Enforce correct rust library file names.

rustc expects libraries and proc_macro filenames to conform to
a particular format, alphanumeric with underscores and lib${crate_name}.*.
Enforce this with a check when getStem() is called.

This makes the crate_name property required for proc_macros and
libraries. This also removes the notion of a default crate name derived
from the module name. It's not needed for binaries, so this won't impact
them.

Bug: 143579265
Test: m -j crosvm.experimental
Change-Id: I2770cf7d02dd4291c3d240d58d242b940098dcee

rust/library_test.go

@@ -77,3 +77,40 @@ func TestDylibPreferDynamic(t *testing.T) {
 		t.Errorf("missing prefer-dynamic flag for libfoo dylib, rustcFlags: %#v", libfooDylib.Args["rustcFlags"])
 	}
 }
+
+func TestValidateLibraryStem(t *testing.T) {
+	testRustError(t, "crate_name must be defined.", `
+			rust_library_host {
+				name: "libfoo",
+				srcs: ["foo.rs"],
+			}`)
+
+	testRustError(t, "library crate_names must be alphanumeric with underscores allowed", `
+			rust_library_host {
+				name: "libfoo-bar",
+				srcs: ["foo.rs"],
+				crate_name: "foo-bar"
+			}`)
+
+	testRustError(t, "Invalid name or stem property; library filenames must start with lib<crate_name>", `
+			rust_library_host {
+				name: "foobar",
+				srcs: ["foo.rs"],
+				crate_name: "foo_bar"
+			}`)
+	testRustError(t, "Invalid name or stem property; library filenames must start with lib<crate_name>", `
+			rust_library_host {
+				name: "foobar",
+				stem: "libfoo",
+				srcs: ["foo.rs"],
+				crate_name: "foo_bar"
+			}`)
+	testRustError(t, "Invalid name or stem property; library filenames must start with lib<crate_name>", `
+			rust_library_host {
+				name: "foobar",
+				stem: "foo_bar",
+				srcs: ["foo.rs"],
+				crate_name: "foo_bar"
+			}`)
+
+}