dependency: Verify fallback variable consistency

This change made `5 dependency versions` unit test fail because now once
a subproject has been configured, the fallback variable is checked to be
consistent. So it has to use new subproject because 'somesub' was
already configured by previous tests.

7 files changed, 41 insertions, 5 deletions

diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index c247e63..77d64c4 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -3292,6 +3292,15 @@ external dependencies (including libraries) must go to "dependencies".''')
     def notfound_dependency(self):
         return DependencyHolder(NotFoundDependency(self.environment), self.subproject)
 
+    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', []))
@@ -3299,9 +3308,9 @@ external dependencies (including libraries) must go to "dependencies".''')
         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
-                _, cached_dep = self._find_cached_dep(name, kwargs)
                 if cached_dep:
                     if required and not cached_dep.found():
                         m = 'Dependency {!r} is not satisfied'
@@ -3311,6 +3320,7 @@ external dependencies (including libraries) must go to "dependencies".''')
                     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
@@ -3413,6 +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))
@@ -3431,7 +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
diff --git a/test cases/failing/100 fallback consistency/meson.build b/test cases/failing/100 fallback consistency/meson.build
new file mode 100644
index 0000000..ad2b226
--- /dev/null
+++ b/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'])
diff --git a/test cases/failing/100 fallback consistency/subprojects/sub/meson.build b/test cases/failing/100 fallback consistency/subprojects/sub/meson.build
new file mode 100644
index 0000000..12a6570
--- /dev/null
+++ b/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)
diff --git a/test cases/failing/99 fallback consistency/meson.build b/test cases/failing/99 fallback consistency/meson.build
new file mode 100644
index 0000000..362459c
--- /dev/null
+++ b/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'])
diff --git a/test cases/failing/99 fallback consistency/subprojects/sub/meson.build b/test cases/failing/99 fallback consistency/subprojects/sub/meson.build
new file mode 100644
index 0000000..12a6570
--- /dev/null
+++ b/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)
diff --git a/test cases/linuxlike/5 dependency versions/meson.build b/test cases/linuxlike/5 dependency versions/meson.build
index cb58a64..94f424d 100644
--- a/test cases/linuxlike/5 dependency versions/meson.build
+++ b/test cases/linuxlike/5 dependency versions/meson.build
@@ -71,18 +71,18 @@ 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 : ['somelib', 'some_dep'],
+  fallback : ['donotexist', 'fakezlib_dep'],
   required: false)
 assert(not d.found(), 'version should not match and it should not fallback')
 
diff --git a/test cases/linuxlike/5 dependency versions/subprojects/fakezlib/meson.build b/test cases/linuxlike/5 dependency versions/subprojects/fakezlib/meson.build
new file mode 100644
index 0000000..5a07763
--- /dev/null
+++ b/test cases/linuxlike/5 dependency versions/subprojects/fakezlib/meson.build
@@ -0,0 +1,3 @@
+project('some', 'c', version : '0.1')
+
+fakezlib_dep = declare_dependency()