[PATCH 1 of 2] dispatch: defer environment variable resolution in alias commands (BC)

[Jun Wu]

# HG changeset patch
# User Jun Wu <quark at fb.com>
# Date 1462576618 -3600
#      Sat May 07 00:16:58 2016 +0100
# Node ID 24dc9e5deec415bfa635fb80c7767ef5146c2775
# Parent  b473b7bd02b3bad724c0178ec08ae49019aed51c
dispatch: defer environment variable resolution in alias commands (BC)

Before this patch, if there are environment variables in an alias command,
they will be expanded immediately when we first see the alias.

This will cause issues with chg, because environment variable updates will
not propagate to expanded arguments.

This patch makes "args" of "cmdalias" a property that will be calculated
every time when accessed.

diff --git a/mercurial/dispatch.py b/mercurial/dispatch.py
--- a/mercurial/dispatch.py
+++ b/mercurial/dispatch.py
@@ -384,7 +384,7 @@
         self.cmdname = ''
         self.definition = definition
         self.fn = None
-        self.args = []
+        self.givenargs = []
         self.opts = []
         self.help = ''
         self.badalias = None
@@ -432,7 +432,7 @@
                              % (self.name, inst))
             return
         self.cmdname = cmd = args.pop(0)
-        args = map(util.expandpath, args)
+        self.givenargs = args
 
         for invalidarg in ("--cwd", "-R", "--repository", "--repo", "--config"):
             if _earlygetopt([invalidarg], args):
@@ -448,7 +448,6 @@
             else:
                 self.fn, self.opts = tableentry
 
-            self.args = aliasargs(self.fn, args)
             if self.help.startswith("hg " + cmd):
                 # drop prefix in old-style help lines so hg shows the alias
                 self.help = self.help[4 + len(cmd):]
@@ -462,6 +461,11 @@
             self.badalias = (_("alias '%s' resolves to ambiguous command '%s'")
                              % (self.name, cmd))
 
+    @property
+    def args(self):
+        args = map(util.expandpath, self.givenargs)
+        return aliasargs(self.fn, args)
+
     def __getattr__(self, name):
         adefaults = {'norepo': True, 'optionalrepo': False, 'inferrepo': False}
         if name not in adefaults:
diff --git a/tests/test-alias.t b/tests/test-alias.t
--- a/tests/test-alias.t
+++ b/tests/test-alias.t
@@ -525,6 +525,24 @@
   (use "hg help" for the full list of commands or "hg -v" for details)
   [255]
 
+environment variable changes in alias commands
+
+  $ cat > $TESTTMP/setcount.py <<EOF
+  > import os
+  > def uisetup(ui):
+  >     os.environ['COUNT'] = '2'
+  > EOF
+
+  $ cat >> $HGRCPATH <<'EOF'
+  > [extensions]
+  > setcount = $TESTTMP/setcount.py
+  > [alias]
+  > showcount = log -T "$COUNT\n" -r .
+  > EOF
+
+  $ COUNT=1 hg showcount
+  2
+
 This should show id:
 
   $ hg --config alias.log='id' log