adding more details into the error message during the CSV parser issues

Author: gbidsilva

src/main/java/org/apache/commons/csv/CSVParser.java

@@ -355,6 +355,8 @@ public static CSVParser parse(final URL url, final Charset charset, final CSVFor
         return new CSVParser(new InputStreamReader(url.openStream(), charset), format);
     }
 
+    private int maxParsedTokenCount = 5;
+
     private String headerComment;
 
     private String trailerComment;
@@ -440,6 +442,44 @@ public CSVParser(final Reader reader, final CSVFormat format, final long charact
         this.recordNumber = recordNumber - 1;
     }
 
+    /**
+     * Return the parsed CSV content of current reading line up until this method is called.
+     * <p>
+     * Maximum parsed token length set by the 'maxParsedTokenCount' is considered during the construction of return string.
+     * </p>
+     * <p>
+     * Example:
+     * </p>
+     * </p>
+     * If currently reading CSV record row contains following data and 'maxParsedTokenCount' is set to 5 and current reading position is col7
+     * </p>
+     * <pre>
+     * col1, col2, col3, col4, col5, col6, col7
+     * </pre>
+     * <p>
+     * then this would return following
+     * </p>
+     * <pre>
+     * col3, col4, col5, col6, col7
+     * </pre>
+     * @return parsed CSV content of current reading line
+     */
+    private String getLastParsedContent(){
+        String parsedContent = "";
+        int recordListSize = this.recordList.size();
+        if(recordListSize > 0) {
+            if(recordListSize <= this.maxParsedTokenCount) {
+                parsedContent = String.join("", this.recordList.toArray(Constants.EMPTY_STRING_ARRAY));
+            } else {
+                // number of parsed token exceed required token count. Take the expected tokens from the end.
+                int startIndex = recordListSize - maxParsedTokenCount;
+                List<String> lastParsedTokenList = this.recordList.subList(startIndex, recordListSize);
+                parsedContent = "..." + String.join(this.format.getDelimiterString(), lastParsedTokenList.toArray(Constants.EMPTY_STRING_ARRAY));
+            }
+        }
+        return parsedContent;
+    }
+
     private void addRecordValue(final boolean lastRecord) {
         final String input = this.format.trim(this.reusableToken.content.toString());
         if (lastRecord && input.isEmpty() && this.format.getTrailingDelimiter()) {
@@ -767,7 +807,15 @@ CSVRecord nextRecord() throws IOException {
         final long startCharPosition = lexer.getCharacterPosition() + this.characterOffset;
         do {
             this.reusableToken.reset();
-            this.lexer.nextToken(this.reusableToken);
+            // https://issues.apache.org/jira/browse/CSV-147
+            try{
+                this.lexer.nextToken(this.reusableToken);
+            } catch (IOException ioe){
+                String errorMessage = "An error occurred while tying to parse the CSV content. Error in line: "
+                        + this.lexer.getCurrentLineNumber() + ", position: " + this.lexer.getCharacterPosition()
+                        + ", last parsed content: " + this.getLastParsedContent();
+                throw new IOException(errorMessage, ioe);
+            }
             switch (this.reusableToken.type) {
             case TOKEN:
                 this.addRecordValue(false);

src/test/java/org/apache/commons/csv/CSVParserTest.java

@@ -1642,4 +1642,30 @@ private void validateRecordPosition(final String lineSeparator) throws IOExcepti
         parser.close();
     }
 
+    @Test
+    public void testFaultyCSVShouldThrowErrorWithDetailedMessage() {
+
+        String csvContent = "col1,col2,col3,col4,col5,col6,col7,col8,col9,col10\n" +
+                "rec1,rec2,rec3,rec4,rec5,rec6,rec7,rec8,\"\"rec9\"\",rec10";
+
+        StringReader stringReader = new StringReader(csvContent);
+        CSVFormat csvFormat = CSVFormat.DEFAULT.builder()
+                .setHeader()
+                .setSkipHeaderRecord(true)
+                .build();
+
+        Exception exception = assertThrows(UncheckedIOException.class, ()-> {
+            Iterable<CSVRecord> records = csvFormat.parse(stringReader);
+            for (CSVRecord record : records) {
+                System.out.println(record.get(0) + " " + record.get(1) + " " + record.get(2) + " " + record.get(3) + " " + record.get(4) + " " + record.get(5) + " " + record.get(6) + " " + record.get(7) + " " + record.get(8) + " " + record.get(9));
+            }
+        });
+        String expectedErrorMessage = "IOException reading next record: java.io.IOException: An error occurred while tying to parse the CSV content. Error in line: 2, position: 94, last parsed content: ...rec4,rec5,rec6,rec7,rec8";
+        String actualMessage = exception.getMessage();
+
+        assertTrue(actualMessage.contains(expectedErrorMessage));
+
+
+    }
+
 }