CMake build fails if samples enabled but webready disabled, due to conntest sample dependency about exiv2

[ferdnyc]

Meson doesn't have the same issue, because the fake curl_dep is configured as a disabler when get_option('webready') is false. So, setting it as a dependency of conntest automatically removes it from the list of executables to be compiled.

exiv2/meson.build

Lines 70 to 74 in 41959b4

	if get_option('webready')
	curl_dep = dependency('libcurl', disabler: true, required: get_option('curl'))
	else
	curl_dep = dependency('', disabler: true, required: false)
	endif

exiv2/meson.build

Lines 158 to 165 in 41959b4

	samples = {
	'addmoddel': [],
	'conntest': curl_dep,
	'convert-test': [],
	'easyaccess-test': [],
	'exifcomment': [],
	'exifdata-test': [],
	'exifdata': [],

exiv2/meson.build

Lines 192 to 194 in 41959b4

	foreach s, d : samples
	executable(s, 'samples/@[email protected]'.format(s), dependencies: [exiv2_dep, d], include_directories: exiv2inc)
	endforeach

[kmilos]

Thank you for the report and the suggested fix. Are you able to submit a PR directly perhaps?

[ferdnyc]

...Actually, that Meson code seems strange to me — curl_dep is also set as a disabler when get_option('webready') is true, but it's also set required. (The first branch of the conditional is a bit odd there, as we already know get_option('webready') is true if we're on that branch.)

But dependency(..., disabler: true, required: true) seems like a nonsensical combination of options. In fact I'll be a bit surprised if Meson doesn't grumble about it, if the build is configured that way.

The net effect of all that is that curl is required when building a webready exiv2, which isn't the case in the CMake configuration. There, it's permissible to build with -DEXIV2_ENABLE_WEBREADY=1 -DEXIV2_ENABLE_CURL=0, and conntest does build and work (supporting http:// URLs only) even without curl.

[ferdnyc]

Thank you for the report and the suggested fix. Are you able to submit a PR directly perhaps?

Sure, will do.

[kmilos]

Actually, that Meson code seems strange to me

@neheb can best comment on Meson...

[ferdnyc]

(The first branch of the conditional is a bit odd there, as we already know get_option('webready') is true if we're on that branch.)

But dependency(..., disabler: true, required: true) seems like a nonsensical combination of options. In fact I'll be a bit surprised if Meson doesn't grumble about it, if the build is configured that way.

Nope, I read that wrong. I had it in my head that the code was,

if get_option('webready')
  curl_dep = dependency(
    'libcurl', disabler: true, required: get_option('webready'))

But it's not, it's

  curl_dep = dependency(
    'libcurl', disabler: true, required: get_option('curl'))

My mistake, sorry.

But the curl-is-effectively-required thing is still somewhat the case. (It will only affect conntest, though, since curl_dep isn't set as a library dependency unless curl_dep.found() is true. That way it will never disable the library build.)

But a disabler curl_dep will prevent the build of conntest when libcurl isn't available. In CMake, conntest — like libexiv2 itself — can be built "webready" with limited, HTTP-only support, even if it's not linked to curl.