patch 9.0.0648: when using powershell input redirection does not work

Problem:    When using powershell input redirection does not work.
Solution:   Use a different shell command for powershell. (Yegappan
            Lakshmanan, closes #11257)

src/ex_cmds.c

@@ -1531,35 +1531,61 @@ make_filter_cmd(
 {
     char_u	*buf;
     long_u	len;
-
+    int		is_powershell = FALSE;
-#if defined(UNIX)
+#ifdef UNIX
     int		is_fish_shell;
-    char_u	*shell_name = get_isolated_shell_name();
+#endif
 
+    char_u *shell_name = get_isolated_shell_name();
     if (shell_name == NULL)
 	return NULL;
 
+#if defined(UNIX)
     // Account for fish's different syntax for subshells
-    is_fish_shell = (fnamecmp(shell_name, "fish") == 0);
+    is_fish_shell = fnamecmp(shell_name, "fish") == 0;
-    vim_free(shell_name);
     if (is_fish_shell)
 	len = (long_u)STRLEN(cmd) + 13;		// "begin; " + "; end" + NUL
     else
 #endif
+    {
+	is_powershell = (shell_name[0] == 'p')
+			&& (fnamecmp(shell_name, "powershell") == 0
+				|| fnamecmp(shell_name, "powershell.exe") == 0
+				|| fnamecmp(shell_name, "pwsh") == 0
+				|| fnamecmp(shell_name, "pwsh.exe") == 0);
 	len = (long_u)STRLEN(cmd) + 3;		// "()" + NUL
+    }
+
     if (itmp != NULL)
+    {
+	if (is_powershell)
+	    // "& { Get-Content " + " | & " + " }"
+	    len += (long_u)STRLEN(itmp) + 24;
+	else
 	    len += (long_u)STRLEN(itmp) + 9;	// " { < " + " } "
+    }
     if (otmp != NULL)
 	len += (long_u)STRLEN(otmp) + (long_u)STRLEN(p_srr) + 2; // "  "
+
+    vim_free(shell_name);
+
     buf = alloc(len);
     if (buf == NULL)
 	return NULL;
 
+    if (is_powershell)
+    {
+	if (itmp != NULL)
+	    vim_snprintf((char *)buf, len, "& { Get-Content %s | & %s }",
+								itmp, cmd);
+	else
+	    vim_snprintf((char *)buf, len, "(%s)", cmd);
+    }
+    else
+    {
 #if defined(UNIX)
-    /*
+	// Put braces around the command (for concatenated commands) when
-     * Put braces around the command (for concatenated commands) when
+	// redirecting input and/or output.
-     * redirecting input and/or output.
-     */
 	if (itmp != NULL || otmp != NULL)
 	{
 	    if (is_fish_shell)
@@ -1575,8 +1601,8 @@ make_filter_cmd(
 	    STRCAT(buf, itmp);
 	}
 #else
-    // For shells that don't understand braces around commands, at least allow
+	// For shells that don't understand braces around commands, at least
-    // the use of commands in a pipe.
+	// allow the use of commands in a pipe.
 	if (*p_sxe != NUL && *p_sxq == '(')
 	{
 	    if (itmp != NULL || otmp != NULL)
@@ -1612,13 +1638,15 @@ make_filter_cmd(
 		    p = find_pipe(cmd);
 		    if (p != NULL)
 		    {
-		    STRCAT(buf, " ");  // insert a space before the '|' for DOS
+			// insert a space before the '|' for DOS
+			STRCAT(buf, " ");
 			STRCAT(buf, p);
 		    }
 		}
 	    }
 	}
 #endif
+    }
     if (otmp != NULL)
 	append_redir(buf, (int)len, p_srr, otmp);
 

src/testdir/test_shell.vim

@@ -97,6 +97,18 @@ func Test_shell_options()
       finally
         bwipe!
       endtry
+
+      " filter buffer contents through an external command
+      new
+      call setline(1, ['tom', 'sam', 'andy'])
+      try
+        %!sort
+        call assert_equal(['andy', 'sam', 'tom'], getline(1, '$'), e[0])
+      catch
+        call assert_report($'Failed to filter buffer contents, shell: {e[0]}, caught {v:exception}')
+      finally
+        bwipe!
+      endtry
     endif
   endfor
   set shell& shellcmdflag& shellpipe& shellquote&

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    648,
 /**/
     647,
 /**/