Merge pull request #316 from rainlanguage/2026-09-02-issue-203

cbor_decode requires the rain meta document prefix

Author: thedavidmeister

crates/cli/src/error/mod.rs

@@ -8,6 +8,7 @@ use crate::meta::KnownMagic;
 #[derive(Debug)]
 pub enum Error {
     CorruptMeta,
+    NotRainMetaDocument,
     InvalidHash,
     UnknownMeta,
     UnknownMagic,
@@ -36,6 +37,9 @@ impl std::fmt::Display for Error {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
             Error::CorruptMeta => f.write_str("corrupt meta"),
+            Error::NotRainMetaDocument => f.write_str(
+                "not a rain meta document: the bytes do not begin with the rain meta magic number",
+            ),
             Error::UnknownMeta => f.write_str("unknown meta"),
             Error::UnknownMagic => f.write_str("unknown magic"),
             Error::UnsupportedMeta => f.write_str("unsupported meta"),
@@ -117,6 +121,10 @@ mod tests {
     #[test]
     fn test_display_fixed_strings() {
         assert_eq!(Error::CorruptMeta.to_string(), "corrupt meta");
+        assert_eq!(
+            Error::NotRainMetaDocument.to_string(),
+            "not a rain meta document: the bytes do not begin with the rain meta magic number"
+        );
         assert_eq!(Error::UnknownMeta.to_string(), "unknown meta");
         assert_eq!(Error::UnknownMagic.to_string(), "unknown magic");
         assert_eq!(Error::UnsupportedMeta.to_string(), "unsupported meta");

crates/cli/src/lib.rs

@@ -58,10 +58,14 @@
 //!   schema: None,
 //! };
 //!
-//! // cbor encode the meta item
-//! let cbor_encoded = meta_map.cbor_encode().unwrap();
+//! // cbor encode the meta item as a rain meta document: the document magic
+//! // number prefix, then the item. The decoder requires that prefix.
+//! let cbor_encoded = RainMetaDocumentV1Item::cbor_encode_seq(
+//!     &vec![meta_map],
+//!     KnownMagic::RainMetaDocumentV1,
+//! ).unwrap();
 //!
-//! // decode the data back
+//! // decode the document back
 //! let cbor_decoded_vec = RainMetaDocumentV1Item::cbor_decode(&cbor_encoded).unwrap();
 //!
 //! // unpack the payload into AuthoringMeta