java:37)
Caused by: java.lang.ArithmeticException: Divide by zero
at clojure.lang.Numbers.divide(Numbers.java:138)
at user$broken__1.invoke(macro-fail.clj:2)
at clojure.lang.Var.invoke(Var.java:369)
at clojure.lang.AFn.applyToHelper(AFn.java:167)
at clojure.lang.Var.applyTo(Var.java:482)
at clojure.lang.Compiler.macroexpand1(Compiler.java:5212)
at clojure.lang.Compiler.macroexpand(Compiler.java:5267)
at clojure.lang.Compiler.eval(Compiler.java:5335)
... 10 more
As you can see, line 3, where the macro is used, appears nowhere in
the stack trace. I've made some progress addressing this issue by
adding an exception handler in Compiler.macroexpand1. I also
discovered that, although the reader attaches line numbers to the
forms it reads, it does not attach file names. I've added some code in
LispReader.java that attaches the file name, but it does so by getting
the value of Compiler.SOURCE_PATH. I suspect a less hackish fix would
involve passing a filename to the reader some other way.
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