rust: Add linkdirs of indirect Rust dependencies to the target's link…

…dirs

rustc requires all the linkdirs to indirect dependencies to be able to
find them, but doesn't require them to be provided as `--extern` in
addition. The latter would also easily lead to name conflicts.

Fixes #11694

mesonbuild/backend/ninjabackend.py

@@ -1836,6 +1836,27 @@ def _get_rust_dependency_name(self, target: build.BuildTarget, dependency: LibTy
         # in Rust
         return target.rust_dependency_map.get(dependency.name, dependency.name).replace('-', '_')
 
+    def _add_rust_indirect_dependency_linkdirs(self, linkdirs: OrderedSet[str], dependency: LibTypes):
+        # Add all the linkdirs of indirect dependencies to the linkdirs if
+        # they're rlib/proc-macro/dylib dependencies. rustc requires this to
+        # be able to find the indirect dependencies during the build.
+        indirect_rust_deps = [dependency]
+
+        # Instead of actually recursing over the dependencies use a stack here
+        while indirect_rust_deps:
+            indirect_dep = indirect_rust_deps.pop()
+            if not indirect_dep.uses_rust() or indirect_dep.rust_crate_type in ['staticlib', 'cdylib']:
+                continue
+            for d in indirect_dep.kwargs.get('dependencies', []):
+                if not hasattr(d, 'libraries'):
+                    continue
+                indirect_rust_deps += d.libraries
+                indirect_rust_deps += d.whole_libraries
+            indirect_rust_deps += indirect_dep.link_targets
+            indirect_rust_deps += indirect_dep.link_whole_targets
+
+            linkdirs.add(indirect_dep.subdir)
+
     def generate_rust_target(self, target: build.BuildTarget) -> None:
         rustc = target.compilers['rust']
         # Rust compiler takes only the main file as input and
@@ -1945,6 +1966,7 @@ def generate_rust_target(self, target: build.BuildTarget) -> None:
                 d_name = self._get_rust_dependency_name(target, d)
                 args += ['--extern', '{}={}'.format(d_name, os.path.join(d.subdir, d.filename))]
                 project_deps.append(RustDep(d_name, self.rust_crates[d.name].order))
+                self._add_rust_indirect_dependency_linkdirs(linkdirs, d)
             elif isinstance(d, build.StaticLibrary):
                 # Rustc doesn't follow Meson's convention that static libraries
                 # are called .a, and import libraries are .lib, so we have to
@@ -1984,6 +2006,7 @@ def generate_rust_target(self, target: build.BuildTarget) -> None:
                 d_name = self._get_rust_dependency_name(target, d)
                 args += ['--extern', '{}={}'.format(d_name, os.path.join(d.subdir, d.filename))]
                 project_deps.append(RustDep(d_name, self.rust_crates[d.name].order))
+                self._add_rust_indirect_dependency_linkdirs(linkdirs, d)
             else:
                 if rustc.linker.id in {'link', 'lld-link'}:
                     if verbatim:

test cases/rust/20 transitive dependencies/liba/lib.rs

@@ -0,0 +1,3 @@
+pub fn foo() -> i32 {
+    123
+}

test cases/rust/20 transitive dependencies/liba/meson.build

@@ -0,0 +1,5 @@
+liba = static_library('liba', 'lib.rs',
+  rust_crate_type : 'rlib',
+)
+
+liba_dep = declare_dependency(link_with : liba)

test cases/rust/20 transitive dependencies/libb/lib.rs

@@ -0,0 +1,3 @@
+pub fn bar() -> i32 {
+    2 * liba::foo()
+}

test cases/rust/20 transitive dependencies/libb/meson.build

@@ -0,0 +1,6 @@
+libb = static_library('libb', 'lib.rs',
+  rust_crate_type : 'rlib',
+  dependencies : [liba_dep],
+)
+
+libb_dep = declare_dependency(link_with : libb)

test cases/rust/20 transitive dependencies/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("{}", libb::bar());
+}

test cases/rust/20 transitive dependencies/meson.build

@@ -0,0 +1,12 @@
+project('transitive dependencies', 'rust',
+  version : '1.0.0',
+  meson_version : '>= 1.0.0',
+  default_options : ['rust_std=2018'],
+)
+
+subdir('liba')
+subdir('libb')
+
+main = executable('main', 'main.rs',
+  dependencies : [libb_dep],
+)