Implemnt #56

release-notes/CREDITS

@@ -28,3 +28,10 @@ Wei Li (wli600@github)
 * Contributed fix for 54: Encounter ArrayIndexOutOfBoundsException in the corner case delimiter
   or end-of-line happened to be the leading character of a segment buffer
  (2.4.4)
+
+Luke Nezda (nezda@github)
+
+* Suggested #56: Support comments (either via `CsvSchema`, or using std
+  `JsonParser.Feature.ALLOW_YAML_COMMENTS.
+ (requested by nezda@github)
+ (2.5.0)

release-notes/VERSION

@@ -9,6 +9,8 @@ Project: jackson-dataformat-csv
 #50: Support `JsonGenerator.Feature.IGNORE_KNOWN` for CSV, to ignoring extra columns
 #53: Add a way to specify "null value" (String) for `CsvGenerator` to use when writing `null`s
  (part of `CsvSchema`; method `withNullValue()`)
+#56: Support comments (either via `CsvSchema`, or using std `JsonParser.Feature.ALLOW_YAML_COMMENTS.
+ (requested by nezda@github)
 #57: Support simple array types
 #61: Add a feature to always quote non-numeric values: `CsvGenerator.Feature.ALWAYS_QUOTE_STRINGS`
 

src/main/java/com/fasterxml/jackson/dataformat/csv/CsvParser.java

@@ -512,6 +512,8 @@ protected JsonToken _handleStartDoc() throws IOException
         if (_schema.skipsFirstDataRow()) {
             _reader.skipLine();
         }
+        // also, if comments enabled, may need to skip leading ones
+        _reader.skipLeadingComments();
 
         /* Only one real complication, actually; empy documents (zero bytes).
          * Those have no entries. Should be easy enough to detect like so:

src/main/java/com/fasterxml/jackson/dataformat/csv/impl/CsvDecoder.java

@@ -519,7 +519,7 @@ public boolean startNewLine() throws IOException
         }
 
         if (_allowComments && _inputBuffer[_inputPtr] == '#') {
-            int i = _skipCommentLine();
+            int i = _skipCommentLines();
             // end-of-input?
             if (i < 0) {
                 return false;
@@ -530,6 +530,37 @@ public boolean startNewLine() throws IOException
         return true;
     }
 
+    public void skipLeadingComments() throws IOException
+    {
+        if (_allowComments) {
+            if ((_inputPtr < _inputEnd) || loadMore()) {
+                if (_inputBuffer[_inputPtr] == '#') {
+                    _skipCommentLines();
+                    --_inputPtr;
+                }
+            }
+        }
+    }
+
+    protected int _skipCommentLines() throws IOException
+    {
+        while ((_inputPtr < _inputEnd) || loadMore()) {
+            char ch = _inputBuffer[_inputPtr++];
+            if (ch >= ' ' || (ch != '\r' && ch != '\n')) {
+                continue;
+            }
+            _pendingLF = ch;
+            _handleLF();
+
+            // Ok, skipped the end of the line. Check next one...
+            int i = _nextChar();
+            if (i != INT_HASH) {
+                return i;
+            }
+        }
+        return -1; // end of input
+    }
+
     public boolean skipLine() throws IOException
     {
         if (_pendingLF != 0) {
@@ -674,30 +705,6 @@ public JsonToken nextNumberOrString() throws IOException
         }
         return JsonToken.VALUE_STRING;
     }
-
-    protected int _skipCommentLine() throws IOException
-    {
-        while ((_inputPtr < _inputEnd) || loadMore()) {
-            char ch = _inputBuffer[_inputPtr++];
-            if (ch >= ' ' || (ch != '\r' && ch != '\n')) {
-                continue;
-            }
-            _pendingLF = ch;
-            _handleLF();
-
-            // Ok, skipped the end of the line. And parse next one...
-            int i;
-            if (_trimSpaces) {
-                i = _skipLeadingSpace();
-            } else {
-                i = _nextChar();
-            }
-            if (i != INT_HASH) {
-                return i;
-            }
-        }
-        return -1; // end of input
-    }
 
     /*
     /**********************************************************************