[PATCH 2 of 2] alias: expand "$@" as list of parameters quoted individually (BC) (issue4200)

[Augie Fackler]

On Thu, Aug 14, 2014 at 12:02:07AM -0700, Siddharth Agarwal wrote:
> On 08/13/2014 11:54 PM, Siddharth Agarwal wrote:
> ># HG changeset patch
> ># User Siddharth Agarwal <sid0 at fb.com>
> ># Date 1407997312 25200
> >#      Wed Aug 13 23:21:52 2014 -0700
> ># Node ID 38b9b34c3351935a54a2d4da185452a753c98970
> ># Parent  c3fbbb727b54c25c93ef64a7353e62503e0fa441
> >alias: expand "$@" as list of parameters quoted individually (BC) (issue4200)
>
> If this is too risky to be accepted, we can probably introduce another magic
> character for this. For example, $%, which isn't taken by bash or zsh. It'll
> also make this patch a lot simpler.

I'm strongly in favor of $@, and folks in IRC also seemed similarly
enthusiastic. Queued.

>
> >
> >Before this patch, there was no way to pass in all the positional parameters as
> >separate words down to another command.
> >
> >(1) $@ (without quotes) would expand to all the parameters separated by a space.
> >     This would work fine for arguments without spaces, but arguments with spaces
> >     in them would be split up by POSIX shells into separate words.
> >(2) '$@' (in single quotes) would expand to all the parameters within a pair of
> >     single quotes. POSIX shells would then treat the entire list of arguments
> >     as one word.
> >(3) "$@" (in double quotes) would expand similarly to (2).
> >
> >With this patch, we expand "$@" (in double quotes) as all positional
> >parameters, quoted individually with util.shellquote, and separated by spaces.
> >Under standard field-splitting conditions, POSIX shells will tokenize each
> >argument into exactly one word.
> >
> >This is a backwards-incompatible change, but the old behavior was arguably a
> >bug: Bourne-derived shells have expanded "$@" as a tokenized list of positional
> >parameters for a very long time. I could find this behavior specified in IEEE
> >Std 1003.1-2001, and this probably goes back to much further before that.
> >
> >diff --git a/mercurial/dispatch.py b/mercurial/dispatch.py
> >--- a/mercurial/dispatch.py
> >+++ b/mercurial/dispatch.py
> >@@ -331,6 +331,27 @@
> >          args = shlex.split(cmd)
> >      return args + givenargs
> >+def aliasinterpolate(name, args, cmd):
> >+    '''interpolate args into cmd for shell aliases
> >+
> >+    This also handles $0, $@ and "$@".
> >+    '''
> >+    # util.interpolate can't deal with "$@" (with quotes) because it's only
> >+    # built to match prefix + patterns.
> >+    replacemap = dict(('$%d' % (i + 1), arg) for i, arg in enumerate(args))
> >+    replacemap['$0'] = name
> >+    replacemap['$$'] = '$'
> >+    replacemap['$@'] = ' '.join(args)
> >+    # Typical Unix shells interpolate "$@" (with quotes) as all the positional
> >+    # parameters, separated out into words. Emulate the same behavior here by
> >+    # quoting the arguments individually. POSIX shells will then typically
> >+    # tokenize each argument into exactly one word.
> >+    replacemap['"$@"'] = ' '.join(util.shellquote(arg) for arg in args)
> >+    # escape '\$' for regex
> >+    regex = '|'.join(replacemap.keys()).replace('$', r'\$')
> >+    r = re.compile(regex)
> >+    return r.sub(lambda x: replacemap[x.group()], cmd)
> >+
> >  class cmdalias(object):
> >      def __init__(self, name, definition, cmdtable):
> >          self.name = self.cmd = name
> >@@ -376,10 +397,7 @@
> >                                   % (int(m.groups()[0]), self.name))
> >                          return ''
> >                  cmd = re.sub(r'\$(\d+|\$)', _checkvar, self.definition[1:])
> >-                replace = dict((str(i + 1), arg) for i, arg in enumerate(args))
> >-                replace['0'] = self.name
> >-                replace['@'] = ' '.join(args)
> >-                cmd = util.interpolate(r'\$', replace, cmd, escape_prefix=True)
> >+                cmd = aliasinterpolate(self.name, args, cmd)
> >                  return util.system(cmd, environ=env, out=ui.fout)
> >              self.fn = fn
> >              return
> >diff --git a/mercurial/help/config.txt b/mercurial/help/config.txt
> >--- a/mercurial/help/config.txt
> >+++ b/mercurial/help/config.txt
> >@@ -229,8 +229,9 @@
> >  Positional arguments like ``$1``, ``$2``, etc. in the alias definition
> >  expand to the command arguments. Unmatched arguments are
> >  removed. ``$0`` expands to the alias name and ``$@`` expands to all
> >-arguments separated by a space. These expansions happen before the
> >-command is passed to the shell.
> >+arguments separated by a space. ``"$@"`` (with quotes) expands to all
> >+arguments quoted individually and separated by a space. These expansions
> >+happen before the command is passed to the shell.
> >  Shell aliases are executed in an environment where ``$HG`` expands to
> >  the path of the Mercurial that was used to execute the alias. This is
> >diff --git a/tests/test-alias.t b/tests/test-alias.t
> >--- a/tests/test-alias.t
> >+++ b/tests/test-alias.t
> >@@ -30,6 +30,7 @@
> >    > echo1 = !printf '\$1\n'
> >    > echo2 = !printf '\$2\n'
> >    > echo13 = !printf '\$1 \$3\n'
> >+  > echotokens = !printf "%s\n" "\$@"
> >    > count = !hg log -r "\$@" --template=. | wc -c | sed -e 's/ //g'
> >    > mcount = !hg log \$@ --template=. | wc -c | sed -e 's/ //g'
> >    > rt = root
> >@@ -241,6 +242,22 @@
> >    foo baz
> >    $ hg echo2 foo
> >+  $ hg echotokens
> >+
> >+  $ hg echotokens foo 'bar $1 baz'
> >+  foo
> >+  bar $1 baz
> >+  $ hg echotokens 'test $2' foo
> >+  test $2
> >+  foo
> >+  $ hg echotokens 'test $@' foo '$@'
> >+  test $@
> >+  foo
> >+  $@
> >+  $ hg echotokens 'test "$@"' foo '"$@"'
> >+  test "$@"
> >+  foo
> >+  "$@"
> >    $ echo bar > bar
> >    $ hg commit -qA -m bar
> >    $ hg count .
> >_______________________________________________
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