Export PWD and OLDPWD.

That is, the variables are not only set within the shell, but exported
to child processes.  This seems to be an undocumented feature of bash
and dash?

Found with

env -i -- $sh -c env

Tricky issue: it's hidden in spec tests with bin/osh, because bin/osh
is a shell wrapper run with dash (/bin/sh)!  It only showed up in the
tests against the release binary, where we use a symlink.

Author: Andy Chu

devtools/release.sh

@@ -1,9 +1,12 @@
 #!/bin/bash
 #
+# The big Oil release process.
+#
 # Usage:
 #   devtools/release.sh <function name>
 #
 # Pre-release:
+#   demo/osh-debug.sh osh-for-release: Start a shell to dogfood
 #   opy/regtest.sh verify-golden, because that one tends to be flaky
 #   build/cpython-defs.sh {oil-py-names,filter-methods}   # regenerate C source
 #     (BUG: this depends on build/test.sh oil-tar and building the tarball)
@@ -36,6 +39,8 @@
 #   MAYBE: ./local.sh test-release-tree if you want to preview it
 #   $0 sync-old-tar (for releases.html)
 #   $0 deploy-doc
+#
+#   demo/osh-debug.sh analyze  # see what you ran
 # 
 # - Go to oilshell.org__deploy and "git add release/$VERSION".
 # - Go to oilshell.org repo and do ./deploy.sh site.

osh/builtin.py

@@ -644,8 +644,8 @@ def Cd(argv, mem, dir_stack):
     util.error("cd %r: %s", real_dest_dir, posix.strerror(e.errno))
     return 1
 
-  state.SetGlobalString(mem, 'OLDPWD', pwd.s)
-  state.SetGlobalString(mem, 'PWD', real_dest_dir)
+  state.ExportGlobalString(mem, 'OLDPWD', pwd.s)
+  state.ExportGlobalString(mem, 'PWD', real_dest_dir)
   dir_stack.Reset()  # for pushd/popd/dirs
   return 0
 

osh/state.py

@@ -512,11 +512,14 @@ def Dump(self):
     return var_stack, argv_stack, debug_stack
 
   def _InitDefaults(self):
+    # For some reason this is one of few variables EXPORTED.  bash and dash
+    # both do it.  (e.g. env -i -- dash -c env)
+    ExportGlobalString(self, 'PWD', posix.getcwd())
+
     # Default value; user may unset it.
     # $ echo -n "$IFS" | python -c 'import sys;print repr(sys.stdin.read())'
     # ' \t\n'
     SetGlobalString(self, 'IFS', split.DEFAULT_IFS)
-    SetGlobalString(self, 'PWD', posix.getcwd())
 
     # NOTE: Should we put these in a namespace for Oil?
     SetGlobalString(self, 'UID', str(posix.getuid()))
@@ -1099,7 +1102,7 @@ def SetArrayDynamic(mem, name, a):
 
 
 def SetGlobalString(mem, name, s):
-  """Helper for completion, $PWD, etc."""
+  """Helper for completion, etc."""
   assert isinstance(s, str)
   val = value.Str(s)
   mem.SetVar(lhs_expr.LhsName(name), val, (), scope_e.GlobalOnly)
@@ -1111,6 +1114,14 @@ def SetGlobalArray(mem, name, a):
   mem.SetVar(lhs_expr.LhsName(name), value.StrArray(a), (), scope_e.GlobalOnly)
 
 
+def ExportGlobalString(mem, name, s):
+  """Helper for completion, $PWD, $OLDPWD, etc."""
+  assert isinstance(s, str)
+  val = value.Str(s)
+  mem.SetVar(lhs_expr.LhsName(name), val, (var_flags_e.Exported,),
+             scope_e.GlobalOnly)
+
+
 def GetGlobal(mem, name):
   assert isinstance(name, str), name
   return mem.GetVar(name, scope_e.GlobalOnly)

spec/builtins.test.sh

@@ -25,8 +25,17 @@ echo $PWD
 cd /
 cd $TMP
 echo "old: $OLDPWD"
+env | grep OLDPWD  # It's EXPORTED too!
 cd -
-## stdout-json: "old: /\n/\n"
+## STDOUT:
+old: /
+OLDPWD=/
+/
+## END
+## BUG mksh STDOUT:
+old: /
+/
+## END
 
 #### pwd
 cd /