Fix custom_metadata bug for Crossref export

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Fixed
+  - [679](https://github.com/thoth-pub/thoth/issues/679) - Remove extraneous <custom_metadata> tag from Crossmark block in Crossref DOI deposit export when an Imprint has recorded a Crossmark DOI but a Work has no license or funding metadata.
 
 ## [[0.13.8]](https://github.com/thoth-pub/thoth/releases/tag/v0.13.8) - 2025-03-26
 ### Added

thoth-app/src/component/mod.rs

@@ -399,10 +399,7 @@ impl ToOption for String {
     }
 
     fn to_opt_date(self) -> Option<chrono::NaiveDate> {
-        match chrono::NaiveDate::parse_from_str(&self, "%Y-%m-%d") {
-            Ok(date) => Some(date),
-            Err(_) => None,
-        }
+        chrono::NaiveDate::parse_from_str(&self, "%Y-%m-%d").ok()
     }
 }
 

thoth-app/src/service/account.rs

@@ -37,11 +37,7 @@ impl AccountService {
     }
 
     pub fn get_token(&self) -> Option<String> {
-        if let Ok(token) = LocalStorage::get(SESSION_KEY) {
-            Some(token)
-        } else {
-            None
-        }
+        LocalStorage::get(SESSION_KEY).ok()
     }
 
     pub fn set_token(&self, token: String) {

thoth-export-server/src/xml/doideposit_crossref.rs

@@ -485,8 +485,12 @@ fn write_crossmark_funding_access<W: Write>(
             }
 
             // If crossmark metadata is included, funding and access data must be inside the <crossmark> element
-            // within <custom_metadata> tag
-            write_element_block("custom_metadata", w, |w| write_work_funding_access(work, w))
+            // within <custom_metadata> tag. If no funding or access data exist, don't include <custom_metadata> tag.
+            if work.license.is_some() || !work.fundings.is_empty() {
+                write_element_block("custom_metadata", w, |w| write_work_funding_access(work, w))
+            } else {
+                Ok(())
+            }
         })?;
     // If no crossmark metadata, funding and access data go here
     } else {