[Libguestfs] [libnbd PATCH] nbdsh: Add -b option to simplify h.block_status

[Eric Blake]

We decided to not request the "base:allocation" context by default (if
a client wants to use block_status on a different context, then they'd
have to get any default request out of the way); however, block status
is useless without at least one meta context.  This adds a convenience
knob for requesting that, and has the nice benefit of working with the
--connect command line option (previously, if you wanted to use
block_status, you could not use --connect, because requesting the meta
context must happen before the connection).
---
 sh/nbdsh.pod       |  9 +++++++
 python/nbdsh.py    |  4 +++
 sh/Makefile.am     |  4 ++-
 sh/test-context.sh | 62 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 78 insertions(+), 1 deletion(-)
 create mode 100755 sh/test-context.sh

diff --git a/sh/nbdsh.pod b/sh/nbdsh.pod
index d7fc315..6c540c7 100644
--- a/sh/nbdsh.pod
+++ b/sh/nbdsh.pod
@@ -56,6 +56,15 @@ __EXAMPLES_HEXDUMP__

 Display brief command line help and exit.

+=item B<-b>
+
+=item B<--base-allocation>
+
+Request the use of the "base:allocation" meta context, which is the
+most common context used with L<nbd_block_status(3)>.  This is
+equivalent to calling S<C<h.set_meta_context
+(nbd.CONTEXT_BASE_ALLOCATION)>> in the shell prior to connecting.
+
 =item B<-c> 'COMMAND ...'

 =item B<--command> 'COMMAND ...'
diff --git a/python/nbdsh.py b/python/nbdsh.py
index 319b0f0..00bc6bc 100644
--- a/python/nbdsh.py
+++ b/python/nbdsh.py
@@ -27,6 +27,8 @@ def shell():
     epilog = '''Please read the nbdsh(1) manual page for full usage.'''
     parser = argparse.ArgumentParser (prog='nbdsh', description=description,
                                       epilog=epilog)
+    parser.add_argument ('-b', '--base-allocation', action='store_true',
+                         help='request the "base:allocation" meta context')
     parser.add_argument ('--connect', metavar='URI',
                          help="connect to NBD URI")
     parser.add_argument ('-c', '--command', action='append',
@@ -52,6 +54,8 @@ exit() or Ctrl-D                    # Quit the shell
 help (nbd)                          # Display documentation
 '''

+    if args.base_allocation:
+        h.add_meta_context (nbd.CONTEXT_BASE_ALLOCATION)
     if args.connect is not None:
         h.connect_uri (args.connect)
     # If there are no -c or --command parameters, go interactive,
diff --git a/sh/Makefile.am b/sh/Makefile.am
index 8f70e69..415e241 100644
--- a/sh/Makefile.am
+++ b/sh/Makefile.am
@@ -21,6 +21,7 @@ EXTRA_DIST = \
 	nbdsh.pod \
 	examples/LICENSE-FOR-EXAMPLES \
 	examples/hexdump.sh \
+	test-context.sh \
 	test-help.sh \
 	test-pattern.sh \
 	test-version.sh \
@@ -43,7 +44,7 @@ nbdsh.1: nbdsh.pod $(top_builddir)/podwrapper.pl

 endif HAVE_POD

-TESTS_ENVIRONMENT = LIBNBD_DEBUG=1 EXP_VERSION=$(VERSION)
+TESTS_ENVIRONMENT = LIBNBD_DEBUG=1 NBDKIT_DEBUG=1 EXP_VERSION=$(VERSION)
 LOG_COMPILER = $(top_builddir)/run
 TESTS = \
 	test-help.sh \
@@ -53,6 +54,7 @@ TESTS = \
 if HAVE_NBDKIT

 TESTS += \
+	test-context.sh \
 	test-pattern.sh \
 	$(NULL)

diff --git a/sh/test-context.sh b/sh/test-context.sh
new file mode 100755
index 0000000..55f9b53
--- /dev/null
+++ b/sh/test-context.sh
@@ -0,0 +1,62 @@
+#!/usr/bin/env bash
+# nbd client library in userspace
+# Copyright (C) 2019 Red Hat Inc.
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+# Test effects of nbdsh -b
+fail=0
+
+# Without -b, no meta context is requested
+output=$(nbdkit -U - null --run 'nbdsh \
+    --connect "nbd+unix://?socket=$unixsocket" \
+    -c "print (h.can_meta_context (nbd.CONTEXT_BASE_ALLOCATION))" </dev/null')
+if test "x$output" != xFalse; then
+    echo "$0: unexpected output: $output"
+    fail=1
+fi
+
+# With -b (and a server that supports it), meta context works.
+output=$(nbdkit -U - null --run 'nbdsh \
+    -b --connect "nbd+unix://?socket=$unixsocket" \
+    -c "print (h.can_meta_context (nbd.CONTEXT_BASE_ALLOCATION))" </dev/null')
+if test "x$output" != xTrue; then
+    echo "$0: unexpected output: $output"
+    fail=1
+fi
+
+# Again, but with -b after --connect
+output=$(nbdkit -U - null --run 'nbdsh \
+    --connect "nbd+unix://?socket=$unixsocket" --base-allocation \
+    -c "print (h.can_meta_context (nbd.CONTEXT_BASE_ALLOCATION))" </dev/null')
+if test "x$output" != xTrue; then
+    echo "$0: unexpected output: $output"
+    fail=1
+fi
+
+if [[ $(nbdkit --help) =~ --no-sr ]]; then
+    # meta context depends on server cooperation
+    output=$(nbdkit -U - --no-sr null --run 'nbdsh \
+      --connect "nbd+unix://?socket=$unixsocket" --base-allocation \
+      -c "print (h.can_meta_context (nbd.CONTEXT_BASE_ALLOCATION))" </dev/null')
+    if test "x$output" != xFalse; then
+        echo "$0: unexpected output: $output"
+        fail=1
+    fi
+else
+    echo "$0: nbdkit lacks --no-sr"
+fi
+
+exit $fail
-- 
2.21.0