Merge pull request #3155 from xonsh/stderr-pre

fixed XONSH_STDERR_POSTFIX issue

news/stderr-pre.rst

@@ -0,0 +1,24 @@
+**Added:**
+
+* <news item>
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* Fixed issue where setting ``$XONSH_STDERR_PREFIX`` and ``$XONSH_STDERR_POSTFIX``
+  and running a command in the ``xonshrc`` file would throw an error.
+
+**Security:**
+
+* <news item>

xonsh/tools.py

@@ -1948,16 +1948,27 @@ def format_std_prepost(template, env=None):
     if not template:
         return ""
     env = builtins.__xonsh__.env if env is None else env
-    shell = builtins.__xonsh__.shell.shell
-    try:
-        s = shell.prompt_formatter(template)
-    except Exception:
-        print_exception()
-    # \001\002 is there to fool pygments into not returning an empty string
-    # for potentially empty input. This happens when the template is just a
-    # color code with no visible text.
     invis = "\001\002"
-    s = shell.format_color(invis + s + invis, force_string=True)
+    if builtins.__xonsh__.shell is None:
+        # shell hasn't fully started up (probably still in xonshrc)
+        from xonsh.prompt.base import PromptFormatter
+        from xonsh.ansi_colors import ansi_partial_color_format
+
+        pf = PromptFormatter()
+        s = pf(template)
+        style = env.get("XONSH_COLOR_STYLE")
+        s = ansi_partial_color_format(invis + s + invis, hide=False, style=style)
+    else:
+        # shell has fully started. do the normal thing
+        shell = builtins.__xonsh__.shell.shell
+        try:
+            s = shell.prompt_formatter(template)
+        except Exception:
+            print_exception()
+        # \001\002 is there to fool pygments into not returning an empty string
+        # for potentially empty input. This happens when the template is just a
+        # color code with no visible text.
+        s = shell.format_color(invis + s + invis, force_string=True)
     s = s.replace(invis, "")
     return s