Fix AST representation of format strings

NEWS.rst

@@ -20,6 +20,7 @@ Bug Fixes
 ------------------------------
 * Statements in the second argument of `assert` are now executed.
 * Fixed the expression of a while loop that contains statements being compiled twice.
+* `hy2py` can now handle format strings.
 
 0.17.0
 ==============================

hy/compiler.py

@@ -1784,7 +1784,7 @@ class HyASTCompiler(object):
                item = item[2:].lstrip()
 
            # Look for a format specifier.
-           format_spec = asty.Str(string, s = "")
+           format_spec = None
            if item.startswith(':'):
                if allow_recursion:
                    ret += self._format_string(string,
@@ -1793,6 +1793,8 @@ class HyASTCompiler(object):
                    format_spec = ret.force_expr
                else:
                    format_spec = asty.Str(string, s=item[1:])
+                   if PY36:
+                       format_spec = asty.JoinedStr(string, values=[format_spec])
            elif item:
                raise self._syntax_error(string,
                    "f-string: trailing junk in field")
@@ -1818,7 +1820,9 @@ class HyASTCompiler(object):
                            ('!' + conversion if conversion else '') +
                            ':{}}'),
                        attr = 'format', ctx = ast.Load()),
-                   args = [ret.force_expr, format_spec],
+                   args = [
+                       ret.force_expr,
+                       format_spec or asty.Str(string, s = "")],
                    keywords = [], starargs = None, kwargs = None))
 
         return ret + (

tests/resources/pydemo.hy

@@ -49,6 +49,10 @@ Call me Ishmael. Some years ago—never mind how long precisely—having little
 (setv condexpr (if "" "x" "y"))
 (setv mylambda (fn [x] (+ x "z")))
 
+(setv fstring1 f"hello {(+ 1 1)} world")
+(setv p "xyzzy")
+(setv fstring2 f"a{p !r :9}")
+
 (setv augassign 103)
 (//= augassign 4)
 

tests/test_hy2py.py

@@ -79,6 +79,9 @@ def assert_stuff(m):
     assert type(m.mylambda) is type(lambda x: x + "z")
     assert m.mylambda("a") == "az"
 
+    assert m.fstring1 == "hello 2 world"
+    assert m.fstring2 == "a'xyzzy'  "
+
     assert m.augassign == 25
 
     assert m.delstatement == ["a", "c", "d", "e"]