Merge pull request #6203 from xclaesse/override-dependency

Add meson.override_dependency()

docs/markdown/Reference-manual.md

@@ -445,6 +445,10 @@ arguments:
   [`dependency()`](#dependency), etc. Note that this means the
   fallback dependency may be a not-found dependency, in which
   case the value of the `required:` kwarg will be obeyed.
+  *Since 0.54.0* `'subproj_dep'` argument can be omitted in the case the
+  subproject used `meson.override_dependency('dependency_name', subproj_dep)`.
+  In that case, the `fallback` keyword argument can be a single string instead
+  of a list of 2 strings.
 - `language` *(added 0.42.0)* defines what language-specific
   dependency to find if it's available for multiple languages.
 - `method` defines the way the dependency is detected, the default is
@@ -1825,12 +1829,21 @@ the following methods.
 - `override_find_program(progname, program)` [*(Added
   0.46.0)*](Release-notes-for-0.46.0.md#can-override-find_program)
   specifies that whenever `find_program` is used to find a program
-  named `progname`, Meson should not not look it up on the system but
+  named `progname`, Meson should not look it up on the system but
   instead return `program`, which may either be the result of
   `find_program`, `configure_file` or `executable`.
 
   If `program` is an `executable`, it cannot be used during configure.
 
+- `override_dependency(name, dep_object)` [*(Added
+  0.54.0)*](Release-notes-for-0.54.0.md#override-dependency)
+  specifies that whenever `dependency(name, ...)` is used, Meson should not
+  look it up on the system but instead return `dep_object`, which may either be
+  the result of `dependency()` or `declare_dependency()`. It takes optional
+  `native` keyword arguments. Doing this in a subproject allows the parent
+  project to retrieve the dependency without having to know the dependency
+  variable name: `dependency(name, fallback : subproject_name)`.
+
 - `project_version()` returns the version string specified in
   `project` function call.
 

docs/markdown/snippets/override_dependency.md

@@ -0,0 +1,65 @@
+## `dependency()` consistency
+
+The first time a dependency is found, using `dependency('foo', ...)`, the return
+value is now cached. Any subsequent call will return the same value as long as
+version requested match, otherwise not-found dependency is returned. This means
+that if a system dependency is first found, it won't fallback to a subproject
+in a subsequent call any more and will rather return not-found instead if the
+system version does not match. Similarly, if the first call returns the subproject
+fallback dependency, it will also return the subproject dependency in a subsequent
+call even if no fallback is provided.
+
+For example, if the system has `foo` version 1.0:
+```meson
+# d2 is set to foo_dep and not the system dependency, even without fallback argument.
+d1 = dependency('foo', version : '>=2.0', required : false,
+                fallback : ['foo', 'foo_dep'])
+d2 = dependency('foo', version : '>=1.0', required : false)
+```
+```meson
+# d2 is not-found because the first call returned the system dependency, but its version is too old for 2nd call.
+d1 = dependency('foo', version : '>=1.0', required : false)
+d2 = dependency('foo', version : '>=2.0', required : false,
+                fallback : ['foo', 'foo_dep'])
+```
+
+## Override `dependency()`
+
+It is now possible to override the result of `dependency()` to point
+to any dependency object you want. The overriding is global and applies to
+every subproject from there on.
+
+For example, this subproject provides 2 libraries with version 2.0:
+
+```meson
+project(..., version : '2.0')
+
+libfoo = library('foo', ...)
+foo_dep = declare_dependency(link_with : libfoo)
+meson.override_dependency('foo', foo_dep)
+
+libbar = library('bar', ...)
+bar_dep = declare_dependency(link_with : libbar)
+meson.override_dependency('bar', bar_dep)
+```
+
+Assuming the system has `foo` and `bar` 1.0 installed, and master project does this:
+```meson
+foo_dep = dependency('foo', version : '>=2.0', fallback : ['foo', 'foo_dep'])
+bar_dep = dependency('bar')
+```
+
+This used to mix system 1.0 version and subproject 2.0 dependencies, but thanks
+to the override `bar_dep` is now set to the subproject's version instead.
+
+Another case this can be useful is to force a subproject to use a specific dependency.
+If the subproject does `dependency('foo')` but the main project wants to provide
+its own implementation of `foo`, it can for example call
+`meson.override_dependency('foo', declare_dependency(...))` before configuring the
+subproject.
+
+## Simplified `dependency()` fallback
+
+In the case a subproject `foo` calls `meson.override_dependency('foo-2.0', foo_dep)`,
+the parent project can omit the dependency variable name in fallback keyword
+argument: `dependency('foo-2.0', fallback : 'foo')`.

