Improve help text + print help when no args (#61)

README.md

@@ -96,7 +96,7 @@ You may also download a binary from [Github](https://github.com/borkdude/babashk
 ## Usage
 
 ``` shellsession
-Usage: bb [ -i | -I ] [ -o | -O ] [ --stream ] ( expression | -f <file> | --socket-repl [host:]port )
+Usage: bb [ -i | -I ] [ -o | -O ] [ --stream ] ( -e <expression> | -f <file> | --socket-repl [<host>:]<port> )
 
 Options:
 
@@ -108,9 +108,13 @@ Options:
   -o: write lines to stdout.
   -O: write EDN values to stdout.
   --stream: stream over lines or EDN values from stdin. Combined with -i or -I *in* becomes a single value per iteration.
-  --file or -f: read expressions from file instead of argument wrapped in an implicit do.
+  -e, --eval <expression>: evaluate an expression
+  -f, --file <path>: evaluate a file
   --socket-repl: start socket REPL. Specify port (e.g. 1666) or host and port separated by colon (e.g. 127.0.0.1:1666).
   --time: print execution time before exiting.
+
+If neither -e, -f, or --socket-repl are specified, then the first argument that is not parsed as a option is treated as a file if it exists, or as an expression otherwise.
+Everything after that is bound to *command-line-args*.
 ```
 
 The `clojure.core` functions are accessible without a namespace alias.

src/babashka/main.clj

@@ -101,7 +101,7 @@
 (defn print-version []
   (println (str "babashka v"(str/trim (slurp (io/resource "BABASHKA_VERSION"))))))
 
-(def usage-string "Usage: bb [ -i | -I ] [ -o | -O ] [ --stream ] ( -e <expression> | -f <file> | --socket-repl [host:]port )")
+(def usage-string "Usage: bb [ -i | -I ] [ -o | -O ] [ --stream ] ( -e <expression> | -f <file> | --socket-repl [<host>:]<port> )")
 (defn print-usage []
   (println usage-string))
 
@@ -121,13 +121,13 @@
   -o: write lines to stdout.
   -O: write EDN values to stdout.
   --stream: stream over lines or EDN values from stdin. Combined with -i or -I *in* becomes a single value per iteration.
-  -e, --eval expression: evaluate an expression
+  -e, --eval <expression>: evaluate an expression
-  -f, --file path: evaluate a file
+  -f, --file <path>: evaluate a file
   --socket-repl: start socket REPL. Specify port (e.g. 1666) or host and port separated by colon (e.g. 127.0.0.1:1666).
   --time: print execution time before exiting.
 
-  If neither -e, -f, or --socket-repl are specified, then the first argument is treated as a file if it exists, or as an expression otherwise.
+If neither -e, -f, or --socket-repl are specified, then the first argument that is not parsed as a option is treated as a file if it exists, or as an expression otherwise.
-"))
+Everything after that is bound to *command-line-args*."))
 
 (defn read-file [file]
   (let [f (io/file file)]
@@ -211,16 +211,15 @@
                 :else
                 (try
                   (let [expr (if file (read-file file) expression)]
+                    (if expr
                       (loop [in (read-next *in*)]
                         (let [ctx (update ctx :bindings assoc (with-meta '*in*
                                                                 (when-not stream?
                                                                   {:sci/deref! true})) in)]
                           (if (identical? ::EOF in)
                             [nil 0] ;; done streaming
-                          (let [res [(do (when-not (or expression file)
+                            (let [res [(let [res (sci/eval-string expr ctx)]
-                                           (throw (Exception. (str args  "Babashka expected an expression. Type --help to print help."))))
+                                         (when (some? res)
-                                         (let [res (sci/eval-string expr ctx)]
-                                           (if (some? res)
                                            (if-let [pr-f (cond shell-out println
                                                                edn-out prn)]
                                              (if (coll? res)
@@ -228,10 +227,11 @@
                                                        :while (not (pipe-signal-received?))]
                                                  (pr-f l))
                                                (pr-f res))
-                                               (prn res))))) 0]]
+                                             (prn res)))) 0]]
                               (if stream?
                                 (recur (read-next *in*))
-                              res))))))
+                                res)))))
+                      [(print-help) 1]))
                   (catch Throwable e
                     (binding [*out* *err*]
                       (let [d (ex-data e)

test/babashka/main_test.clj

@@ -101,8 +101,12 @@
 (deftest malformed-command-line-args-test
   (is (thrown-with-msg? Exception #"File does not exist: non-existing\n"
                         (bb nil "-f" "non-existing")))
-  (is (thrown-with-msg? Exception #"expression"
+  (testing "no arguments prints help"
-                        (bb nil))))
+    (is (str/includes?
+         (try (test-utils/bb nil)
+              (catch clojure.lang.ExceptionInfo e
+                (:stdout (ex-data e))))
+         "Usage:"))))
 
 (deftest ssl-test
   (let [graalvm-home (System/getenv "GRAALVM_HOME")

test/babashka/test_utils.clj

@@ -6,15 +6,19 @@
 (set! *warn-on-reflection* true)
 
 (defn bb-jvm [input & args]
-  (let [sw (java.io.StringWriter.)
+  (let [es (java.io.StringWriter.)
-        res (binding [*err* sw]
+        os (java.io.StringWriter.)]
-              (with-out-str
+    (binding [*err* es
-                (if input
+              *out* os]
+      (let [res (if input
                   (with-in-str input
                     (apply main/main args))
-                  (apply main/main args))))]
+                  (apply main/main args))]
-    (if-let [err ^String (not-empty (str sw))]
+        (if (zero? res)
-      (throw (Exception. err)) res)))
+          (str os)
+          (throw (ex-info (str es)
+                          {:stdout (str os)
+                           :stderr (str es)})))))))
 
 (defn bb-native [input & args]
   (let-programs [bb "./bb"]