dependencies: Fix caching of native/cross dependencies

All our cached_dep magic was totally useless since we ended up using
the same identifier for native and cross deps. Just nuke all this
cached_dep code since it is very error-prone and improve the
identifier generation instead.

For instance, this is broken *right now* with the `type_name` kwarg.

Add a bunch of tests to ensure that all this actually works...

Closes https://github.com/mesonbuild/meson/issues/1736

2 files changed, 15 insertions, 23 deletions

diff --git a/mesonbuild/dependencies.py b/mesonbuild/dependencies.py
index 37e2cbd..2267492 100644
--- a/mesonbuild/dependencies.py
+++ b/mesonbuild/dependencies.py
@@ -1742,21 +1742,17 @@ class LLVMDependency(Dependency):
         return True
 
 
-def get_dep_identifier(name, kwargs):
-    elements = [name]
-    modlist = kwargs.get('modules', [])
-    if isinstance(modlist, str):
-        modlist = [modlist]
-    for module in modlist:
-        elements.append(module)
-    # We use a tuple because we need a non-mutable structure to use as the key
-    # of a dictionary and a string has potential for name collisions
-    identifier = tuple(elements)
-    identifier += ('main', kwargs.get('main', False))
-    identifier += ('static', kwargs.get('static', False))
-    if 'fallback' in kwargs:
-        f = kwargs.get('fallback')
-        identifier += ('fallback', f[0], f[1])
+def get_dep_identifier(name, kwargs, want_cross):
+    # Need immutable objects since the identifier will be used as a dict key
+    identifier = (name, want_cross)
+    for key, value in kwargs.items():
+        # Ignore versions, they will be handled by the caller
+        if key == 'version':
+            continue
+        # All keyword arguments are strings, ints, or lists (or lists of lists)
+        if isinstance(value, list):
+            value = frozenset(mesonlib.flatten(value))
+        identifier += (key, value)
     return identifier
 
 def find_external_dependency(name, environment, kwargs):
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index 80d482e..886f200 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -1858,7 +1858,6 @@ class Interpreter(InterpreterBase):
         if '<' in name or '>' in name or '=' in name:
             raise InvalidArguments('Characters <, > and = are forbidden in dependency names. To specify'
                                    'version\n requirements use the \'version\' keyword argument instead.')
-        identifier = dependencies.get_dep_identifier(name, kwargs)
         # Check if we want this as a cross-dep or a native-dep
         # FIXME: Not all dependencies support such a distinction right now,
         # and we repeat this check inside dependencies that do. We need to
@@ -1868,10 +1867,14 @@ class Interpreter(InterpreterBase):
             want_cross = not kwargs['native']
         else:
             want_cross = is_cross
+        identifier = dependencies.get_dep_identifier(name, kwargs, want_cross)
         # Check if we've already searched for and found this dep
         cached_dep = None
         if identifier in self.coredata.deps:
             cached_dep = self.coredata.deps[identifier]
+            # All other kwargs are handled in get_dep_identifier(). We have
+            # this here as a tiny optimization to avoid searching for
+            # dependencies that we already have.
             if 'version' in kwargs:
                 wanted = kwargs['version']
                 found = cached_dep.get_version()
@@ -1880,13 +1883,6 @@ class Interpreter(InterpreterBase):
                     # Cached dep has the wrong version. Check if an external
                     # dependency or a fallback dependency provides it.
                     cached_dep = None
-            # Don't re-use cached dep if it wasn't required but this one is,
-            # so we properly go into fallback/error code paths
-            if kwargs.get('required', True) and not getattr(cached_dep, 'required', False):
-                cached_dep = None
-            # Don't reuse cached dep if one is a cross-dep and the other is a native dep
-            if not getattr(cached_dep, 'want_cross', is_cross) == want_cross:
-                cached_dep = None
 
         if cached_dep:
             dep = cached_dep