Add MSYS2 platform package requirement

[otegami]

Issue

On MSYS2 environments, installing gems that depend on pkgconf might fail because the pkgconf system package cannot be automatically installed.

Cause

The pkg-config gem was missing MSYS2 platform
configuration in its system package requirements.
Without this, the rubygems-requirements-system gem cannot automatically install the pkgconfg system
package on MSYS2 environments.

Solution

Add system: pkgconf: msys2: pkgconf to the gemspec requirements.
This works with rubygems-requirements-system which supports MSYS2 platform.

[kou]

Could you add CI jobs?

gem install pkg-config never failed even if there is no pkgconf. If pkgconf doesn't exist, pkg-config just doesn't use search paths that are known by pkgconf.

[otegami]

This commit 3ab9fea raised the following error. I'm trying to fix it now on my fork.

Failure: test_cflags(PkgConfigTest)
D:/a/pkg-config/pkg-config/test/test-pkg-config.rb:202:in 'PkgConfigTest#assert_pkg_config'
D:/a/pkg-config/pkg-config/test/test-pkg-config.rb:37:in 'PkgConfigTest#test_cflags'
     34: 
     35:   def test_cflags
     36:     omit("Fragile on macOS") if RUBY_PLATFORM.include?("darwin")
  => 37:     assert_pkg_config("glib-2.0", ["--cflags"], @glib.cflags)
     38:   end
     39: 
     40:   def test_cflags_only_I
<"-ID:/a/_temp/msys64/clang64/include/glib-2.0 -I/tmp/local/lib/glib-2.0/include"> expected but was
<"-ID:/a/_temp/msys64/clang64/include/glib-2.0 -I/tmp/local/lib/glib-2.0/include -ID:/a/_temp/msys64/clang64/include">

diff:
? -ID:/a/_temp/msys64/clang64/include/glib-2.0 -I/tmp/local/lib/glib-2.0/include -ID:/a/_temp/msys64/clang64/include
Error: <"-ID:/a/_temp/msys64/clang64/include/glib-2.0 -I/tmp/local/lib/glib-2.0/include"> expected but was
<"-ID:/a/_temp/msys64/clang64/include/glib-2.0 -I/tmp/local/lib/glib-2.0/include -ID:/a/_temp/msys64/clang64/include">.

https://github.com/otegami/pkg-config/actions/runs/19723831055/job/56511296660#step:5:9

[otegami]

I investigated the test failure on MSYS2 and found that the pkg-config gem includes cflags from Requires.private dependencies, while pkgconf does not.
Should the pkg-config gem's behavior be changed to match pkgconf (i.e., exclude Requires.private cflags)?

Investigation details

The test_cflags and test_cflags_only_I tests fail on MSYS2 because the pkg-config gem outputs an extra include path compared to pkgconf.

ref: https://github.com/otegami/pkg-config/actions/runs/19724901555/job/56514480765#step:5:20

Debug output on MSYS2 (UCRT64)

=== glib-2.0.pc ===
prefix=/ucrt64
bindir=${prefix}/bin
datadir=${prefix}/share
includedir=${prefix}/include
libdir=${prefix}/lib
glib_genmarshal=${bindir}/glib-genmarshal.exe
gobject_query=${bindir}/gobject-query
glib_mkenums=${bindir}/glib-mkenums.exe
glib_valgrind_suppressions=${datadir}/glib-2.0/valgrind/glib.supp
Name: GLib
Description: C Utility Library
Version: 2.86.2
Requires.private: libpcre2-8 >= 10.32
Libs: -L${libdir} -lglib-2.0 -lintl
Libs.private: -lws2_32 -lole32 -lwinmm -lshlwapi -luuid -latomic -lm
Cflags: -I${includedir}/glib-2.0 -I${libdir}/glib-2.0/include

=== libpcre2-8.pc ===
(glib-2.0.pc has "Requires.private: libpcre2-8 >= 10.32")

# Package Information for pkg-config
prefix=/ucrt64
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include
Name: libpcre2-8
Description: PCRE2 - Perl compatible regular expressions C library (2nd API) with 8 bit character support
Version: 10.47
License: BSD-3-Clause WITH PCRE2-exception
Libs: -L${libdir} -lpcre2-8
Libs.private:
Cflags: -I${includedir}

=== pkgconf --cflags libpcre2-8 ===
(empty output - pkgconf filters out system include path)

=== pkgconf --cflags glib-2.0 ===
-ID:/a/_temp/msys64/ucrt64/include/glib-2.0 -ID:/a/_temp/msys64/ucrt64/lib/glib-2.0/include

=== pkg-config gem cflags ===
-ID:/a/_temp/msys64/ucrt64/include/glib-2.0 -ID:/a/_temp/msys64/ucrt64/lib/glib-2.0/include -ID:/a/_temp/msys64/ucrt64/include

Root cause

The pkg-config gem includes cflags from Requires.private dependencies, while pkgconf does not include them in --cflags output.

In the collect_cflags method, the gem uses all_required_packages which includes both Requires and Requires.private:

https://github.com/ruby-gnome/pkg-config/blob/ca9ad8a71aa5a6d77d0b2a2f6f8dcabc9cb63d6a/lib/pkg-config.rb#L530-L535

Current behavior comparison

	pkgconf	pkg-config gem
cflags	Excludes Requires.private	Includes Requires.private
libs	Excludes Requires.private	Excludes Requires.private

[kou]

Hmm. I think that Requires.private's Cflags is needed in some situations but I can't remember them...

