Fix #1243: read raises EOFError on false inputs (#1244)

* Fix #1243: `read` raises EOFError on false inputs

* Fix crash when trying to `eval` false values

NEWS

@@ -15,6 +15,8 @@ Changes from 0.12.1
    * Shadowed comparison operators now use `and` instead of `&`
      for chained comparisons
    * partition no longer prematurely exhausts input iterators
+   * read and read-str no longer raise an error when the input
+     parses to a false value (e.g., the empty string)
 
 Changes from 0.12.0
 

hy/compiler.py

@@ -24,9 +24,9 @@
 # FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 # DEALINGS IN THE SOFTWARE.
 
-from hy.models import (HyExpression, HyKeyword, HyInteger, HyComplex, HyString,
-                       HyBytes, HySymbol, HyFloat, HyList, HySet, HyDict,
-                       HyCons)
+from hy.models import (HyObject, HyExpression, HyKeyword, HyInteger, HyComplex,
+                       HyString, HyBytes, HySymbol, HyFloat, HyList, HySet,
+                       HyDict, HyCons)
 from hy.errors import HyCompileError, HyTypeError
 
 from hy.lex.parser import hy_symbol_mangle
@@ -2689,7 +2689,10 @@ def hy_compile(tree, module_name, root=ast.Module, get_expr=False):
     body = []
     expr = None
 
-    if tree:
+    if not (isinstance(tree, HyObject) or type(tree) is list):
+        raise HyCompileError("tree must be a HyObject or a list")
+
+    if isinstance(tree, HyObject) or tree:
         compiler = HyASTCompiler(module_name)
         result = compiler.compile(tree)
         expr = result.force_expr
@@ -2697,10 +2700,9 @@ def hy_compile(tree, module_name, root=ast.Module, get_expr=False):
         if not get_expr:
             result += result.expr_as_stmt()
 
-        if isinstance(tree, list):
-            spoof_tree = tree[0]
-        else:
-            spoof_tree = tree
+        # We need to test that the type is *exactly* `list` because we don't
+        # want to do `tree[0]` on HyList or such.
+        spoof_tree = tree[0] if type(tree) is list else tree
         body = compiler.imports_as_stmts(spoof_tree) + result.stmts
 
     ret = root(body=body)

hy/core/language.hy

@@ -435,17 +435,17 @@
                       [eof ""]]
   "Read from input and returns a tokenized string.
    Can take a given input buffer to read from"
-  (def buff "")
+  (setv buff "")
   (while True
-    (def inn (str (.readline from-file)))
+    (setv inn (string (.readline from-file)))
     (if (= inn eof)
-      (raise (EOFError "Reached end of file" )))
-    (setv buff (+ buff inn))
+      (raise (EOFError "Reached end of file")))
+    (+= buff inn)
     (try
-      (def parsed (first (tokenize buff)))
+      (setv parsed (first (tokenize buff)))
       (except [e [PrematureEndOfInput IndexError]])
-      (else (if parsed (break)))))
-    parsed)
+      (else (break))))
+  parsed)
 
 (defn read-str [input]
   "Reads and tokenizes first line of input"

tests/native_tests/language.hy

@@ -1055,6 +1055,19 @@
   (assert (= None (eval (quote (print ""))))))
 
 
+(defn test-eval-false []
+  (assert (is (eval 'False) False))
+  (assert (is (eval 'None) None))
+  (assert (= (eval '0) 0))
+  (assert (= (eval '"") ""))
+  (assert (= (eval 'b"") b""))
+  (assert (= (eval ':) :))
+  (assert (= (eval '[]) []))
+  (assert (= (eval '(,)) (,)))
+  (assert (= (eval '{}) {}))
+  (assert (= (eval '#{}) #{})))
+
+
 (defn test-eval-globals []
   "NATIVE: test eval with explicit global dict"
   (assert (= 'bar (eval (quote foo) {'foo 'bar})))
@@ -1383,7 +1396,16 @@
 
 (defn test-read-str []
   "NATIVE: test read-str"
-  (assert (= (read-str "(print 1)") '(print 1))))
+  (assert (= (read-str "(print 1)") '(print 1)))
+  (assert (is (type (read-str "(print 1)")) (type '(print 1))))
+
+  ; Watch out for false values: https://github.com/hylang/hy/issues/1243
+  (assert (= (read-str "\"\"") '""))
+  (assert (is (type (read-str "\"\"")) (type '"")))
+  (assert (= (read-str "[]") '[]))
+  (assert (is (type (read-str "[]")) (type '[])))
+  (assert (= (read-str "0") '0))
+  (assert (is (type (read-str "0")) (type '0))))
 
 (defn test-keyword-creation []
   "NATIVE: Test keyword creation"