Allow explicit disabling of optional dependencies in meson builds.

On some platforms, e.g. FreeBSD, there is a requirement to allow the user to disable support for features even when the required library is present.

Introduce tri-state options for the optional features: auto mimics the current behavior and is the default, enable requires libraries for the feature to be present, and disable disables the feature without checking the libraries.

doc/xml/release/2024/2.52.xml

@@ -1,6 +1,17 @@
 <release date="XXXX-XX-XX" version="2.52dev" title="UNDER DEVELOPMENT">
     <release-core-list>
         <release-improvement-list>
+            <release-item>
+                <github-pull-request id="2321"/>
+
+                <release-item-contributor-list>
+                    <release-item-contributor id="michael.schout"/>
+                    <release-item-reviewer id="david.steele"/>
+                </release-item-contributor-list>
+
+                <p>Allow explicit disabling of optional dependencies in meson builds.</p>
+            </release-item>
+
             <release-item>
                 <github-pull-request id="2312"/>
 

meson.build

@@ -144,7 +144,7 @@ endif
 lib_bz2 = cc.find_library('bz2')
 
 # Find optional lz4 library
-lib_lz4 = dependency('liblz4', required: false)
+lib_lz4 = dependency('liblz4', required: get_option('liblz4'))
 
 if lib_lz4.found()
     configuration.set('HAVE_LIBLZ4', true, description: 'Is liblz4 present?')
@@ -168,14 +168,14 @@ lib_z = dependency('zlib')
 configuration.set('ZLIB_CONST', true, description: 'Require zlib const input buffer')
 
 # Find optional libssh2 library
-lib_ssh2 = dependency('libssh2', required: false)
+lib_ssh2 = dependency('libssh2', required: get_option('libssh2'))
 
 if lib_ssh2.found()
     configuration.set('HAVE_LIBSSH2', true, description: 'Is libssh2 present?')
 endif
 
 # Find optional zstd library
-lib_zstd = dependency('libzstd', version: '>=1.0', required: false)
+lib_zstd = dependency('libzstd', version: '>=1.0', required: get_option('libzstd'))
 
 if lib_zstd.found()
     configuration.set('HAVE_LIBZST', true, description: 'Is libzstd present?')

meson_options.txt

@@ -1,2 +1,5 @@
 option('configdir', type: 'string', value: '/etc/pgbackrest', description: 'Configuration directory')
 option('fatal-errors', type: 'boolean', value: false, description: 'Stop compilation on first error')
+option('liblz4', type: 'feature', value: 'auto', description: 'Enable LZ4 compression support')
+option('libssh2', type: 'feature', value: 'auto', description: 'Enable SFTP storage support')
+option('libzstd', type: 'feature', value: 'auto', description: 'Enable Zstandard compression support')