From 192dffb2693d0d5f47d7326214b2ab7d1a20b305 Mon Sep 17 00:00:00 2001
From: Siedlerchr <siedlerkiller@gmail.com>
Date: Wed, 24 May 2023 20:10:27 +0200
Subject: [PATCH] Fix unmodifable Set Exception in generating preview

Add hint in javadoc

Fixes #9947
Fixes https://github.com/JabRef/jabref-issue-melting-pot/issues/183
---
 CHANGELOG.md                                                | 1 +
 .../jabref/logic/citationstyle/JabRefItemDataProvider.java  | 3 ++-
 src/main/java/org/jabref/model/entry/BibEntry.java          | 6 +++---
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 894ddc88497..7812dc5e370 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -90,6 +90,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 - We fixed an issue in the preferences where custom columns could be added to the entry table with no qualifier. [#9913](https://github.com/JabRef/jabref/issues/9913)
 - We fixed an issue where the encoding header in a bib file was not respected when the file contained a BOM (Byte Order Mark). [#9926](https://github.com/JabRef/jabref/issues/9926)
 - We fixed an issue where cli help output for import and export format was inconsistent. [koppor#429](https://github.com/koppor/jabref/issues/429)
+- We fixed an issue where no preview could be generated for some entry types and led to an exception [#9947](https://github.com/JabRef/jabref/issues/9947)
 
 ### Removed
 
diff --git a/src/main/java/org/jabref/logic/citationstyle/JabRefItemDataProvider.java b/src/main/java/org/jabref/logic/citationstyle/JabRefItemDataProvider.java
index b15c0e4534a..e75b4e7b3a9 100644
--- a/src/main/java/org/jabref/logic/citationstyle/JabRefItemDataProvider.java
+++ b/src/main/java/org/jabref/logic/citationstyle/JabRefItemDataProvider.java
@@ -2,6 +2,7 @@
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Optional;
@@ -147,7 +148,7 @@ private CSLItemData bibEntryToCSLItemData(BibEntry originalBibEntry, BibDatabase
             }
         }
 
-        Set<Field> fields = entryType.map(BibEntryType::getAllFields).orElse(bibEntry.getFields());
+        Set<Field> fields = new LinkedHashSet<>(entryType.map(BibEntryType::getAllFields).orElse(bibEntry.getFields()));
         fields.addAll(bibEntry.getFields());
         for (Field key : fields) {
             bibEntry.getResolvedFieldOrAlias(key, bibDatabaseContext.getDatabase())
diff --git a/src/main/java/org/jabref/model/entry/BibEntry.java b/src/main/java/org/jabref/model/entry/BibEntry.java
index 4718ab3645a..29873c4d9c2 100644
--- a/src/main/java/org/jabref/model/entry/BibEntry.java
+++ b/src/main/java/org/jabref/model/entry/BibEntry.java
@@ -313,7 +313,7 @@ public Optional<String> getResolvedFieldOrAliasLatexFree(Field field, BibDatabas
     }
 
     private Optional<String> genericGetResolvedFieldOrAlias(Field field, BibDatabase database, BiFunction<BibEntry, Field, Optional<String>> getFieldOrAlias) {
-        if (InternalField.TYPE_HEADER == field || InternalField.OBSOLETE_TYPE_HEADER == field) {
+        if ((InternalField.TYPE_HEADER == field) || (InternalField.OBSOLETE_TYPE_HEADER == field)) {
             return Optional.of(type.get().getDisplayName());
         }
 
@@ -434,7 +434,7 @@ public Optional<FieldChange> setType(EntryType newType, EntriesEventSource event
     }
 
     /**
-     * Returns a set containing the names of all fields that are set for this particular entry.
+     * Returns an {@link Collections#unmodifiableSet(Set)} containing the names of all fields that are set for this particular entry.
      *
      * @return a set of existing field names
      */
@@ -489,7 +489,7 @@ private Optional<String> genericGetFieldOrAlias(Field field, BiFunction<BibEntry
             return date.map(Date::getNormalized);
         }
 
-        if (StandardField.YEAR == field || StandardField.MONTH == field || StandardField.DAY == field) {
+        if ((StandardField.YEAR == field) || (StandardField.MONTH == field) || (StandardField.DAY == field)) {
             Optional<String> date = getFieldValue.apply(this, StandardField.DATE);
             if (date.isEmpty()) {
                 return Optional.empty();