Boot as shell silently quits when the script is malformed

[alexander-yakushev]

Here's a valid test.clj:

(println "Loading")

(defn -main [& args]
  (println "Hello" args)))

When launched with boot -f test.clj it works correctly:

Loading
Hello (1 2 3)

But if I put an extra paren after the first form:

(println "Loading")) ;; <-- HERE

(defn -main [& args]
  (println "Hello" args)))

When running the same script I get:

Loading

And the exit code is zero. The expected behavior would be to signalize that the script is malformed.

[alandipert]

boot -b | cat -n yields the following:

     1	(ns boot.user (:use boot.core boot.util boot.task.built-in))
     2	
     3	(clojure.core/comment "start global profile")
     4	
     5	(require (quote boot.repl))
     6	
     7	(deftask cider "CIDER profile" [] (with-pass-thru [_] (swap! boot.repl/*default-dependencies* concat (quote [[org.clojure/tools.nrepl "0.2.12"] [cider/cider-nrepl "0.15.0-SNAPSHOT"] [refactor-nrepl "2.3.0-SNAPSHOT"]])) (swap! boot.repl/*default-middleware* concat (quote [cider.nrepl/cider-middleware refactor-nrepl.middleware/wrap-refactor]))))
     8	
     9	(clojure.core/comment "end global profile")
    10	
    11	(clojure.core/comment "start boot script")
    12	
    13	(println "Loading")
    14	
    15	(clojure.core/comment "end boot script")
    16	
    17	(clojure.core/let [boot?__1744__auto__ true] (clojure.core/if-not boot?__1744__auto__ (clojure.core/when-let [main__1745__auto__ (clojure.core/resolve (quote boot.user/-main))] (main__1745__auto__)) (boot.core/boot "boot.task.built-in/help")))

Notice that Line 13 is well-formed, but the build.boot content afterward is not spliced into the constructed boot script. The method we're using to read in the BOOT_FILE must be silently stopping when it encounters the unmatched paren.

[alexander-yakushev]

Thanks for looking into this!

[alandipert]

The problem starts at https://github.com/boot-clj/boot/blob/master/boot/core/src/boot/main.clj#L180 and lies with read-string via boot.util/read-string-all:

boot.user=> (require '[boot.util :as util])
nil
boot.user=> (util/read-string-all "(println :foo)) (println :bar)")
((println :foo))

read-string just reads the first object from the string and doesn't complain if there is an unexpected delimiter:

boot.user=> (read-string "foo)")
foo

My thinking is: what's the benefit of properly reading these files? We could just concatenate them string-wise and then the user will see syntax errors when the whole thing gets read and evaluated.

If there is a reason to read the forms before concatenating them, then we should probably switch to a read/stream based implementation of read-string-all that throws unmatched delimiter errors instead of truncating source files.

[bhagany]

I can file a separate bug for this if you'd like, but this is related to read-string-all - it doesn't handle aliased namespaced keywords, when the namespace was required within the string that's being read:

boot.user> (require '[boot.util :as util])
nil
boot.user> (util/read-string-all "::util/hi")
(:boot.util/hi)
boot.user> (util/read-string-all "::util/hi (require '[foo.core :as foo]) ::foo/hi")
java.lang.RuntimeException: Invalid token: ::foo/hi

I'm not sure if a read-based implementation would fix this, but hopefully the chances are good

[alandipert]

Discussed with @micha on Slack a bit, and I think we're in agreement - the way to go here is to move away from read entirely and just concatenate strings. That way any syntax or runtime errors pop up once, when the generated script is finally run.

@bhagany I think that would solve keywords thing too.

Micha also pointed out we can probably use load-string instead of writing the generated script to a temp file and calling load-file.

[alexander-yakushev]

Thanks for fixing this. I ❤️ Boot!