[hay] Two hay evaluation modes.

- Within 'hay eval' and eval_hay(): basic sandboxing.
  - You can call procs, hay nodes, or echo/write/use.
- At the top level: there is no sandboxing.
  - You can get the result with _hay()
  - Maybe this goes within proc _main later?

The non-sandboxed kind should be useful for associating metadata with
procs?  But I guess you can't use eval_hay() on it, because that's also
sandboxed.

Might need to tweak these rules.

This is part of #951.

core/executor.py

@@ -215,15 +215,32 @@ def RunSimpleCommand(self, cmd_val, cmd_st, do_fork, call_procs=True):
           status = self.cmd_ev.RunProc(proc_node, argv[1:], arg0_spid)
         return status
 
+    # Notes:
+    # - procs shadow hay names
+    # - hay names shadow normal builtins?  Should we limit to CAPS or no?
+    if self.hay_state.Resolve(arg0):
+      return self.RunBuiltin(builtin_i.haynode, cmd_val)
+
     builtin_id = consts.LookupNormalBuiltin(arg0)
 
+    if self.exec_opts._running_hay():
+      # Hay: limit the builtins that can be run
+      # - declare 'use dialect'
+      # - echo and write for debugging
+      # - no JSON?
+      if builtin_id in (
+          builtin_i.haynode, builtin_i.use, builtin_i.echo, builtin_i.write):
+        cmd_st.show_code = True  # this is a "leaf" for errors
+        return self.RunBuiltin(builtin_id, cmd_val)
+
+      self.errfmt.Print_('Unknown command %r while running hay' % arg0,
+                         span_id=arg0_spid)
+      return 127
+
     if builtin_id != consts.NO_INDEX:
       cmd_st.show_code = True  # this is a "leaf" for errors
       return self.RunBuiltin(builtin_id, cmd_val)
 
-    if self.exec_opts._running_hay() and self.hay_state.Resolve(arg0):
-      return self.RunBuiltin(builtin_i.haynode, cmd_val)
-
     environ = self.mem.GetExported()  # Include temporary variables
 
     if cmd_val.typed_args:

core/state.py

@@ -343,7 +343,6 @@ def __init__(self):
     self.cur_defs = self.root_defs  # Same as ClearDefs()
     self.def_stack = [self.root_defs]
 
-    # same as ClearResult()
     node = self._MakeOutputNode()
     self.result_stack = [node]  # type: List[Dict[str, Any]]
     self.output = None  # type: Dict[str, Any]
@@ -357,15 +356,20 @@ def _MakeOutputNode(self):
 
   def PushEval(self):
     # type: () -> None
-    self.output = None  # clear it to make sure
+
+    # remove previous results
+    node = self._MakeOutputNode()
+    self.result_stack = [node]
+
+    self.output = None  # remove last reuslt
 
   def PopEval(self):
     # type: () -> None
 
-    # Save it
+    # Save the result
     self.output = self.result_stack[0]
 
-    # Now reset
+    # Clear results
     node = self._MakeOutputNode()
     self.result_stack = [node]
 

spec/hay.test.sh

@@ -101,32 +101,100 @@ hay eval :foo {
     echo bar
   }
 }
-## status: 1
+## status: 127
 ## STDOUT:
 foo
 ## END
 
-#### hay names only visible in 'hay eval' block
-shopt --set parse_brace
+#### hay names at top level
+shopt --set parse_brace parse_at
 shopt --unset errexit
 
-hay define package
+hay define Package
 
-package cppunit
+Package one
 echo status=$?
 
+setvar args = _hay()['children'][0]['args']
+write --sep ' ' $len(_hay()['children']) @args
+
 hay eval :result {
-  package cppunit
+  Package two
   echo status=$?
 }
 
-package cppunit
+setvar args = result['children'][0]['args']
+write --sep ' ' $len(result['children']) @args
+
+Package three
 echo status=$?
 
+setvar args = _hay()['children'][0]['args']
+write --sep ' ' $len(_hay()['children']) $[_hay()['children'][0]['args'][0]]
+
 ## STDOUT:
-status=127
 status=0
-status=127
+1 one
+status=0
+1 two
+status=0
+1 three
+## END
+
+#### builtins an externals not available in hay eval
+shopt --set parse_brace
+shopt --unset errexit
+
+hay define Package
+
+try {
+  hay eval :result {
+    Package foo {
+      /bin/ls
+    }
+  }
+}
+echo "status $_status"
+
+try {
+  hay eval :result {
+    cd /tmp
+  }
+}
+echo "status $_status"
+
+## STDOUT:
+status 127
+status 127
+## END
+
+#### procs in hay eval
+shopt --set parse_brace parse_at parse_proc
+
+hay define Package
+
+proc outside {
+  echo outside
+  Package OUT
+}
+
+hay eval :result {
+  outside
+
+  proc inside {
+    echo inside
+  }
+
+  inside
+}
+
+const args = result['children'][0]['args']
+write --sep ' ' -- $len(result['children']) @args
+
+## STDOUT:
+outside
+inside
+1 OUT
 ## END
 
 #### hay eval attr node, and JSON
@@ -420,6 +488,7 @@ foo bar
 shopt --set oil:all parse_equals
 
 hay define package
+hay define deps/package
 
 hay eval :result {
 
@@ -430,8 +499,6 @@ hay eval :result {
     echo "backup = https://archive.example.com/$URL_PATH"
   }
 
-  hay define deps/package
-
   # Note: PushTemp() happens here
   deps spam {
     # OVERRIDE

test/parse-errors.sh

@@ -745,7 +745,7 @@ oil_expr_more() {
 oil_hay_assign() {
   set +o errexit
 
-  if _is-oil-native; then
+  if is-oil-native; then
     return
   fi