meson: Improve certifi documentation on macOS

First, just installing certifi doesn't install the ca-cert in the
right location. The `Install Certificates.command` script also
symlinks the openssl cert.pem to the certifi ca cert file

Second, we can make it more likely that users will notice this if we
make it a warning. If we ever get a bug report about this despite
these measures, we can try to make this an error.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2707>

diff --git a/README.md b/README.md
index c727de1..9d5d79b 100644 (file)
--- a/README.md
+++ b/README.md
@@ -54,14 +54,14 @@ binary in your PATH.
 You can find [instructions for Windows below](#windows-prerequisites-setup).
 
 
-On macOS, you might need to execute "Install Certificates.command" from
-the Python folder in the user Applications folder or install it manually:
+On macOS, you might need to execute "Install Certificates.command" from the
+Python folder in the user Applications folder:
 
 ```
-  $ pip3 install certifi
+$ /Applications/Python\ 3.*/Install\ Certificates.command
 ```
 
-It will solve this issue:
+Otherwise you will get this error when downloading meson wraps:
 
 ```
 urllib.error.URLError: urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed

diff --git a/meson.build b/meson.build
index 619341a..3967832 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -48,6 +48,20 @@ if build_system == 'windows' and meson.version().version_compare('<0.60.0')
   endif
 endif
 
+# On macOS, you have to run "Install Certificates.command" otherwise Python
+# doesn't have access to the latest SSL CA Certificates, and Meson will fail to
+# download wrap files from websites that use, for example, Let's Encrypt.
+# We already recommend this in the README, but add a warning here as well.
+# Can't make this an error because the user might be using XCode's Python
+# 3 which doesn't have this script.
+if build_system == 'darwin'
+  python3_cacert_file = python3.get_path('data') / 'etc/openssl/cert.pem'
+  install_cert_cmd = '/Applications/Python @0@/Install Certificates.command'.format(python3.language_version())
+  if not fs.is_symlink(python3_cacert_file) and fs.is_file(install_cert_cmd)
+    warning('Please run "@0@" so that Python has access to the latest SSL certificates. Meson might fail to download some wraps without it.'.format(install_cert_cmd))
+  endif
+endif
+
 documented_projects = ''
 # Make it possible to use msys2 built zlib which fails
 # when not using the mingw toolchain as it uses unistd.h