Add disassemble function to hy.core.language

This function dumps the AST or the python code generated by evaluating a quoted expression to stdout.

Fixes #58

hy/core/language.hy

@@ -45,6 +45,19 @@
   (_numeric-check n)
   (- n 1))
 
+(defn disassemble [tree &optional [codegen false]]
+  "Dump the python AST for a given Hy tree to standard output
+   If the second argument is true, generate python code instead."
+  (import astor)
+  (import hy.compiler)
+
+  (fake-source-positions tree)
+  (setv compiled (hy.compiler.hy_compile tree (calling-module-name)))
+  (print ((if codegen
+            astor.codegen.to_source
+            astor.dump)
+          compiled)))
+
 (defn distinct [coll]
   "Return a generator from the original collection with duplicates
    removed"
@@ -81,6 +94,15 @@
   (_numeric-check n)
   (= (% n 2) 0))
 
+(defn fake-source-positions [tree]
+  "Fake the source positions for a given tree"
+  (if (and (iterable? tree) (not (string? tree)))
+    (for* [subtree tree]
+          (fake-source-positions subtree)))
+  (for* [attr '[start-line end-line start-column end-column]]
+        (if (not (hasattr tree attr))
+          (setattr tree attr 1))))
+
 (defn filter [pred coll]
   "Return all elements from `coll` that pass `pred`"
   (let [[citer (iter coll)]]
@@ -276,7 +298,7 @@
   (_numeric_check n)
   (= n 0))
 
-(def *exports* '[calling-module-name cycle dec distinct drop
+(def *exports* '[calling-module-name cycle dec distinct disassemble drop
                  drop-while empty? even? filter flatten float? gensym
                  inc instance? integer integer? iterable? iterate
                  iterator? macroexpand macroexpand-1 neg? nil? none?

tests/native_tests/language.hy

@@ -868,3 +868,23 @@
   "NATIVE: Test the calling-module-name function"
   (assert (= (calling-module-name -1) "hy.core.language"))
   (assert (= (calling-module-name 0) "tests.native_tests.language")))
+
+
+(defn test-disassemble []
+  "NATIVE: Test the disassemble function"
+  (import sys)
+  (if-python2
+   (import [io [BytesIO :as StringIO]])
+   (import [io [StringIO]]))
+  (setv prev-stdout sys.stdout)
+  (setv sys.stdout (StringIO))
+  (disassemble '(do (leaky) (leaky) (macros)))
+  (setv stdout (.getvalue sys.stdout))
+  (setv sys.stdout prev-stdout)
+  (assert (in "leaky" stdout))
+  (assert (in "macros" stdout))
+  (setv sys.stdout (StringIO))
+  (disassemble '(do (leaky) (leaky) (macros)) true)
+  (setv stdout (.getvalue sys.stdout))
+  (setv sys.stdout prev-stdout)
+  (assert (= stdout "leaky()\nleaky()\nmacros()\n")))