meson: custom_target does not finish command properly

This comes from the wip meson port of libqmi and has also been commented in meson’s google groups.

I want to concatenate a series of generated files, along with an existing one, into a new file, which is then used to generate documentation by using gtkdoc. I’m just using cat to concatenate files in a custom_target. However, looks like cat stops halfway and this makes the documentation generation to fail because the resulting file doesn’t contain the whole data.

This procedure is done in the following way:

doc_module = 'libqmi-glib'
name = doc_module + '-sections.txt'

sections_txt = custom_target(
  name,
  input: ['libqmi-glib-common.sections'] + gen_sections,
  output: name,
  capture: true,
  command: [find_program('cat'), '@INPUT@'],
)

gen_sections is a set of generated files by using a previous custom_target and libqmi-glib-common.sections is an existing file which is also concatenated into a file called libqmi-glib-sections.txt.

gnome.gtkdoc(
  doc_module,
  main_xml: doc_module + '-docs.xml',
  src_dir: src_dirs,
  ignore_headers: private_headers,
  include_directories: top_inc,
  dependencies: libqmi_glib_dep,
  namespace: 'qmi',
  scan_args: scan_args,
  fixxref_args: fixxref_args,
  content_files: [sections_txt, version_xml],
  install: true,
)

The sections_txt target seems to stop at some point after/when gtkdoc is executed. The resulting file should be 306492 bytes but is only 240095 bytes. If I execute the libqmi-glib-sections.txt target alone, the resulting file size is correct, 306492 bytes and if gtkdoc documentation generation is executed after, then the process ends properly.

I have also tried using the console parameter instead of the capture parameter, because its documentation says the following:

console (added 0.48) keyword argument conflicts with capture, and **is meant for commands that are resource-intensive and take a long time to finish**. With the Ninja backend, setting this will add this target to Ninja's console pool, which has special properties such as not buffering stdout and serializing all targets in this pool.

This was just in case the command was killed due to the spent on the command, but it also doesn’t work.