From 8f98cf634effa7a1b7600d45c58303a77610521f Mon Sep 17 00:00:00 2001
From: Igor Kamyshnikov <Igor.Kamyshnikov@fiducia.eco>
Date: Fri, 5 Apr 2024 17:59:01 +0100
Subject: [PATCH 1/2] MongoDBCsv empty first column parsing fix

---
 .../java/org/apache/commons/csv/Lexer.java    | 24 +++++++--------
 .../org/apache/commons/csv/CSVParserTest.java | 29 +++++++++++++++++++
 2 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/src/main/java/org/apache/commons/csv/Lexer.java b/src/main/java/org/apache/commons/csv/Lexer.java
index 17113227..80bde6c7 100644
--- a/src/main/java/org/apache/commons/csv/Lexer.java
+++ b/src/main/java/org/apache/commons/csv/Lexer.java
@@ -334,18 +334,7 @@ final class Lexer implements Closeable {
         while (true) {
             c = reader.read();
 
-            if (isEscape(c)) {
-                if (isEscapeDelimiter()) {
-                    token.content.append(delimiter);
-                } else {
-                    final int unescaped = readEscape();
-                    if (unescaped == EOF) { // unexpected char after escape
-                        token.content.append((char) c).append((char) reader.getLastChar());
-                    } else {
-                        token.content.append((char) unescaped);
-                    }
-                }
-            } else if (isQuoteChar(c)) {
+            if (isQuoteChar(c)) {
                 if (isQuoteChar(reader.lookAhead())) {
                     // double or escaped encapsulator -> add single encapsulator to token
                     c = reader.read();
@@ -376,6 +365,17 @@ final class Lexer implements Closeable {
                         }
                     }
                 }
+            } else if (isEscape(c)) {
+                if (isEscapeDelimiter()) {
+                    token.content.append(delimiter);
+                } else {
+                    final int unescaped = readEscape();
+                    if (unescaped == EOF) { // unexpected char after escape
+                        token.content.append((char) c).append((char) reader.getLastChar());
+                    } else {
+                        token.content.append((char) unescaped);
+                    }
+                }
             } else if (isEndOfFile(c)) {
                 if (lenientEof) {
                     token.type = Token.Type.EOF;
diff --git a/src/test/java/org/apache/commons/csv/CSVParserTest.java b/src/test/java/org/apache/commons/csv/CSVParserTest.java
index b3a51378..c0f497f7 100644
--- a/src/test/java/org/apache/commons/csv/CSVParserTest.java
+++ b/src/test/java/org/apache/commons/csv/CSVParserTest.java
@@ -1562,6 +1562,35 @@ public class CSVParserTest {
             assertEquals(3, record.size());
         }}
 
+    @Test
+    public void testParsingPrintedEmptyFirstColumn() throws Exception {
+        Exception firstException = null;
+        for (CSVFormat.Predefined format : CSVFormat.Predefined.values()) {
+            try {
+                StringWriter buf = new StringWriter();
+                try (CSVPrinter printer = new CSVPrinter(buf, format.getFormat())) {
+                    printer.printRecord("a", "b"); // header
+                    printer.printRecord("", "x");  // empty first column
+                }
+                try (CSVParser csvRecords = new CSVParser(new StringReader(buf.toString()), format.getFormat().builder().setHeader().build())) {
+                    for (CSVRecord csvRecord : csvRecords) {
+                        assertNotNull(csvRecord);
+                    }
+                }
+            } catch (Exception | Error e) {
+                Exception detailedException = new RuntimeException("format: " + format, e);
+                if (firstException == null) {
+                    firstException = detailedException;
+                } else {
+                    firstException.addSuppressed(detailedException);
+                }
+            }
+        }
+
+        if (firstException != null)
+            throw firstException;
+    }
+
     private void validateLineNumbers(final String lineSeparator) throws IOException {
         try (final CSVParser parser = CSVParser.parse("a" + lineSeparator + "b" + lineSeparator + "c", CSVFormat.DEFAULT.withRecordSeparator(lineSeparator))) {
             assertEquals(0, parser.getCurrentLineNumber());

From df7c340e7be5f662e641e911f1d5c76685abeaba Mon Sep 17 00:00:00 2001
From: Igor Kamyshnikov <Igor.Kamyshnikov@fiducia.eco>
Date: Fri, 5 Apr 2024 20:27:43 +0100
Subject: [PATCH 2/2] better test - comparing printer input and parser output

---
 .../org/apache/commons/csv/CSVParserTest.java  | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/test/java/org/apache/commons/csv/CSVParserTest.java b/src/test/java/org/apache/commons/csv/CSVParserTest.java
index c0f497f7..fd9de361 100644
--- a/src/test/java/org/apache/commons/csv/CSVParserTest.java
+++ b/src/test/java/org/apache/commons/csv/CSVParserTest.java
@@ -1564,19 +1564,25 @@ public class CSVParserTest {
 
     @Test
     public void testParsingPrintedEmptyFirstColumn() throws Exception {
+        String[][] lines = new String[][] {
+                {"a", "b"},
+                {"", "x"}
+        };
         Exception firstException = null;
         for (CSVFormat.Predefined format : CSVFormat.Predefined.values()) {
             try {
                 StringWriter buf = new StringWriter();
                 try (CSVPrinter printer = new CSVPrinter(buf, format.getFormat())) {
-                    printer.printRecord("a", "b"); // header
-                    printer.printRecord("", "x");  // empty first column
-                }
-                try (CSVParser csvRecords = new CSVParser(new StringReader(buf.toString()), format.getFormat().builder().setHeader().build())) {
-                    for (CSVRecord csvRecord : csvRecords) {
-                        assertNotNull(csvRecord);
+                    for (String[] line : lines) {
+                        printer.printRecord((Object[]) line);
                     }
                 }
+                try (CSVParser csvRecords = new CSVParser(new StringReader(buf.toString()), format.getFormat())) {
+                    for (String[] line : lines) {
+                        assertArrayEquals(line, csvRecords.nextRecord().values());
+                    }
+                    assertNull(csvRecords.nextRecord());
+                }
             } catch (Exception | Error e) {
                 Exception detailedException = new RuntimeException("format: " + format, e);
                 if (firstException == null) {