From feee60ed9179504a3b7ed94ee19e4a8e4ac025e2 Mon Sep 17 00:00:00 2001
From: Nicolas Steenlant <nicolas.steenlant@ugent.be>
Date: Mon, 4 Dec 2017 13:38:22 +0100
Subject: [PATCH] print csv header even if record stream is empty

---
 lib/Catmandu/Exporter/CSV.pm | 20 +++++++++++++++-----
 t/Catmandu-Exporter-CSV.t    | 16 ++++++++++++++++
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/lib/Catmandu/Exporter/CSV.pm b/lib/Catmandu/Exporter/CSV.pm
index 37bf5c9f3..e76cd327d 100644
--- a/lib/Catmandu/Exporter/CSV.pm
+++ b/lib/Catmandu/Exporter/CSV.pm
@@ -42,14 +42,24 @@ sub add {
             $val;
         } @$fields
     ];
-    my $fh = $self->fh;
 
-    # header
+    $self->_print_header;
+    $self->csv->print($self->fh, $row);
+}
+
+sub commit {
+    my ($self) = @_;
+
+    # ensure header gets printed even if there are no records
+    $self->_print_header;
+}
+
+sub _print_header {
+    my ($self) = @_;
     if (!$self->count && $self->header) {
-        $self->csv->print($fh, $self->columns || $fields);
+        my $row = $self->columns || $self->fields;
+        $self->csv->print($self->fh, $row) if $row && @$row;
     }
-
-    $self->csv->print($fh, $row);
 }
 
 1;
diff --git a/t/Catmandu-Exporter-CSV.t b/t/Catmandu-Exporter-CSV.t
index 353dc96e8..a953b2d63 100644
--- a/t/Catmandu-Exporter-CSV.t
+++ b/t/Catmandu-Exporter-CSV.t
@@ -75,4 +75,20 @@ $exporter->add_many($fixer->fix($importer));
 $csv = "fob\ntest\n";
 is $out, $csv, "custom column names as HASH with reject fix";
 
+# empty exports
+$out = "";
+$exporter = $pkg->new(file => \$out, header => 0);
+$exporter->commit;
+is $out, "";
+$out = "";
+$exporter = $pkg->new(file => \$out);
+$exporter->commit;
+is $out, "";
+$out = "";
+$exporter = $pkg->new(file => \$out, fields => 'a,b');
+$exporter->commit;
+$csv = <<EOF;
+a,b
+EOF
+
 done_testing;