Re: [PATCH] Support the mksh's ${|func;} substitution

[Sebastian Gniazdowski <sgniazdowski@gmail.com>]

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On Sat, 7 Sep 2019 at 22:19, Stephane Chazelas
<stephane.chazelas@gmail.com> wrote:
>
> 2019-09-07 20:09:57 +0200, Sebastian Gniazdowski:
> > The parsing would have to be changed to prevent the "=" in function names?
> [...]
>
> No, I meant that you'd need the parser to handle that case of a
> pseudo-command group  (a {any shell code here} but with {|
> instead of {)).
>
> So you can do:
>
> echo ${|
>   whatever $(...)
>   for i do
>     ...
>   done}
>
> Whether it would actually be difficult or not I can't comment,
> I've not looked at the parser code.

I think that it's already supported with the single exception that }
would have to be quoted:

% print ${|
  whatever $(...)
  for i do
    ...
  done;}
zsh: no such function: \n  whatever $(...)\n  for i do\n    ...\n  done

> Having an operator that *only* invokes a function to do an
> expansion is less useful IMO. That just sound like a very
> limited form of command substitution where you could have done a
> more complete form by allowing any code instead of just one
> function invocation without argument.

Ok, I agree, the lambda-function reminiscent version is better. It
also isn't much harder to implement – instead of the doshfunc() just
bin_eval() would have to be called. I attach such patch. However, it
has some problems:

arr=( val1 val2 abc1 abc3 )
print ${arr[@]//(#b)(*)/${|REPLY\=test;}}
Output:test test test test

So the = has to be quoted. Also, not much more works. REPLY\=$MATCH
nor REPLY\=\$MATCH are working. I wonder why, as it doesn't look that
bad in general:

whatever() { echo func ran; }
echo ${|
  whatever $(...)
  for i in a b c; do
    REPLY\=1
  done;}

Output:
func ran
1

-- 
Sebastian Gniazdowski
News: https://twitter.com/ZdharmaI
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Blog: http://zdharma.org

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From 6c4a2b778ca4c625bf15cf700d6ec3ce1aea1bcf Mon Sep 17 00:00:00 2001
From: Sebastian Gniazdowski <sgniazdowski@gmail.com>
Date: Fri, 6 Sep 2019 02:35:14 +0200
Subject: [PATCH] Support the mksh's substitution ${|func;}

---
 Src/subst.c | 46 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 45 insertions(+), 1 deletion(-)

diff --git a/Src/subst.c b/Src/subst.c
index b132f251b..dc2b58cc7 100644
--- a/Src/subst.c
+++ b/Src/subst.c
@@ -29,6 +29,7 @@
 
 #include "zsh.mdh"
 #include "subst.pro"
+#include "builtin.pro"
 
 #define LF_ARRAY	1
 
@@ -1847,8 +1848,17 @@ paramsubst(LinkList l, LinkNode n, char **str, int qt, int pf_flags,
      * nested (P) flags.
      */
     int fetch_needed;
+    /* Indicates ${|func;} */
+    int rplyfunc = 0;
+    /* The name of the function to be ran by ${|...;} */
+    char *rplycode[2] = {NULL, NULL};
+    /* The length of the input string */
+    int slen = 0;
+    /* The closing brace pointer */
+    char *outbracep;
 
     *s++ = '\0';
+    slen = strlen(s);
     /*
      * Nothing to do unless the character following the $ is
      * something we recognise.
@@ -1876,6 +1886,36 @@ paramsubst(LinkList l, LinkNode n, char **str, int qt, int pf_flags,
     if (c == Inbrace) {
 	inbrace = 1;
 	s++;
+
+        /* Short-path for the function-running substitution ${|func;}
+         * The function name is extracted and called, and the
+         * substitution assigned. There's no (...)-flags processing,
+         * i.e. no ${|(U)func;}, because it looks quite awful and
+         * also requires a change to the manual, part about the
+         * substitution order. Use ${(U)${|func;}} instead, it looks
+         * cleaner. */
+        if ( ((outbracep=strchr(s,Outbrace)) ||
+             (outbracep=strchr(s,'}'))) &&
+                (s[0] == Bar || s[0] == '|') &&
+                    outbracep[-1] == ';' )
+        {
+            rplyfunc = 1;
+            rplycode[0] = dupstrpfx(s+1, outbracep-s-2);
+            s=outbracep;
+
+            /* Execute the shell function */
+            bin_eval(NULL, rplycode, NULL, 0);
+
+            val = getsparam("REPLY");
+            if (val)
+                vunset = 0;
+            else {
+                vunset = 1;
+                val = dupstring("");
+            }
+            fetch_needed = 0;
+        }
+
 	/*
 	 * In ksh emulation a leading `!' is a special flag working
 	 * sort of like our (k).
@@ -2519,7 +2559,11 @@ paramsubst(LinkList l, LinkNode n, char **str, int qt, int pf_flags,
 			     scanflags)) ||
 	    (v->pm && (v->pm->node.flags & PM_UNSET)) ||
 	    (v->flags & VALFLAG_EMPTY))
-	    vunset = 1;
+        {
+            if (!rplyfunc) {
+                vunset = 1;
+            }
+        }
 
 	if (wantt) {
 	    /*
-- 
2.21.0