[FYI] {micro} tests: make script 'shell-no-trail-bslash' simpler and more robust

This solves spurious failure in the 'check-no-trailing-backslash-in-recipes'
target for Automake-NG.

This is basically a backport of Automake-NG commit v1.14.1-1010-g85aae58;
the point is to minimize the amount of spurious diffs between the mainline
Automake and the Automake-NG source trees.

* t/ax/shell-no-trail-bslash.in: Simplify and fortify.
* t/self-check-shell-no-trail-bslash.sh: Enhance.

Signed-off-by: Stefano Lattarini <[email protected]>
---
 t/ax/shell-no-trail-bslash.in         | 102 +++++++++++++++++-----------------
 t/self-check-shell-no-trail-bslash.sh |  34 +++++++++++-
 2 files changed, 83 insertions(+), 53 deletions(-)

diff --git a/t/ax/shell-no-trail-bslash.in b/t/ax/shell-no-trail-bslash.in
index f785de8..3224958 100644
--- a/t/ax/shell-no-trail-bslash.in
+++ b/t/ax/shell-no-trail-bslash.in
@@ -1,5 +1,5 @@
 #! @AM_TEST_RUNNER_SHELL@
-# Copyright (C) 2012-2013 Free Software Foundation, Inc.
+# Copyright (C) 2012-2014 Free Software Foundation, Inc.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -14,63 +14,63 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-# A "shell" that chokes on '-c' commands having a trailing '\' character
-# (possibly followed by whitespace only).  This is to emulate problems
-# seen in older bash versions (e.g., bash 2.05b).
-# See also automake bug#10436.
+# A "shell" that chokes on '-c' commands and/or shell scripts having
+# a trailing '\' character (possibly followed by whitespace only).
+# This is to emulate problems seen in older bash versions (e.g., bash
+# 2.05b). See also automake bug#10436.
 
-set -e
 set -u
 
 am_SHELL=${AM_TESTSUITE_SHELL-'@SHELL@'}
 
-tab='	'
-nl='
+(
+  set -e
+  shell_command=; unset shell_command
+  while test $# -gt 0; do
+    case $1 in
+      # The shell might be invoked by make e.g. as "sh -ec" or "sh -ce".
+      # Be liberal (in the spirit of defensive programming) and accept
+      # both forms.
+      -*c*) shell_command=$2; shift;;
+       -?*) ;;
+         *) break;;
+    esac
+    shift
+  done
+
+  if test x${shell_command+"set"} != x"set"; then
+    if test $# -gt 0; then
+      shell_command=$(cat "$1")
+    else
+      # Some make implementations, like *BSD's, pass the recipes to the
+      # shell through its standard input.  Trying to run our extra checks
+      # in this case would be too tricky, so we just skip them.
+      exit 0
+    fi
+  fi
+
+  tab='	'
+  nl='
 '
-am_shell_flags=
-am_shell_command=; unset am_shell_command
-while test $# -gt 0; do
-  case $1 in
-    # If the shell is invoked by make e.g. as "sh -ec" (seen on
-    # GNU make in POSIX mode) or "sh -ce" (seen on Solaris make).
-    -*c*)
-        am_flg=$(printf '%s\n' "$1" | sed -e 's/^-//' -e 's/c//g')
-        if test x"$am_flg" != x; then
-          am_shell_flags="$am_shell_flags -$am_flg"
-        fi
-        am_shell_command=$2
-        shift;;
-    -?*)
-        am_shell_flags="$am_shell_flags $1";;
-      *)
-        break;;
+  case "$shell_command" in
+    *" "|*"$tab"|*"$nl")
+      shell_command=$(printf '%s\n' "$shell_command" | tr -d " $tab$nl");;
   esac
-  shift
-done
-
-if test x${am_shell_command+"set"} != x"set"; then
-  # Some make implementations, like *BSD's, pass the recipes to the shell
-  # through its standard input.  Trying to run our extra checks in this
-  # case would be too tricky, so we just skip them.
-  exec $am_SHELL $am_shell_flags ${1+"$@"}
-fi
 
-case $am_shell_command in
-  *" "|*"$tab"|*"$nl")
-    am_tweaked_shell_command=$(printf '%s\n' "$am_shell_command" \
-                                 | tr -d " $tab$nl");;
-  *)
-    am_tweaked_shell_command=$am_shell_command;;
-esac
+  case "$shell_command" in
+    *\\)
+      printf '%s\n' "$0: recipe/script ends with backslash character" >&2
+      printf '%s\n' "=== BEGIN recipe/script" >&2
+      printf '%s\n' "${am_shell_command-}" >&2
+      printf '%s\n' "=== END recipe/script" >&2
+      exit 1
+      ;;
+  esac
+)
 
-case $am_tweaked_shell_command in
-  *\\)
-    printf '%s\n' "$0: recipe ends with backslash character" >&2
-    printf '%s\n' "=== BEGIN recipe" >&2
-    printf '%s\n' "${am_shell_command-}" >&2
-    printf '%s\n' "=== END recipe" >&2
-    exit 1
-    ;;
-esac
+if test $? -gt 0; then
+  # Some of our scripts or makefile recipes had invalid contents.
+  exit 3
+fi
 
-exec $am_SHELL $am_shell_flags -c "$am_shell_command" ${1+"$@"}
+exec ${AM_TESTSUITE_SHELL-'@SHELL@'} ${1+"$@"}
diff --git a/t/self-check-shell-no-trail-bslash.sh b/t/self-check-shell-no-trail-bslash.sh
index 14ee02c..1919889 100644
--- a/t/self-check-shell-no-trail-bslash.sh
+++ b/t/self-check-shell-no-trail-bslash.sh
@@ -1,5 +1,5 @@
 #! /bin/sh
-# Copyright (C) 2012-2013 Free Software Foundation, Inc.
+# Copyright (C) 2012-2014 Free Software Foundation, Inc.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -34,12 +34,42 @@ bad:
 END
 
 SHELL=$am_testaux_builddir/shell-no-trail-bslash
+
 $SHELL -c 'exit 0'
 test "$($SHELL -c 'echo is  o\k')" = "is ok"
 
+echo 'echo is  ok\"' > ok.sh
+$SHELL ./ok.sh
+test "$($SHELL ./ok.sh)" = "is ok\""
+
+tab='	'
+nl='
+'
+for sfx in \
+  '\' \
+  '\\' \
+  '\\\\\' \
+  '\ ' \
+  "\\$tab" \
+  "\\ $tab$tab   " \
+  "\\$nl" \
+  "\\ $nl " \
+  "\\$nl$nl$nl" \
+; do
+  for pfx in "" "echo bad" ": a${nl}# multine${nl}: text"; do
+    cmd=${pfx}${sfx}
+    printf '%s\n' "$cmd" > bad.sh
+    for args in '-c "$cmd"' './bad.sh'; do
+      eval "\$SHELL $args 2>stderr && { cat stderr >&2; exit 1; }; :"
+      cat stderr >&2
+      $FGREP "recipe/script ends with backslash character" stderr
+    done
+  done
+done
+
 $MAKE good
 
 run_make -E -e FAIL bad SHELL="$SHELL"
-$FGREP "recipe ends with backslash character" stderr
+$FGREP "recipe/script ends with backslash character" stderr
 
 :
-- 
2.1.3