mesonbuild/build.py

@@ -106,6 +106,12 @@ def get_target_macos_dylib_install_name(ld) -> str:
 class InvalidArguments(MesonException):
     pass
 
+class DependencyOverride:
+    def __init__(self, dep, node, explicit=True):
+        self.dep = dep
+        self.node = node
+        self.explicit = explicit
+
 class Build:
     """A class that holds the status of one build including
     all dependencies and so on.
@@ -141,6 +147,7 @@ class Build:
         self.test_setup_default_name = None
         self.find_overrides = {}
         self.searched_programs = set() # The list of all programs that have been searched for.
+        self.dependency_overrides = PerMachine({}, {})
 
     def copy(self):
         other = Build(self.environment)

mesonbuild/interpreter.py

@@ -1857,6 +1857,7 @@ class MesonMain(InterpreterObject):
                              'add_postconf_script': self.add_postconf_script_method,
                              'add_dist_script': self.add_dist_script_method,
                              'install_dependency_manifest': self.install_dependency_manifest_method,
+                             'override_dependency': self.override_dependency_method,
                              'override_find_program': self.override_find_program_method,
                              'project_version': self.project_version_method,
                              'project_license': self.project_license_method,
@@ -2013,6 +2014,29 @@ class MesonMain(InterpreterObject):
             raise InterpreterException('Second argument must be an external program or executable.')
         self.interpreter.add_find_program_override(name, exe)
 
+    @FeatureNew('meson.override_dependency', '0.53.0')
+    @permittedKwargs({'native'})
+    def override_dependency_method(self, args, kwargs):
+        if len(args) != 2:
+            raise InterpreterException('Override needs two arguments')
+        name = args[0]
+        dep = args[1]
+        if not isinstance(name, str) or not name:
+            raise InterpreterException('First argument must be a string and cannot be empty')
+        if hasattr(dep, 'held_object'):
+            dep = dep.held_object
+        if not isinstance(dep, dependencies.Dependency):
+            raise InterpreterException('Second argument must be a dependency object')
+        identifier = dependencies.get_dep_identifier(name, kwargs)
+        for_machine = self.interpreter.machine_from_native_kwarg(kwargs)
+        override = self.build.dependency_overrides[for_machine].get(identifier)
+        if override:
+            m = 'Tried to override dependency {!r} which has already been resolved or overridden at {}'
+            location = mlog.get_error_location_string(override.node.filename, override.node.lineno)
+            raise InterpreterException(m.format(name, location))
+        self.build.dependency_overrides[for_machine][identifier] = \
+            build.DependencyOverride(dep, self.interpreter.current_node)
+
     @noPosargs
     @permittedKwargs({})
     def project_version_method(self, args, kwargs):
@@ -3218,20 +3242,37 @@ external dependencies (including libraries) must go to "dependencies".''')
         # Check if we want this as a build-time / build machine or runt-time /
         # host machine dep.
         for_machine = self.machine_from_native_kwarg(kwargs)
-
         identifier = dependencies.get_dep_identifier(name, kwargs)
-        cached_dep = self.coredata.deps[for_machine].get(identifier)
-        if cached_dep:
+        wanted_vers = mesonlib.stringlistify(kwargs.get('version', []))
+
+        override = self.build.dependency_overrides[for_machine].get(identifier)
+        if override:
+            info = [mlog.blue('(overridden)' if override.explicit else '(cached)')]
+            cached_dep = override.dep
+            # We don't implicitly override not-found dependencies, but user could
+            # have explicitly called meson.override_dependency() with a not-found
+            # dep.
             if not cached_dep.found():
                 mlog.log('Dependency', mlog.bold(name),
-                         'found:', mlog.red('NO'), mlog.blue('(cached)'))
+                         'found:', mlog.red('NO'), *info)
                 return identifier, cached_dep
-
-            # Verify the cached dep version match
-            wanted_vers = mesonlib.stringlistify(kwargs.get('version', []))
             found_vers = cached_dep.get_version()
-            if not wanted_vers or mesonlib.version_compare_many(found_vers, wanted_vers)[0]:
+            if not self.check_version(wanted_vers, found_vers):
+                mlog.log('Dependency', mlog.bold(name),
+                         'found:', mlog.red('NO'),
+                         'found', mlog.normal_cyan(found_vers), 'but need:',
+                         mlog.bold(', '.join(["'{}'".format(e) for e in wanted_vers])),
+                         *info)
+                return identifier, NotFoundDependency(self.environment)
+        else:
             info = [mlog.blue('(cached)')]
+            cached_dep = self.coredata.deps[for_machine].get(identifier)
+            if cached_dep:
+                found_vers = cached_dep.get_version()
+                if not self.check_version(wanted_vers, found_vers):
+                    return identifier, None
+
+        if cached_dep:
             if found_vers:
                 info = [mlog.normal_cyan(found_vers), *info]
             mlog.log('Dependency', mlog.bold(name),
@@ -3241,7 +3282,7 @@ external dependencies (including libraries) must go to "dependencies".''')
         return identifier, None
 
