writeOptions.newColumns

If `writeOptions.columns` is not defined and `writeOptions.newColumns` is defined, any new keys
added to the object returned by `transform()` will be added as an output column.

See #31

lib/csv.js

@@ -54,6 +54,7 @@ module.exports = function(){
             flags: 'w',
             encoding: 'utf8',
             bufferSize: null,
+            newColumns: false,
             end: true // Call `end()` on close
         };
         // A boolean that is true by default, but turns false after an 'error' occurred, 
@@ -334,17 +335,24 @@ module.exports = function(){
             state.line = line;
             line = null;
         }
-        if(state.count === 0 && csv.writeOptions.header === true){
-            write(csv.writeOptions.columns || csv.readOptions.columns);
-        }
         var line;
         if(csv.transformer){
             transforming = true;
             line = csv.transformer(state.line, state.count);
+
+            if (csv.writeOptions.newColumns && !csv.writeOptions.columns && typeof line === 'object' && !Array.isArray(line)) {
+                Object.keys(line)
+                .filter(function(column) { return csv.readOptions.columns.indexOf(column) === -1; })
+                .forEach(function(column) { csv.readOptions.columns.push(column); });
+            }
+
             transforming = false;
         }else{
             line = state.line;
         }
+        if(state.count === 0 && csv.writeOptions.header === true){
+            write(csv.writeOptions.columns || csv.readOptions.columns);
+        }
         write(line);
         state.count++;
         state.line = [];

package.json

@@ -1,6 +1,6 @@
 {
   "name": "csv",
-  "version": "0.0.13",
+  "version": "0.0.14",
   "description": "CSV parser with simple api, full of options and tested against large datasets.",
   "author": "David Worms <david@adaltas.com>",
   "contributors": [

readme.md

@@ -156,6 +156,11 @@ Options are:
 -   *end*    
     Prevent calling `end` on the destination, so that destination is no longer writable, similar to passing `{end: false}` option in `stream.pipe()`.
 
+-   *newColumns*
+    If the `columns` option is not specified (which means columns will be taken from the reader
+    options, will automatically append new columns if they are added during `transform()`.
+
+
 Transforming data
 -----------------
 

samples/new-columns.in

@@ -0,0 +1,3 @@
+id,lastname,firstname
+82,Preisner,Zbigniew
+94,Gainsbourg,Serge

samples/new-columns.js

@@ -0,0 +1,22 @@
+
+// CSV sample - Copyright David Worms <open@adaltas.com> (BSD Licensed)
+
+    // node samples/column.js
+    var csv = require('..');
+
+    csv()
+    .fromPath(__dirname+'/columns.in',{
+        columns: true
+    })
+    .toStream(process.stdout, {
+        newColumns: true,
+        end: false
+    })
+    .transform(function(data){
+        data.name = data.firstname + ' ' + data.lastname
+        return data;
+    });
+
+    // Will print sth like:
+    // 82,Preisner,Zbigniew,Zbigniew Preisner
+    // 94,Gainsbourg,Serge,Serge Gainsbourg

test/columns.coffee

@@ -90,7 +90,21 @@ describe 'columns', ->
                 result.should.eql expect
                 fs.unlink "#{__dirname}/columns/out_named.tmp"
                 next()
-
+        it 'should emit new columns in output', (next) ->
+            csv()
+            .fromPath("#{__dirname}/columns/out_new.in", columns: true)
+            .toPath("#{__dirname}/columns/out_new.tmp", newColumns: true, header: true)
+            .transform (data) ->
+                data.should.be.an.a 'object'
+                data.FIELD_7 = 'new_field'
+                data
+            .on 'end', (count) ->
+                count.should.eql 2
+                expect = fs.readFileSync("#{__dirname}/columns/out_new.out").toString()
+                result = fs.readFileSync("#{__dirname}/columns/out_new.tmp").toString()
+                result.should.eql expect
+                fs.unlink "#{__dirname}/columns/out_new.tmp"
+                next()
 
 
 

test/columns/out_new.in

@@ -0,0 +1,3 @@
+FIELD_1,FIELD_2,FIELD_3,FIELD_4,FIELD_5,FIELD_6
+20322051544,1979,8.8017226E7,ABC,45,2000-01-01
+28392898392,1974,8.8392926E7,DEF,23,2050-11-27

test/columns/out_new.out

@@ -0,0 +1,3 @@
+FIELD_1,FIELD_2,FIELD_3,FIELD_4,FIELD_5,FIELD_6,FIELD_7
+20322051544,1979,8.8017226E7,ABC,45,2000-01-01,new_field
+28392898392,1974,8.8392926E7,DEF,23,2050-11-27,new_field