Support module discovery for lib.rs crate roots

generation_tests/deleted_file/BUILD.in

@@ -0,0 +1,9 @@
+load("@rules_rust//rust:defs.bzl", "rust_library")
+
+rust_library(
+    name = "lib",
+    srcs = [
+        "deleted.rs",
+        "lib.rs",
+    ],
+)

generation_tests/deleted_file/BUILD.out

@@ -0,0 +1,6 @@
+load("@rules_rust//rust:defs.bzl", "rust_library")
+
+rust_library(
+    name = "lib",
+    srcs = ["lib.rs"],
+)

generation_tests/deleted_file/README.md

@@ -0,0 +1,2 @@
+
+Files that no longer exist on disk are removed from existing rules.

generation_tests/deleted_file/lib.rs

@@ -0,0 +1 @@
+pub fn lib() {}

generation_tests/module_discovery/BUILD.out

@@ -0,0 +1,11 @@
+load("@rules_rust//rust:defs.bzl", "rust_library")
+
+rust_library(
+    name = "lib",
+    srcs = [
+        "bar.rs",
+        "foo.rs",
+        "lib.rs",
+    ],
+    crate_root = "lib.rs",
+)

generation_tests/module_discovery/README.md

@@ -0,0 +1,2 @@
+
+lib.rs crate roots discover their modules via mod declarations.

generation_tests/module_discovery/bar.rs

@@ -0,0 +1 @@
+pub fn bar() {}

generation_tests/module_discovery/foo.rs

@@ -0,0 +1 @@
+pub fn foo() {}

generation_tests/module_discovery/lib.rs

@@ -0,0 +1,2 @@
+mod foo;
+mod bar;

generation_tests/subdir_module/BUILD.out

@@ -0,0 +1,10 @@
+load("@rules_rust//rust:defs.bzl", "rust_library")
+
+rust_library(
+    name = "lib",
+    srcs = [
+        "lib.rs",
+        "subdir/mod.rs",
+    ],
+    crate_root = "lib.rs",
+)

generation_tests/subdir_module/README.md

@@ -0,0 +1,9 @@
+
+When lib.rs declares `mod subdir;` pointing to subdir/mod.rs, the module file
+should be included in the parent crate's srcs and NOT get its own rust_library
+target in the subdirectory.
+
+This tests that:
+1. lib.rs crate roots discover modules in subdirectories.
+2. Subdirectory BUILD files don't create rust rules for files claimed by a parent crate.
+3. Unclaimed files in the subdirectory still get their own rules.

generation_tests/subdir_module/lib.rs

@@ -0,0 +1,3 @@
+mod subdir;
+
+pub use subdir::greet;

generation_tests/subdir_module/subdir/BUILD.out

@@ -0,0 +1,6 @@
+load("@rules_rust//rust:defs.bzl", "rust_test")
+
+rust_test(
+    name = "standalone_test",
+    srcs = ["standalone_test.rs"],
+)

generation_tests/subdir_module/subdir/mod.rs

@@ -0,0 +1,3 @@
+pub fn greet() -> &'static str {
+    "Hello from subdir module"
+}

generation_tests/subdir_module/subdir/standalone_test.rs

@@ -0,0 +1,4 @@
+#[test]
+fn test_standalone() {
+    assert!(true);
+}

generation_tests/subdir_module_adjacent/BUILD.out

@@ -0,0 +1,12 @@
+load("@rules_rust//rust:defs.bzl", "rust_library")
+
+rust_library(
+    name = "lib",
+    srcs = [
+        "lib.rs",
+        "parent.rs",
+        "parent/child.rs",
+        "parent/child/grandchild.rs",
+    ],
+    crate_root = "lib.rs",
+)

generation_tests/subdir_module_adjacent/README.md

@@ -0,0 +1,14 @@
+
+Tests the adjacent file module style (introduced in Rust 2018) where modules use
+parent.rs instead of parent/mod.rs.
+
+Structure:
+- lib.rs declares `mod parent;`
+- parent.rs (adjacent file style) declares `mod child;`
+- parent/child.rs declares `mod grandchild;`
+- parent/child/grandchild.rs is claimed by the root lib.rs crate
+
+This tests that:
+1. Adjacent file module discovery works (parent.rs instead of parent/mod.rs).
+2. Deeply nested modules are correctly claimed through intermediate adjacent-style modules.
+3. Unclaimed files in subdirectories still get their own rules.

generation_tests/subdir_module_adjacent/lib.rs

@@ -0,0 +1,3 @@
+mod parent;
+
+pub use parent::greet;

generation_tests/subdir_module_adjacent/parent.rs

@@ -0,0 +1,4 @@
+mod child;
+
+pub use child::greet;
+pub use child::nested_greet;

generation_tests/subdir_module_adjacent/parent/BUILD.out

@@ -0,0 +1,11 @@
+load("@rules_rust//rust:defs.bzl", "rust_library", "rust_test")
+
+rust_test(
+    name = "standalone_test",
+    srcs = ["standalone_test.rs"],
+)
+
+rust_library(
+    name = "util",
+    srcs = ["util.rs"],
+)

generation_tests/subdir_module_adjacent/parent/child.rs

@@ -0,0 +1,7 @@
+mod grandchild;
+
+pub use grandchild::nested_greet;
+
+pub fn greet() -> &'static str {
+    "Hello from child module"
+}

generation_tests/subdir_module_adjacent/parent/child/BUILD.out

@@ -0,0 +1,6 @@
+load("@rules_rust//rust:defs.bzl", "rust_test")
+
+rust_test(
+    name = "standalone_test",
+    srcs = ["standalone_test.rs"],
+)

generation_tests/subdir_module_adjacent/parent/child/grandchild.rs

@@ -0,0 +1,3 @@
+pub fn nested_greet() -> &'static str {
+    "Hello from grandchild module"
+}

generation_tests/subdir_module_adjacent/parent/child/standalone_test.rs

@@ -0,0 +1,4 @@
+#[test]
+fn test_deep_standalone() {
+    assert!(true);
+}

generation_tests/subdir_module_adjacent/parent/standalone_test.rs

@@ -0,0 +1,4 @@
+#[test]
+fn test_standalone() {
+    assert!(true);
+}

generation_tests/subdir_module_adjacent/parent/util.rs

@@ -0,0 +1,3 @@
+pub fn helper() -> i32 {
+    42
+}