dispatch: always load extensions before running shell aliases (issue5230)

dispatch: always load extensions before running shell aliases (issue5230)

Before this patch, we may or may not load extensions for shell aliases
depending on whether the command is abbreviated or not.

Loading extensions may have useful side effects to shell aliases. For example,
the pager extension does not work for shell aliases.

This patch removes the code checking shell aliases before loading extensions
to give the user a more consistent experience. It may hurt performance for
shell aliases a bit without chg but the correctness seems worth it. It will
also make the behavior consistent with chg since chg will always load all
extensions before running commands.

--- a/mercurial/dispatch.py	Mon May 09 21:13:50 2016 -0400
+++ b/mercurial/dispatch.py	Sat May 07 14:12:23 2016 +0100
@@ -670,12 +670,8 @@
 
     return path, lui
 
-def _checkshellalias(lui, ui, args, precheck=True):
-    """Return the function to run the shell alias, if it is required
-
-    'precheck' is whether this function is invoked before adding
-    aliases or not.
-    """
+def _checkshellalias(lui, ui, args):
+    """Return the function to run the shell alias, if it is required"""
     options = {}
 
     try:
@@ -686,16 +682,11 @@
     if not args:
         return
 
-    if precheck:
-        strict = True
-        cmdtable = commands.table.copy()
-        addaliases(lui, cmdtable)
-    else:
-        strict = False
-        cmdtable = commands.table
+    cmdtable = commands.table
 
     cmd = args[0]
     try:
+        strict = ui.configbool("ui", "strict")
         aliases, entry = cmdutil.findcmd(cmd, cmdtable, strict)
     except (error.AmbiguousCommand, error.UnknownCommand):
         return
@@ -745,12 +736,6 @@
     rpath = _earlygetopt(["-R", "--repository", "--repo"], args)
     path, lui = _getlocal(ui, rpath)
 
-    # Now that we're operating in the right directory/repository with
-    # the right config settings, check for shell aliases
-    shellaliasfn = _checkshellalias(lui, ui, args)
-    if shellaliasfn:
-        return shellaliasfn()
-
     # Configure extensions in phases: uisetup, extsetup, cmdtable, and
     # reposetup. Programs like TortoiseHg will call _dispatch several
     # times so we keep track of configured extensions in _loaded.
@@ -772,13 +757,11 @@
 
     addaliases(lui, commands.table)
 
-    if not lui.configbool("ui", "strict"):
-        # All aliases and commands are completely defined, now.
-        # Check abbreviation/ambiguity of shell alias again, because shell
-        # alias may cause failure of "_parse" (see issue4355)
-        shellaliasfn = _checkshellalias(lui, ui, args, precheck=False)
-        if shellaliasfn:
-            return shellaliasfn()
+    # All aliases and commands are completely defined, now.
+    # Check abbreviation/ambiguity of shell alias.
+    shellaliasfn = _checkshellalias(lui, ui, args)
+    if shellaliasfn:
+        return shellaliasfn()
 
     # check for fallback encoding
     fallback = lui.config('ui', 'fallbackencoding')

--- a/tests/test-pager.t	Mon May 09 21:13:50 2016 -0400
+++ b/tests/test-pager.t	Sat May 07 14:12:23 2016 +0100
@@ -177,3 +177,15 @@
   paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
   paged! 'summary:     modify a 8\n'
   paged! '\n'
+
+Pager works with shell aliases.
+
+  $ cat >> $HGRCPATH <<EOF
+  > [alias]
+  > echoa = !echo a
+  > EOF
+
+  $ hg echoa
+  a
+  $ hg --config pager.attend-echoa=yes echoa
+  paged! 'a\n'