[word_eval] Fix bugs in ${var@a} implementation.

Addresses issue #690.

Also fix translation of bin/osh_eval.

mycpp/cppgen_pass.py

@@ -1661,7 +1661,7 @@ def visit_func_def(self, o: 'mypy.nodes.FuncDef') -> T:
             class_name == 'BoolEvaluator' and func_name in ('_EvalCompoundWord', '_StringToIntegerOrError') or
             class_name == 'CommandEvaluator' and func_name == '_Execute' or
             class_name is None and func_name == '_PackFlags' or
-            class_name == 'Mem' and func_name in ('GetVar', 'SetVar') or
+            class_name == 'Mem' and func_name in ('GetVar', 'SetVar', 'GetCell') or
             class_name == 'SearchPath' and func_name == 'Lookup' or
             # osh/sh_expr_eval.py
             class_name is None and func_name == 'EvalLhsAndLookup' or
@@ -2022,6 +2022,7 @@ def visit_import_from(self, o: 'mypy.nodes.ImportFrom') -> T:
                 'part_value_e', 'part_value',
                 'cmd_value_e', 'cmd_value',
                 'redirect_arg_e', 'redirect_arg',
+                'a_index_e', 'a_index',
                 ):
                 is_namespace = True
 

osh/word_eval.py

@@ -855,7 +855,6 @@ def _EvalBracedVarSub(self, part, part_vals, quoted):
       if (part.prefix_op is not None and 
           part.suffix_op is not None and
           part.suffix_op.tag_() == suffix_op_e.Nullary):
-        var_name = None
 
         names = self.mem.VarNamesStartingWith(part.token.val)
         names.sort()
@@ -972,7 +971,13 @@ def _EvalBracedVarSub(self, part, part_vals, quoted):
     else:  # no bracket op
       # When the array is "$@", var_name is None
       if var_name and val.tag_() in (value_e.MaybeStrArray, value_e.AssocArray):
-        if var_name in _STRING_AND_ARRAY:
+        suffix_op2 = part.suffix_op
+        if (suffix_op2 and suffix_op2.tag_() == suffix_op_e.Nullary and 
+            cast(Token, suffix_op2).id == Id.VOp0_a):
+          # ${array@a} is a string
+          # TODO: An IR for ${} might simplify these lengthy conditions
+          pass
+        elif var_name in _STRING_AND_ARRAY:
           bash_array_compat = True
         else:
           e_die("Array %r can't be referred to as a scalar (without @ or *)",
@@ -1001,20 +1006,33 @@ def _EvalBracedVarSub(self, part, part_vals, quoted):
             # readline gets rid of these, so we should too.
             p = prompt.replace('\x01', '').replace('\x02', '')
             val = value.Str(p)
+
           elif op_id == Id.VOp0_Q:
             assert val.tag_() == value_e.Str, val
             val = cast(value__Str, val)
             val = value.Str(string_ops.ShellQuote(val.s))
+
           elif op_id == Id.VOp0_a:
             # We're ONLY simluating -a and -A, not -r -x -n for now.  See
             # spec/ble-idioms.test.sh.
-            s = ''
+            chars = []  # type: List[str]
             with tagswitch(val) as case:
               if case(value_e.MaybeStrArray):
-                s += 'a'
+                chars.append('a')
               elif case(value_e.AssocArray):
-                s += 'A'
-            val = value.Str(s)
+                chars.append('A')
+
+            if var_name is not None:  # e.g. ${?@a} is allowed
+              cell = self.mem.GetCell(var_name)
+              if cell.readonly:
+                chars.append('r')
+              if cell.exported:
+                chars.append('x')
+              if cell.nameref:
+                chars.append('n')
+
+            val = value.Str(''.join(chars))
+
           else:
             e_die('Var op %r not implemented', op.val, token=op)
 

spec/var-op-bash.test.sh

@@ -90,3 +90,26 @@ echo ${!hello@}
 hello1 hello2 hello3
 hello hello1 hello2 hello3
 ## END
+
+#### ${var@a} for attributes
+array=(one two)
+echo ${array@a}
+declare -r array=(one two)
+echo ${array@a}
+declare -rx PYTHONPATH=hi
+echo ${PYTHONPATH@a}
+
+# bash and osh differ here
+#declare -rxn x=z
+#echo ${x@a}
+## STDOUT:
+a
+ar
+rx
+## END
+
+#### ${var@a} error conditions
+echo [${?@a}]
+## STDOUT:
+[]
+## END