find_library: Add 'has_headers' kwarg

A library without its headers is often useless, so it is common to check
them together.

docs/markdown/Reference-manual.md

@@ -1704,7 +1704,10 @@ the following methods:
   option can also be passed to the `required` keyword argument.
   *Since 0.49.0* if the keyword argument `disabler` is `true` and the
   dependency couldn't be found, return a [disabler object](#disabler-object)
-  instead of a not-found dependency.
+  instead of a not-found dependency. *Since 0.50.0* the `has_headers` keyword
+  argument can be a list of header files that must be found as well, using
+  `has_header()` method. All keyword arguments prefixed with `header_` will be
+  passed down to `has_header()` method with the prefix removed.
 
 - `first_supported_argument(list_of_strings)`, given a list of
   strings, returns the first argument that passes the `has_argument`

docs/markdown/snippets/find_library_header.md

@@ -0,0 +1,21 @@
+## Find library with its headers
+
+The `find_library()` method can now also verify if the library's headers are
+found in a single call, using the `has_header()` method internally.
+
+```meson
+# Aborts if the 'z' library is found but not its header file
+zlib = find_library('z', has_headers : 'zlib.h')
+# Returns not-found if the 'z' library is found but not its header file
+zlib = find_library('z', has_headers : 'zlib.h', required : false)
+```
+
+Any keyword argument with the `header_` prefix passed to `find_library()` will
+be passed to the `has_header()` method with the prefix removed.
+
+```meson
+libfoo = find_library('foo',
+  has_headers : ['foo.h', 'bar.h'],
+  header_prefix : '#include <baz.h>',
+  header_include_directories : include_directories('.'))
+```

mesonbuild/interpreter.py

@@ -900,6 +900,23 @@ class SubprojectHolder(InterpreterObject, ObjectHolder):
             raise InvalidArguments('Requested variable "{0}" not found.'.format(varname))
         return self.held_object.variables[varname]
 
+header_permitted_kwargs = set([
+    'required',
+    'prefix',
+    'no_builtin_args',
+    'include_directories',
+    'args',
+    'dependencies',
+])
+
+find_library_permitted_kwargs = set([
+    'has_headers',
+    'required',
+    'dirs',
+])
+
+find_library_permitted_kwargs |= set(['header_' + k for k in header_permitted_kwargs])
+
 class CompilerHolder(InterpreterObject):
     def __init__(self, compiler, env, subproject):
         InterpreterObject.__init__(self)
@@ -1345,14 +1362,7 @@ class CompilerHolder(InterpreterObject):
 
     @FeatureNew('compiler.check_header', '0.47.0')
     @FeatureNewKwargs('compiler.check_header', '0.50.0', ['required'])
-    @permittedKwargs({
-        'required',
-        'prefix',
-        'no_builtin_args',
-        'include_directories',
-        'args',
-        'dependencies',
-    })
+    @permittedKwargs(header_permitted_kwargs)
     def check_header_method(self, args, kwargs):
         if len(args) != 1:
             raise InterpreterException('check_header method takes exactly one argument.')
@@ -1380,14 +1390,7 @@ class CompilerHolder(InterpreterObject):
         return haz
 
     @FeatureNewKwargs('compiler.has_header', '0.50.0', ['required'])
-    @permittedKwargs({
-        'required',
-        'prefix',
-        'no_builtin_args',
-        'include_directories',
-        'args',
-        'dependencies',
-    })
+    @permittedKwargs(header_permitted_kwargs)
     def has_header_method(self, args, kwargs):
         if len(args) != 1:
             raise InterpreterException('has_header method takes exactly one argument.')
@@ -1414,14 +1417,7 @@ class CompilerHolder(InterpreterObject):
         return haz
 
     @FeatureNewKwargs('compiler.has_header_symbol', '0.50.0', ['required'])
-    @permittedKwargs({
-        'required',
-        'prefix',
-        'no_builtin_args',
-        'include_directories',
-        'args',
-        'dependencies',
-    })
+    @permittedKwargs(header_permitted_kwargs)
     def has_header_symbol_method(self, args, kwargs):
         if len(args) != 2:
             raise InterpreterException('has_header_symbol method takes exactly two arguments.')
@@ -1449,12 +1445,17 @@ class CompilerHolder(InterpreterObject):
         mlog.log('Header <{0}> has symbol'.format(hname), mlog.bold(symbol, True), msg, h)
         return haz
 
+    def notfound_library(self, libname):
+        lib = dependencies.ExternalLibrary(libname, None,
+                                           self.environment,
+                                           self.compiler.language,
+                                           silent=True)
+        return ExternalLibraryHolder(lib, self.subproject)
+
+    @FeatureNewKwargs('compiler.find_library', '0.50.0', ['has_headers'])
     @FeatureNewKwargs('compiler.find_library', '0.49.0', ['disabler'])
     @disablerIfNotFound
-    @permittedKwargs({
-        'required',
-        'dirs',
-    })
+    @permittedKwargs(find_library_permitted_kwargs)
     def find_library_method(self, args, kwargs):
         # TODO add dependencies support?
         if len(args) != 1:
@@ -1466,11 +1467,14 @@ class CompilerHolder(InterpreterObject):
         disabled, required, feature = extract_required_kwarg(kwargs, self.subproject)
         if disabled:
             mlog.log('Library', mlog.bold(libname), 'skipped: feature', mlog.bold(feature), 'disabled')
-            lib = dependencies.ExternalLibrary(libname, None,
-                                               self.environment,
-                                               self.compiler.language,
-                                               silent=True)
-            return ExternalLibraryHolder(lib, self.subproject)
+            return self.notfound_library(libname)
+
+        has_header_kwargs = {k[7:]: v for k, v in kwargs.items() if k.startswith('header_')}
+        has_header_kwargs['required'] = required
+        headers = mesonlib.stringlistify(kwargs.get('has_headers', []))
+        for h in headers:
+            if not self.has_header_method([h], has_header_kwargs):
+                return self.notfound_library(libname)
 
         search_dirs = mesonlib.stringlistify(kwargs.get('dirs', []))
         for i in search_dirs:

test cases/common/209 find_library and headers/foo.h

@@ -0,0 +1 @@
+#define VAL 42

test cases/common/209 find_library and headers/meson.build

@@ -0,0 +1,23 @@
+project('find library and headers', 'c')
+
+cc = meson.get_compiler('c')
+
+if not cc.find_library('z', required : false).found()
+  error('MESON_SKIP_TEST: zlib not found.')
+endif
+
+lib = cc.find_library('z',
+  has_headers : 'foo.h',
+  required : false)
+assert(not lib.found(), 'Header should be missing')
+
+lib = cc.find_library('z',
+  has_headers : 'foo.h',
+  header_include_directories : include_directories('.'))
+assert(lib.found(), 'Header should be found')
+
+lib = cc.find_library('z',
+  has_headers : ['foo.h', 'bar.h'],
+  header_include_directories : include_directories('.'),
+  required : false)
+assert(not lib.found(), 'One header should be missing')