Tighten warning for 'Requires.private' in simple pkg-config parser (#…

…26008)

Tightens up the logic for when we should warn about 'Requires.private'
(and also 'Requires'). We only need to warn when the compiler/linker
flags are not already handled by 'Cflags'/`Libs`.

Details:

`Requires`/`Requires.private` list what other pkg-config libraries are
needed, so that `pkg-config` can pull in the need dependencies/flags.
This ends up being a recursive operation (i.e. 'A' has 'Requires: B', so
we must process 'B.pc'). But if we already have the information needed,
this is unnecessary. So if we have 'Requires: B', but 'B' is already
listed in 'Libs', then for our purposes we have satisfied the
'Requires.'

Our simple pkg-config parser is used only for bundled third-party libs,
and we do not need to ability to recursively search other .pc files to
satisfy the requirements. So this PR uses the above logic to avoid
warning about `Requires`/`Requires.private` not being handled

This should resolve #26002

[Reviewed by @mppf  and @jhh67]

util/chplenv/third_party_utils.py

@@ -128,6 +128,20 @@ def pkgconfig_get_system_compile_args(pkg):
     cflags = cflags_line.split()
     return ([ ], cflags)
 
+# helper function to determine if we need to warn about 'Requires'/'Requires.private'
+# these fields list other packages that are required to link with this package
+# however, this only matters if the required package is not listed in
+# 'Libs'/'Libs.private' already
+# see https://people.freedesktop.org/~dbn/pkg-config-guide.html
+def _pkgconfig_should_warn_for_requires(d, private=False):
+    libs = d['Libs' if not private else 'Libs.private'].split()
+    requires = d['Requires' if not private else 'Requires.private'].split()
+    for req in requires:
+        lib_name = '-l' + req
+        if lib_name not in libs:
+            return True
+    return False
+
 #
 # Return compiler arguments required to use a bundled library
 # based on a pkg-config .pc file.
@@ -154,8 +168,16 @@ def pkgconfig_get_bundled_compile_args(pkg, ucp='', pcfile=''):
         return ([ ], [ ])
 
     if 'Requires' in d and d['Requires']:
-        warning("Simple pkg-config parser does not handle Requires")
-        warning("in {0}".format(pcpath))
+        warn = False
+        if 'Libs' in d:
+            warn = _pkgconfig_should_warn_for_requires(d)
+        else:
+            # no Libs, so no way to check if the required package is already included
+            warn = True
+
+        if warn:
+            warning("Simple pkg-config parser does not handle Requires")
+            warning("in {0}".format(pcpath))
 
     cflags = [ ]
 
@@ -236,11 +258,15 @@ def pkgconfig_get_bundled_link_args(pkg, ucp='', pcfile='',
     if d == None:
         return ([ ], [ ])
 
-    if 'Requires' in d and d['Requires']:
+    if d.get('Requires') and _pkgconfig_should_warn_for_requires(d):
         warning("Simple pkg-config parser does not handle Requires")
         warning("in {0}".format(pcpath))
 
-    if static and 'Requires.private' in d and d['Requires.private']:
+    if (
+        static
+        and d.get("Requires.private")
+        and _pkgconfig_should_warn_for_requires(d, private=True)
+    ):
         warning("Simple pkg-config parser does not handle Requires.private")
         warning("in {0}".format(pcpath))