     @staticmethod
-    def check_subproject_version(wanted, found):
+    def check_version(wanted, found):
         if not wanted:
             return True
         if found == 'undefined' or not mesonlib.version_compare_many(found, wanted)[0]:
@@ -3251,11 +3292,35 @@ external dependencies (including libraries) must go to "dependencies".''')
     def notfound_dependency(self):
         return DependencyHolder(NotFoundDependency(self.environment), self.subproject)
 
-    def get_subproject_dep(self, display_name, dirname, varname, kwargs):
+    def verify_fallback_consistency(self, dirname, varname, cached_dep):
+        subi = self.subprojects.get(dirname)
+        if not cached_dep or not varname or not subi or not cached_dep.found():
+            return
+        dep = subi.get_variable_method([varname], {})
+        if dep.held_object != cached_dep:
+            m = 'Inconsistency: Subproject has overriden the dependency with another variable than {!r}'
+            raise DependencyException(m.format(varname))
+
+    def get_subproject_dep(self, name, display_name, dirname, varname, kwargs):
+        required = kwargs.get('required', True)
+        wanted = mesonlib.stringlistify(kwargs.get('version', []))
+        subproj_path = os.path.join(self.subproject_dir, dirname)
         dep = self.notfound_dependency()
         try:
             subproject = self.subprojects[dirname]
+            _, cached_dep = self._find_cached_dep(name, kwargs)
+            if varname is None:
+                # Assuming the subproject overriden the dependency we want
+                if cached_dep:
+                    if required and not cached_dep.found():
+                        m = 'Dependency {!r} is not satisfied'
+                        raise DependencyException(m.format(display_name))
+                    return DependencyHolder(cached_dep, self.subproject)
+                else:
+                    m = 'Subproject {} did not override dependency {}'
+                    raise DependencyException(m.format(subproj_path, display_name))
             if subproject.found():
+                self.verify_fallback_consistency(dirname, varname, cached_dep)
                 dep = self.subprojects[dirname].get_variable_method([varname], {})
         except InvalidArguments:
             pass
@@ -3264,10 +3329,6 @@ external dependencies (including libraries) must go to "dependencies".''')
             raise InvalidCode('Fetched variable {!r} in the subproject {!r} is '
                               'not a dependency object.'.format(varname, dirname))
 
-        required = kwargs.get('required', True)
-        wanted = mesonlib.stringlistify(kwargs.get('version', []))
-        subproj_path = os.path.join(self.subproject_dir, dirname)
-
         if not dep.found():
             if required:
                 raise DependencyException('Could not find dependency {} in subproject {}'
@@ -3278,7 +3339,7 @@ external dependencies (including libraries) must go to "dependencies".''')
             return dep
 
         found = dep.held_object.get_version()
-        if not self.check_subproject_version(wanted, found):
+        if not self.check_version(wanted, found):
             if required:
                 raise DependencyException('Version {} of subproject dependency {} already '
                                           'cached, requested incompatible version {} for '
@@ -3330,6 +3391,15 @@ external dependencies (including libraries) must go to "dependencies".''')
             raise
         if not d.found() and not_found_message:
             self.message_impl([not_found_message])
+            self.message_impl([not_found_message])
+        # Override this dependency to have consistent results in subsequent
+        # dependency lookups.
+        if name and d.found():
+            for_machine = self.machine_from_native_kwarg(kwargs)
+            identifier = dependencies.get_dep_identifier(name, kwargs)
+            if identifier not in self.build.dependency_overrides[for_machine]:
+                self.build.dependency_overrides[for_machine][identifier] = \
+                    build.DependencyOverride(d.held_object, node, explicit=False)
         return d
 
     def dependency_impl(self, name, display_name, kwargs):
@@ -3353,6 +3423,9 @@ external dependencies (including libraries) must go to "dependencies".''')
 
