Improve logged messages for overriden dependencies

3 files changed, 27 insertions, 12 deletions

diff --git a/docs/markdown/Reference-manual.md b/docs/markdown/Reference-manual.md
index b4d2333..9bb7911 100644
--- a/docs/markdown/Reference-manual.md
+++ b/docs/markdown/Reference-manual.md
@@ -1839,7 +1839,10 @@ the following methods.
   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()`.
+  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.
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 33820b4..2b5c0ea 100644
--- a/mesonbuild/build.py
+++ b/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.
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index b3789c3..c247e63 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -2022,17 +2022,20 @@ class MesonMain(InterpreterObject):
         name = args[0]
         dep = args[1]
         if not isinstance(name, str) or not name:
-            raise InterpreterException('First argument must be not empty string')
+            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)
-        if identifier in self.build.dependency_overrides[for_machine]:
-            raise InterpreterException('Tried to override dependency "%s" which has already been overridden.'
-                                       % name)
-        self.build.dependency_overrides[for_machine][identifier] = dep
+        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({})
@@ -3242,14 +3245,16 @@ external dependencies (including libraries) must go to "dependencies".''')
         identifier = dependencies.get_dep_identifier(name, kwargs)
         wanted_vers = mesonlib.stringlistify(kwargs.get('version', []))
 
-        cached_dep = self.build.dependency_overrides[for_machine].get(identifier)
-        if cached_dep:
+        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
             found_vers = cached_dep.get_version()
             if not self.check_version(wanted_vers, found_vers):
@@ -3257,9 +3262,10 @@ external dependencies (including libraries) must go to "dependencies".''')
                          'found:', mlog.red('NO'),
                          'found', mlog.normal_cyan(found_vers), 'but need:',
                          mlog.bold(', '.join(["'{}'".format(e) for e in wanted_vers])),
-                         mlog.blue('(cached)'))
+                         *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()
@@ -3267,7 +3273,6 @@ external dependencies (including libraries) must go to "dependencies".''')
                     return identifier, None
 
         if cached_dep:
-            info = [mlog.blue('(cached)')]
             if found_vers:
                 info = [mlog.normal_cyan(found_vers), *info]
             mlog.log('Dependency', mlog.bold(name),
@@ -3383,7 +3388,8 @@ external dependencies (including libraries) must go to "dependencies".''')
             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] = d.held_object
+                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):