Consider compile_data when deciding if sources are generated

This fixes issue where generated compile_data didn't work in some cases.

rust/private/utils.bzl

@@ -811,7 +811,11 @@ def transform_sources(ctx, srcs, compile_data, crate_root):
         Tuple(List[File], List[File], File): The transformed srcs, compile_data
                                              and crate_root
     """
-    has_generated_sources = len([src for src in srcs if not src.is_source]) > 0
+    has_generated_sources = (
+        len([src for src in srcs if not src.is_source])
+        + len([src for src in compile_data if not src.is_source])
+        > 0
+    )
 
     if not has_generated_sources:
         return srcs, compile_data, crate_root

test/unit/compile_data/compile_data_gen.rs

@@ -0,0 +1,12 @@
+/// Data loaded from generated compile data
+pub const COMPILE_DATA: &str = include_str!("generated.txt");
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_compile_data_contents() {
+        assert_eq!(COMPILE_DATA.trim_end(), "generated compile data contents");
+    }
+}

test/unit/compile_data/compile_data_test.bzl

@@ -95,6 +95,24 @@ def _define_test_targets():
         crate = ":compile_data_env",
     )
 
+    native.genrule(
+        name = "generated_compile_data",
+        outs = ["generated.txt"],
+        cmd = "echo 'generated compile data contents' > $@",
+    )
+
+    rust_library(
+        name = "compile_data_gen",
+        srcs = ["compile_data_gen.rs"],
+        compile_data = [":generated.txt"],
+        edition = "2021",
+    )
+
+    rust_test(
+        name = "compile_data_gen_unit_test",
+        crate = ":compile_data_gen",
+    )
+
     native.genrule(
         name = "generated_src",
         outs = ["generated.rs"],