         identifier, cached_dep = self._find_cached_dep(name, kwargs)
         if cached_dep:
+            if has_fallback:
+                dirname, varname = self.get_subproject_infos(kwargs)
+                self.verify_fallback_consistency(dirname, varname, cached_dep)
             if required and not cached_dep.found():
                 m = 'Dependency {!r} was already checked and was not found'
                 raise DependencyException(m.format(display_name))
@@ -3363,7 +3436,7 @@ external dependencies (including libraries) must go to "dependencies".''')
         if has_fallback:
             dirname, varname = self.get_subproject_infos(kwargs)
             if dirname in self.subprojects:
-                return self.get_subproject_dep(name, dirname, varname, kwargs)
+                return self.get_subproject_dep(name, display_name, dirname, varname, kwargs)
 
         wrap_mode = self.coredata.get_builtin_option('wrap_mode')
         forcefallback = wrap_mode == WrapMode.forcefallback and has_fallback
@@ -3371,7 +3444,6 @@ external dependencies (including libraries) must go to "dependencies".''')
             self._handle_featurenew_dependencies(name)
             kwargs['required'] = required and not has_fallback
             dep = dependencies.find_external_dependency(name, self.environment, kwargs)
-
             kwargs['required'] = required
             # Only store found-deps in the cache
             # Never add fallback deps to self.coredata.deps since we
@@ -3383,7 +3455,7 @@ external dependencies (including libraries) must go to "dependencies".''')
                 return DependencyHolder(dep, self.subproject)
 
         if has_fallback:
-            return self.dependency_fallback(display_name, kwargs)
+            return self.dependency_fallback(name, display_name, kwargs)
 
         return self.notfound_dependency()
 
@@ -3411,13 +3483,15 @@ external dependencies (including libraries) must go to "dependencies".''')
         mlog.warning(*message, location=self.current_node)
 
     def get_subproject_infos(self, kwargs):
-        fbinfo = kwargs['fallback']
-        check_stringlist(fbinfo)
-        if len(fbinfo) != 2:
-            raise InterpreterException('Fallback info must have exactly two items.')
+        fbinfo = mesonlib.stringlistify(kwargs['fallback'])
+        if len(fbinfo) == 1:
+            FeatureNew('Fallback without variable name', '0.53.0').use(self.subproject)
+            return fbinfo[0], None
+        elif len(fbinfo) != 2:
+            raise InterpreterException('Fallback info must have one or two items.')
         return fbinfo
 
-    def dependency_fallback(self, display_name, kwargs):
+    def dependency_fallback(self, name, display_name, kwargs):
         required = kwargs.get('required', True)
         if self.coredata.get_builtin_option('wrap_mode') == WrapMode.nofallback:
             mlog.log('Not looking for a fallback subproject for the dependency',
@@ -3439,7 +3513,7 @@ external dependencies (including libraries) must go to "dependencies".''')
             'required': required,
         }
         self.do_subproject(dirname, 'meson', sp_kwargs)
-        return self.get_subproject_dep(display_name, dirname, varname, kwargs)
+        return self.get_subproject_dep(name, display_name, dirname, varname, kwargs)
 
     @FeatureNewKwargs('executable', '0.42.0', ['implib'])
     @permittedKwargs(permitted_kwargs['executable'])

run_unittests.py

@@ -3980,11 +3980,17 @@ recommended as it is not supported on some platforms''')
                 {
                     'descriptive_name': 'sub',
                     'name': 'sub',
-                    'version': 'undefined'
-                }
+                    'version': '1.0'
+                },
+                {
+                    'descriptive_name': 'sub-novar',
+                    'name': 'sub_novar',
+                    'version': '1.0',
+                },
             ]
         }
-        self.assertDictEqual(res, expected)
+        res['subprojects'] = sorted(res['subprojects'], key=lambda i: i['name'])
+        self.assertDictEqual(expected, res)
 