OK. Let's use Requires.private only for static linking mode.

Could you work on it as a separated PR?

It may be something like the following:

diff --git a/lib/pkg-config.rb b/lib/pkg-config.rb
index 197af8b..6ef996c 100644
--- a/lib/pkg-config.rb
+++ b/lib/pkg-config.rb
@@ -37,56 +37,58 @@ module PKGConfig
     /mswin/.match(RUBY_PLATFORM) and /^cl\b/.match(RbConfig::CONFIG["CC"])
   end
 
-  def package_config(package)
+  def package_config(package, **options)
     PackageConfig.new(package,
-                      :msvc_syntax => msvc?,
-                      :override_variables => @@override_variables,
-                      :paths => @@paths)
+                      {
+                        msvc_syntax: msvc?,
+                        override_variables: @@override_variables,
+                        paths: @@paths,
+                      }.merge(options))
   end
 
-  def exist?(pkg)
-    package_config(pkg).exist?
+  def exist?(pkg, **options)
+    package_config(pkg, **options).exist?
   end
 
-  def libs(pkg)
-    package_config(pkg).libs
+  def libs(pkg, **options)
+    package_config(pkg, **options).libs
   end
 
-  def libs_only_l(pkg)
-    package_config(pkg).libs_only_l
+  def libs_only_l(pkg, **options)
+    package_config(pkg, **options).libs_only_l
   end
 
-  def libs_only_L(pkg)
-    package_config(pkg).libs_only_L
+  def libs_only_L(pkg, **options)
+    package_config(pkg, **options).libs_only_L
   end
 
-  def cflags(pkg)
-    package_config(pkg).cflags
+  def cflags(pkg, **options)
+    package_config(pkg, **options).cflags
   end
 
-  def cflags_only_I(pkg)
-    package_config(pkg).cflags_only_I
+  def cflags_only_I(pkg, **options)
+    package_config(pkg, **options).cflags_only_I
   end
 
-  def cflags_only_other(pkg)
-    package_config(pkg).cflags_only_other
+  def cflags_only_other(pkg, **options)
+    package_config(pkg, **options).cflags_only_other
   end
 
-  def modversion(pkg)
-    package_config(pkg).version
+  def modversion(pkg, **options)
+    package_config(pkg, **options).version
   end
 
-  def description(pkg)
-    package_config(pkg).description
+  def description(pkg, **options)
+    package_config(pkg, **options).description
   end
 
-  def variable(pkg, name)
-    package_config(pkg).variable(name)
+  def variable(pkg, name, **options)
+    package_config(pkg, **options).variable(name)
   end
 
-  def check_version?(pkg, major=0, minor=0, micro=0)
+  def check_version?(pkg, major=0, minor=0, micro=0, **options)
     return false unless exist?(pkg)
-    ver = modversion(pkg).split(".").collect {|item| item.to_i}
+    ver = modversion(pkg, **options).split(".").collect {|item| item.to_i}
     (0..2).each {|i| ver[i] = 0 unless ver[i]}
 
     (ver[0] > major ||
@@ -95,7 +97,7 @@ module PKGConfig
       ver[2] >= micro))
   end
 
-  def have_package(pkg, major=nil, minor=0, micro=0)
+  def have_package(pkg, major=nil, minor=0, micro=0, **options)
     message = "#{pkg}"
     unless major.nil?
       message << " version (>= #{major}.#{minor}.#{micro})"
@@ -105,7 +107,7 @@ module PKGConfig
       if check_version?(pkg, major, minor, micro)
         "yes (#{modversion(pkg)})"
       else
-        if exist?(pkg)
+        if exist?(pkg, **options)
           "no (#{modversion(pkg)})"
         else
           "no (nonexistent)"
@@ -408,6 +410,7 @@ class PackageConfig
     @paths.unshift(*(@options[:paths] || []))
     @paths = normalize_paths(@paths)
     @msvc_syntax = @options[:msvc_syntax]
+    @static = @options[:static]
     @variables = @declarations = nil
     override_variables = self.class.custom_override_variables
     @override_variables = parse_override_variables(override_variables)
@@ -528,7 +531,12 @@ class PackageConfig
 
   private
   def collect_cflags
-    target_packages = [self, *all_required_packages]
+    target_packages = [self]
+    if @static
+      target_packages += all_required_packages
+    else
+      target_packages += required_packages
+    end
     cflags_set = []
     target_packages.each do |package|
       cflags_set << package.declaration("Cflags")
@@ -580,7 +588,12 @@ class PackageConfig
   end
 
   def collect_libs
-    target_packages = [*required_packages, self]
+    if @static
+      target_packages = required_packages
+    else
+      target_packages = all_required_packages
+    end
+    target_packages += [self]
     libs_set = []
     target_packages.each do |package|
       libs_set << package.declaration("Libs")

[otegami]

@kou
Thank you so much. I've just created the PR for using Requires.private only for static linking mode.

• ref: Use Requires.private only for static linking #42