[#112] Add binding, with-out-str and with-in-str

reflection.json

@@ -64,6 +64,12 @@
     "allPublicFields": true,
     "allPublicConstructors": true
   },
+  {
+    "name":"clojure.lang.LineNumberingPushbackReader",
+    "allPublicMethods":true,
+    "allPublicFields": true,
+    "allPublicConstructors": true
+  },
   {
     "name":"java.util.concurrent.LinkedBlockingQueue",
     "allPublicMethods":true
@@ -87,8 +93,19 @@
     "allPublicMethods":true,
     "allPublicFields": true,
     "allPublicConstructors": true
-  }
+  },
-  ,
+  {
+    "name":"java.io.StringReader",
+    "allPublicMethods":true,
+    "allPublicFields": true,
+    "allPublicConstructors": true
+  },
+  {
+    "name":"java.io.StringWriter",
+    "allPublicMethods":true,
+    "allPublicFields": true,
+    "allPublicConstructors": true
+  },
   {
     "name":"java.lang.System",
     "allPublicMethods":true,

sci

@@ -1 +1 @@
-Subproject commit ad83ca84f8a9e6baf220b4757cde0f17b1558d6b
+Subproject commit 8e4b8ff55b5afbd330a278d835fbb6fe0858df99

src/babashka/impl/clojure/core.clj

@@ -32,9 +32,39 @@
    `(when-not ~x
       (throw (~'__assertion-error__ (str "Assert failed: " ~message "\n" (pr-str '~x)))))))
 
+(defn binding*
+  "This macro only works with symbols that evaluate to vars themselves. See `*in*` and `*out*` below."
+  [_ _ bindings & body]
+  `(do
+     (let []
+       (push-thread-bindings (hash-map ~@bindings))
+       (try
+         ~@body
+         (finally
+           (pop-thread-bindings))))))
+
+;; this works now!
+"(def w (java.io.StringWriter.)) (push-thread-bindings {clojure.core/*out* w}) (try (println \"hello\") (finally (pop-thread-bindings))) (prn \">\" (str w))"
+
+;; this also works now! "(def w (java.io.StringWriter.)) (binding [clojure.core/*out* w] (println \"hello\")) (str w)"
+
+(defn with-out-str*
+  [_ _ & body]
+  `(let [s# (java.io.StringWriter.)]
+     (binding [*out* s#]
+       ~@body
+       (str s#))))
+
+(defn with-in-str*
+  [_ _ s & body]
+  `(with-open [s# (-> (java.io.StringReader. ~s) clojure.lang.LineNumberingPushbackReader.)]
+     (binding [*in* s#]
+       ~@body)))
+
 (def core-extras
-  {'*in* *in*
+  {'*in* #'*in*
-   '*out* *out*
+   '*out* #'*out*
+   'binding (with-meta binding* {:sci/macro true})
    'file-seq file-seq
    'future-call future-call
    'future (with-meta future {:sci/macro true})
@@ -56,9 +86,13 @@
    'print print
    'println println
    'println-str println-str
+   'pop-thread-bindings pop-thread-bindings
+   'push-thread-bindings push-thread-bindings
    'flush flush
    'read-line read-line
    '__close!__ __close!__
    'with-open (with-meta with-open* {:sci/macro true})
+   'with-out-str (with-meta with-out-str* {:sci/macro true})
+   'with-in-str (with-meta with-in-str* {:sci/macro true})
    '__assertion-error__ __assertion-error__
    'assert (with-meta assert* {:sci/macro true})})

src/babashka/main.clj

@@ -223,8 +223,11 @@ Everything after that is bound to *command-line-args*."))
                        'clojure.lang.ExceptionInfo clojure.lang.ExceptionInfo
                        'java.lang.Integer Integer
                        'java.io.File java.io.File
+                       'clojure.lang.LineNumberingPushbackReader clojure.lang.LineNumberingPushbackReader
                        'java.util.regex.Pattern java.util.regex.Pattern
                        'java.lang.String String
+                       'java.io.StringReader java.io.StringReader
+                       'java.io.StringWriter java.io.StringWriter
                        'java.lang.System System
                        'java.lang.Thread Thread}
              :imports '{ArithmeticException java.lang.ArithmeticException

test/babashka/main_test.clj

@@ -257,3 +257,15 @@
                        nil)"
                     path))
     (is (= "foobar\nbarfoo\n" (slurp path)))))
+
+(deftest binding-test
+  (is (=  6 (bb nil "(def w (java.io.StringWriter.))
+                 (binding [clojure.core/*out* w]
+                   (println \"hello\"))
+                 (count (str w))"))))
+
+(deftest with-out-str-test
+  (is (= 6 (bb nil "(count (with-out-str (println \"hello\")))"))))
+
+(deftest with-in-str-test
+  (is (= 5 (bb nil "(count (with-in-str \"hello\" (read-line)))"))))