     def test_introspection_target_subproject(self):
         testdir = os.path.join(self.common_test_dir, '45 subproject')
@@ -4555,7 +4561,7 @@ class FailureTests(BasePlatformTests):
             raise unittest.SkipTest('zlib not found with pkg-config')
         a = (("dependency('zlib', method : 'fail')", "'fail' is invalid"),
              ("dependency('zlib', static : '1')", "[Ss]tatic.*boolean"),
-             ("dependency('zlib', version : 1)", "[Vv]ersion.*string or list"),
+             ("dependency('zlib', version : 1)", "Item must be a list or one of <class 'str'>"),
              ("dependency('zlib', required : 1)", "[Rr]equired.*boolean"),
              ("dependency('zlib', method : 1)", "[Mm]ethod.*string"),
              ("dependency('zlibfail')", self.dnf),)
@@ -4772,6 +4778,17 @@ class FailureTests(BasePlatformTests):
         self.assertMesonOutputs("warning('Array:', ['a', 'b'])",
                                 r"WARNING:.* Array: \['a', 'b'\]")
 
+    def test_override_dependency_twice(self):
+        self.assertMesonRaises("meson.override_dependency('foo', declare_dependency())\n" +
+                               "meson.override_dependency('foo', declare_dependency())",
+                               """Tried to override dependency 'foo' which has already been resolved or overridden""")
+
+    @unittest.skipIf(is_windows(), 'zlib is not available on Windows')
+    def test_override_resolved_dependency(self):
+        self.assertMesonRaises("dependency('zlib')\n" +
+                               "meson.override_dependency('zlib', declare_dependency())",
+                               """Tried to override dependency 'zlib' which has already been resolved or overridden""")
+
 @unittest.skipUnless(is_windows() or is_cygwin(), "requires Windows (or Windows via Cygwin)")
 class WindowsTests(BasePlatformTests):
     '''

test cases/common/102 subproject subdir/meson.build

@@ -4,3 +4,24 @@ libSub = dependency('sub', fallback: ['sub', 'libSub'])
 
 exe = executable('prog', 'prog.c', dependencies: libSub)
 test('subproject subdir', exe)
+
+# Verify the subproject has placed dependency override.
+dependency('sub-1.0')
+
+# Verify we can now take 'sub' dependency without fallback, but only version 1.0.
+dependency('sub')
+d = dependency('sub', version : '>=2.0', required : false)
+assert(not d.found(), 'version should not match')
+
+# Verify that not-found does not get cached, we can still fallback afterward.
+dependency('sub2', required : false)
+d = dependency('sub2', fallback: ['sub', 'libSub'])
+assert(d.found(), 'Should fallback even if a previous call returned not-found')
+
+# Verify we can get a fallback dependency without specifying the variable name,
+# because the subproject overridden 'sub-novar'.
+dependency('sub-novar', fallback : 'sub_novar')
+
+# Verify a subproject can force a dependency to be not-found
+d = dependency('sub-notfound', fallback : 'sub_novar', required : false)
+assert(not d.found(), 'Dependency should be not-found')

test cases/common/102 subproject subdir/subprojects/sub/lib/meson.build

@@ -1,2 +1,3 @@
 lib = static_library('sub', 'sub.c')
 libSub = declare_dependency(include_directories: include_directories('.'), link_with: lib)
+meson.override_dependency('sub-1.0', libSub)

test cases/common/102 subproject subdir/subprojects/sub/meson.build

@@ -1,2 +1,2 @@
-project('sub', 'c')
+project('sub', 'c', version : '1.0')
 subdir('lib')

test cases/common/102 subproject subdir/subprojects/sub_novar/meson.build

@@ -0,0 +1,4 @@
+project('sub-novar', 'c', version : '1.0')
+
+meson.override_dependency('sub-novar', declare_dependency())
+meson.override_dependency('sub-notfound', dependency('', required : false))

test cases/failing/100 fallback consistency/meson.build

@@ -0,0 +1,7 @@
+project('proj', 'c')
+
+# The first call succeed and cache the value of 'sub' dependency. The 2nd call
+# should return the cached value, but still verify the fallback variable is
+# consistent.
+dependency('sub', fallback : ['sub', 'dep1'])
+dependency('sub', fallback : ['sub', 'dep2'])

