Dear Maintainer,

I ran mk-build-deps in a directory in which the user running it has no
write permissions. An error message is displayed, but the program exits
with a zero exit code but was not able to perform its duty:

$ mk-build-deps
Error in tempdir() using /tmp/localdir/equivs.XXXXXX: Could not create directory /tmp/localdir/equivs.DB5LRY: Permission denied at /usr/bin/equivs-build line 19.

$ echo $?
0

I expect the program to return anything else but 0 so that programs
relying on exit code will work.

As a workaround in my build scripts, I now check if mk-build-deps
created any *deb files

Best
Andreas Steinel
--- /etc/devscripts.conf ---

--- ~/.devscripts ---
Not present

I ran mk-build-deps in a packaging directory with a B-D list roughly converted
from language specific manifest, which resulted in some errors.
dpkg-checkbuilddeps correctly identified the error and properly failed:

----
root@devoid /w/t/trippy (debian/sid)# dpkg-checkbuilddeps
dpkg-checkbuilddeps: warning: can't parse dependency librust-insta = (1.39.0)
dpkg-checkbuilddeps: error: cannot parse Build-Depends/Build-Depends-Arch/Build-Depends-Indep field
root@devoid /w/t/trippy (debian/sid) [255]#
----

(Don't mind the root user, it's in a container.)

But mk-build-deps happily continues, producing an empty .deb, only showing a
warning at the very top:

----
root@devoid /w/t/trippy (debian/sid)# mk-build-deps
mk-build-deps: warning: can't parse dependency librust-insta = (1.39.0)
Use of uninitialized value $positive in concatenation (.) or string at /usr/bin/mk-build-deps line 581.
dpkg-buildpackage: info: source package rust-trippy-build-deps
dpkg-buildpackage: info: source version 0.11.0-1
dpkg-buildpackage: info: source distribution unstable
dpkg-buildpackage: info: source changed by Equivs Dummy Package Generator <root@devoid>
dpkg-buildpackage: info: host architecture amd64
 dpkg-source --before-build .
 debian/rules clean
dh clean
   dh_clean
 debian/rules binary
dh binary
   dh_update_autotools_config
   dh_autoreconf
   create-stamp debian/debhelper-build-stamp
   dh_prep
   dh_auto_install --destdir=debian/rust-trippy-build-deps/
   dh_install
   dh_installdocs
   dh_installchangelogs
   dh_perl
   dh_link
   dh_strip_nondeterminism
   dh_compress
   dh_fixperms
   dh_missing
   dh_installdeb
   dh_gencontrol
   dh_md5sums
   dh_builddeb
dpkg-deb: building package 'rust-trippy-build-deps' in '../rust-trippy-build-deps_0.11.0-1_all.deb'.
 dpkg-genbuildinfo --build=binary -O../rust-trippy-build-deps_0.11.0-1_amd64.buildinfo
 dpkg-genchanges --build=binary -O../rust-trippy-build-deps_0.11.0-1_amd64.changes
dpkg-genchanges: info: binary-only upload (no source code included)
 dpkg-source --after-build .
dpkg-buildpackage: info: binary-only upload (no source included)

The package has been created.
Attention, the package has been created in the current directory,
not in ".." as indicated by the message above!
root@devoid /w/t/trippy (debian/sid)# apt install ./rust-trippy-build-deps_0.11.0-1_all.deb
Note, selecting 'rust-trippy-build-deps' instead of './rust-trippy-build-deps_0.11.0-1_all.deb'
rust-trippy-build-deps is already the newest version (0.11.0-1).
Summary:
  Upgrading: 0, Installing: 0, Removing: 0, Not Upgrading: 10
----

This can't be checked like Andreas did, because the .deb is there, unless I
cross check dpkg -I with d/control - but what's the point? And the warning is
really hard to spot. Please just stop when there's an error.