Improve error mesage on save, add current field content (JabRef#4710)

* Improve error mesage on save, add current field content

* fix spaces around plus sign

* fix formatting

src/main/java/org/jabref/logic/bibtex/LatexFieldFormatter.java

@@ -23,7 +23,6 @@ public class LatexFieldFormatter {
  private final FieldContentParser parser;
  private StringBuilder stringBuilder;
 
-
  public LatexFieldFormatter(LatexFieldFormatterPreferences prefs) {
  this(true, prefs);
  }
@@ -48,26 +47,26 @@ private static void checkBraces(String text) throws InvalidFieldValueException {
  char item = text.charAt(i);
 
  boolean charBeforeIsEscape = false;
- if (i > 0 && text.charAt(i - 1) == '\\') {
+ if ((i > 0) && (text.charAt(i - 1) == '\\')) {
  charBeforeIsEscape = true;
  }
 
- if (!charBeforeIsEscape && item == '{') {
+ if (!charBeforeIsEscape && (item == '{')) {
  left++;
- } else if (!charBeforeIsEscape && item == '}') {
+ } else if (!charBeforeIsEscape && (item == '}')) {
  right++;
  }
  }
 
  // Then we throw an exception if the error criteria are met.
  if (!(right == 0) && (left == 0)) {
- throw new InvalidFieldValueException("Unescaped '}' character without opening bracket ends string prematurely.");
+ throw new InvalidFieldValueException("Unescaped '}' character without opening bracket ends string prematurely. Field value: " + text);
  }
  if (!(right == 0) && (right < left)) {
- throw new InvalidFieldValueException("Unescaped '}' character without opening bracket ends string prematurely.");
+ throw new InvalidFieldValueException("Unescaped '}' character without opening bracket ends string prematurely. Field value: " + text);
  }
  if (left != right) {
- throw new InvalidFieldValueException("Braces don't match.");
+ throw new InvalidFieldValueException("Braces don't match. Field value: " + text);
  }
  }
 
@@ -146,9 +145,9 @@ private String formatAndResolveStrings(String content, String fieldName) throws
  pos1 = content.length(); // just write out the rest of the text, and throw no exception
  } else {
  throw new InvalidFieldValueException(
- "The # character is not allowed in BibTeX strings unless escaped as in '\\#'.\n"
- + "In JabRef, use pairs of # characters to indicate a string.\n"
- + "Note that the entry causing the problem has been selected.");
+  "The # character is not allowed in BibTeX strings unless escaped as in '\\#'.\n"
+  + "In JabRef, use pairs of # characters to indicate a string.\n"
+  + "Note that the entry causing the problem has been selected. Field value: " + content);
  }
  }
  }
@@ -161,7 +160,7 @@ private String formatAndResolveStrings(String content, String fieldName) throws
  // an occurrence of ## will simply be ignored. Should it instead
  // cause an error message?
  writeStringLabel(content, pos1 + 1, pos2, pos1 == pivot,
- (pos2 + 1) == content.length());
+  (pos2 + 1) == content.length());
  }
 
  if (pos2 > -1) {
@@ -187,16 +186,15 @@ private boolean shouldResolveStrings(String fieldName) {
  } else {
  // Default operation - we only resolve strings for standard fields:
  resolveStrings = InternalBibtexFields.isStandardField(fieldName)
- || BIBTEX_STRING.equals(fieldName);
+  || BIBTEX_STRING.equals(fieldName);
  }
  return resolveStrings;
  }
 
  private String formatWithoutResolvingStrings(String content, String fieldName) throws InvalidFieldValueException {
  checkBraces(content);
 
- stringBuilder = new StringBuilder(
- String.valueOf(FIELD_START));
+ stringBuilder = new StringBuilder(String.valueOf(FIELD_START));
 
  stringBuilder.append(parser.format(content, fieldName));
 
@@ -258,7 +256,7 @@ private void writeText(String text, int startPos, int endPos) {
  // We add a backslash before any ampersand characters, with one exception: if
  // we are inside an \\url{...} command, we should write it as it is. Maybe.
  if ((c == '&') && !escape && !(inCommand && "url".equals(commandName.toString()))
-  && (nestedEnvironments == 0)) {
+ && (nestedEnvironments == 0)) {
  stringBuilder.append("\\&");
  } else {
  stringBuilder.append(c);
@@ -271,7 +269,7 @@ private void writeText(String text, int startPos, int endPos) {
  private void writeStringLabel(String text, int startPos, int endPos,
  boolean first, boolean last) {
  putIn((first ? "" : " # ") + text.substring(startPos, endPos)
-  + (last ? "" : " # "));
+ + (last ? "" : " # "));
  }
 
  private void putIn(String s) {