test cases/failing/100 fallback consistency/subprojects/sub/meson.build

@@ -0,0 +1,5 @@
+project('proj', 'c')
+
+dep1 = declare_dependency()
+dep2 = declare_dependency()
+meson.override_dependency('sub', dep1)

test cases/failing/99 fallback consistency/meson.build

@@ -0,0 +1,4 @@
+project('proj', 'c')
+
+# Subproject overrides 'sub' with another variable than dep2. This should fail.
+dependency('sub', fallback : ['sub', 'dep2'])

test cases/failing/99 fallback consistency/subprojects/sub/meson.build

@@ -0,0 +1,5 @@
+project('proj', 'c')
+
+dep1 = declare_dependency()
+dep2 = declare_dependency()
+meson.override_dependency('sub', dep1)

test cases/linuxlike/5 dependency versions/meson.build

@@ -38,32 +38,32 @@ somelibver = dependency('somelib',
   fallback : ['somelibnover', 'some_dep'])
 assert(somelibver.type_name() == 'internal', 'somelibver should be of type "internal", not ' + somelibver.type_name())
 # Find an internal dependency again with the same name and a specific version
-somelib = dependency('somelib',
+somelib = dependency('somelib2',
   version : '== 0.1',
   fallback : ['somelib', 'some_dep'])
 # Find an internal dependency again even if required = false
-somelib_reqfalse = dependency('somelib',
+somelib_reqfalse = dependency('somelib3',
   required: false,
   fallback : ['somelib', 'some_dep'])
 assert(somelib_reqfalse.found(), 'somelib should have been found')
 # Find an internal dependency again with the same name and incompatible version
-somelibver = dependency('somelib',
+somelibver = dependency('somelib4',
   version : '>= 0.3',
   fallback : ['somelibver', 'some_dep'])
 # Find an internal dependency again with impossible multi-version
-somelibver = dependency('somelib',
+somelibver = dependency('somelib5',
   version : ['>= 0.3', '<0.3'],
   required : false,
   fallback : ['somelibver', 'some_dep'])
 assert(not somelibver.found(), 'Dependency should not be found')
 # Find somelib again, but with a fallback that will fail because subproject does not exist
-somelibfail = dependency('somelib',
+somelibfail = dependency('somelib6',
   version : '>= 0.2',
   required : false,
   fallback : ['somelibfail', 'some_dep'])
 assert(somelibfail.found() == false, 'somelibfail found via wrong fallback')
 # Find somelib again, but with a fallback that will fail because dependency does not exist
-somefail_dep = dependency('somelib',
+somefail_dep = dependency('somelib7',
   version : '>= 0.2',
   required : false,
   fallback : ['somelib', 'somefail_dep'])
@@ -71,14 +71,21 @@ assert(somefail_dep.found() == false, 'somefail_dep found via wrong fallback')
 
 # Fallback should only be used if the primary was not found
 fallbackzlib_dep = dependency('zlib',
-  fallback : ['somelib', 'fakezlib_dep'])
+  fallback : ['fakezlib', 'fakezlib_dep'])
 assert(fallbackzlib_dep.type_name() == 'pkgconfig', 'fallbackzlib_dep should be of type "pkgconfig", not ' + fallbackzlib_dep.type_name())
 # Check that the above dependency was pkgconfig because the fallback wasn't
 # checked, not because the fallback didn't work
 fakezlib_dep = dependency('fakezlib',
-  fallback : ['somelib', 'fakezlib_dep'])
+  fallback : ['fakezlib', 'fakezlib_dep'])
 assert(fakezlib_dep.type_name() == 'internal', 'fakezlib_dep should be of type "internal", not ' + fakezlib_dep.type_name())
 
+# Verify that once we got a system dependency, we won't fallback if a newer
+# version is requested.
+d = dependency('zlib', version: '>= 999',
+  fallback : ['donotexist', 'fakezlib_dep'],
+  required: false)
+assert(not d.found(), 'version should not match and it should not fallback')
+
 # Check that you can find a dependency by not specifying a version after not
 # finding it by specifying a version. We add `static: true` here so that the
 # previously cached zlib dependencies don't get checked.

test cases/linuxlike/5 dependency versions/subprojects/fakezlib/meson.build

@@ -0,0 +1,3 @@
+project('some', 'c', version : '0.1')
+
+fakezlib_dep = declare_dependency()