Fix docs_from_attrs truncating mid-UTF-8 codepoint

Cargo.toml

@@ -16,7 +16,7 @@ members = [
 
 [workspace.package]
 version = "25.3.0"
-rust-version = "1.84.0"
+rust-version = "1.91.0"
 
 [workspace.dependencies]
 soroban-sdk = { version = "25.3.0", path = "soroban-sdk" }

soroban-sdk-macros/src/doc.rs

@@ -20,9 +20,33 @@ pub fn docs_from_attrs(attrs: &[Attribute]) -> StringM<DOCS_MAX_LEN> {
             _ => None,
         })
         .map(|s| s.trim().to_string())
-        .join("\n")
-        .as_bytes()
-        .to_vec();
-    docs.truncate(DOCS_MAX_LEN as usize);
-    docs.try_into().unwrap()
+        .join("\n");
+    // Truncate on a char boundary to avoid splitting multi-byte UTF-8 codepoints.
+    let max = DOCS_MAX_LEN as usize;
+    let safe_len = docs.floor_char_boundary(max);
+    docs.truncate(safe_len);
+    docs.into_bytes().try_into().unwrap()
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use syn::parse_quote;
+
+    #[test]
+    fn test_truncation_does_not_split_multibyte_utf8() {
+        // (DOCS_MAX_LEN - 1) ASCII bytes followed by 'é' (2 bytes: 0xC3
+        // 0xA9) = DOCS_MAX_LEN + 1 bytes. Truncation at DOCS_MAX_LEN keeps
+        // the 0xC3 but drops the 0xA9, producing invalid UTF-8.
+        let padding = "a".repeat(DOCS_MAX_LEN as usize - 1);
+        let doc_value = format!("{padding}é");
+        let attr: Attribute = parse_quote!(#[doc = #doc_value]);
+        let result = docs_from_attrs(&[attr]);
+        let bytes: Vec<u8> = result.into();
+        assert!(
+            std::str::from_utf8(&bytes).is_ok(),
+            "truncation produced invalid UTF-8: trailing bytes {:?}",
+            &bytes[bytes.len().saturating_sub(4)..]
+        );
+    }
 }

soroban-sdk/test_snapshots/tests/address/test_get_existing_contract_address_executable_wasm.1.json

@@ -47,7 +47,7 @@
               "val": {
                 "contract_instance": {
                   "executable": {
-                    "wasm": "bace965b8cb8356bcb9ec67b78828f9f39379aa8be62c7a9982ce93c7d13eea4"
+                    "wasm": "8d628a321427edfff529b77997d15aaf6427664924d3173956c78abc76c0ca54"
                   },
                   "storage": null
                 }
@@ -68,11 +68,11 @@
                   "ext": "v0",
                   "cost_inputs": {
                     "ext": "v0",
-                    "n_instructions": 838,
-                    "n_functions": 9,
+                    "n_instructions": 801,
+                    "n_functions": 8,
                     "n_globals": 4,
                     "n_table_entries": 0,
-                    "n_types": 9,
+                    "n_types": 8,
                     "n_data_segments": 1,
                     "n_elem_segments": 0,
                     "n_imports": 7,
@@ -81,8 +81,8 @@
                   }
                 }
               },
-              "hash": "bace965b8cb8356bcb9ec67b78828f9f39379aa8be62c7a9982ce93c7d13eea4",
-              "code": 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+              "hash": "8d628a321427edfff529b77997d15aaf6427664924d3173956c78abc76c0ca54",
+              "code": 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             }
           },
           "ext": "v0"