From 4e2c4f24c1a63355749bc515218464218b8c8e23 Mon Sep 17 00:00:00 2001
From: Chris Masone <cmasone@atticlabs.io>
Date: Wed, 10 Feb 2016 11:27:31 -0800
Subject: [PATCH] Change csv.Write() signature to broaden uses The old
 csv.Write() signature required passing in a Dataset whose Head() contained a
 List of structs. Not all data that we want to export as CSV will be the Head
 of a Dataset, so this patch makes the function a bit more flexible.

---
 clients/csv/common.go            |  2 +-
 clients/csv/exporter/.gitignore  |  1 +
 clients/csv/exporter/exporter.go |  3 ++-
 clients/csv/write.go             | 46 +++++++++++++++-----------------
 4 files changed, 26 insertions(+), 26 deletions(-)
 create mode 100644 clients/csv/exporter/.gitignore

diff --git a/clients/csv/common.go b/clients/csv/common.go
index 84e36b5bea..861494061c 100644
--- a/clients/csv/common.go
+++ b/clients/csv/common.go
@@ -5,7 +5,7 @@ import (
 	"unicode/utf8"
 )
 
-// Returns the rune contained in delimiter or an error.
+// StringToRune returns the rune contained in delimiter or an error.
 func StringToRune(delimiter string) (rune, error) {
 	dlimLen := len(delimiter)
 	if dlimLen == 0 {
diff --git a/clients/csv/exporter/.gitignore b/clients/csv/exporter/.gitignore
new file mode 100644
index 0000000000..9cfaec5af1
--- /dev/null
+++ b/clients/csv/exporter/.gitignore
@@ -0,0 +1 @@
+exporter
diff --git a/clients/csv/exporter/exporter.go b/clients/csv/exporter/exporter.go
index fd12323838..666968ef4c 100644
--- a/clients/csv/exporter/exporter.go
+++ b/clients/csv/exporter/exporter.go
@@ -44,7 +44,8 @@ func main() {
 	}
 
 	err = d.Try(func() {
-		csv.Write(ds, comma, *p, os.Stdout)
+		nomsList, structDesc := csv.ValueToListAndElemDesc(ds.Head().Value(), ds.Store())
+		csv.Write(nomsList, structDesc, comma, *p, os.Stdout)
 	})
 	if err != nil {
 		fmt.Println("Failed to export dataset as CSV:")
diff --git a/clients/csv/write.go b/clients/csv/write.go
index cc1c921b18..95b380488c 100644
--- a/clients/csv/write.go
+++ b/clients/csv/write.go
@@ -5,22 +5,13 @@ import (
 	"fmt"
 	"io"
 
+	"github.com/attic-labs/noms/chunks"
 	"github.com/attic-labs/noms/d"
-	"github.com/attic-labs/noms/dataset"
 	"github.com/attic-labs/noms/types"
 )
 
-func getFieldNamesFromStruct(structDesc types.StructDesc) (fieldNames []string) {
-	for _, f := range structDesc.Fields {
-		d.Exp.Equal(true, types.IsPrimitiveKind(f.T.Desc.Kind()),
-			"Non-primitive CSV export not supported:", f.T.Desc.Describe())
-		fieldNames = append(fieldNames, f.Name)
-	}
-	return
-}
-
-func datasetToHeaderAndList(ds *dataset.Dataset) (fieldNames []string, nomsList types.List) {
-	v := ds.Head().Value()
+// ValueToListAndElemDesc ensures that v is a types.List of structs, pulls the types.StructDesc that describes the elements of v out of cs, and returns the List and related StructDesc.
+func ValueToListAndElemDesc(v types.Value, cs chunks.ChunkSource) (types.List, types.StructDesc) {
 	d.Exp.Equal(types.ListKind, v.Type().Desc.Kind(),
 		"Dataset must be List<>, found: %s", v.Type().Desc.Describe())
 
@@ -28,29 +19,27 @@ func datasetToHeaderAndList(ds *dataset.Dataset) (fieldNames []string, nomsList
 	d.Exp.Equal(types.UnresolvedKind, u.Desc.Kind(),
 		"List<> must be UnresolvedKind, found: %s", u.Desc.Describe())
 
-	pkg := types.ReadPackage(u.PackageRef(), ds.Store())
+	pkg := types.ReadPackage(u.PackageRef(), cs)
 	d.Exp.Equal(types.PackageKind, pkg.Type().Desc.Kind(),
 		"Failed to read package: %s", pkg.Type().Desc.Describe())
 
-	structDesc := pkg.Types()[u.Ordinal()].Desc
-	d.Exp.Equal(types.StructKind, structDesc.Kind(),
-		"Did not find Struct: %s", structDesc.Describe())
-
-	fieldNames = getFieldNamesFromStruct(structDesc.(types.StructDesc))
-	nomsList = v.(types.List)
-	return
+	desc := pkg.Types()[u.Ordinal()].Desc
+	d.Exp.Equal(types.StructKind, desc.Kind(), "Did not find Struct: %s", desc.Describe())
+	return v.(types.List), desc.(types.StructDesc)
 }
 
-func Write(ds *dataset.Dataset, comma rune, concurrency int, output io.Writer) {
-	fieldNames, nomsList := datasetToHeaderAndList(ds)
+// Write takes a types.List l of structs (described by sd) and writes it to output as comma-delineated values.
+func Write(l types.List, sd types.StructDesc, comma rune, concurrency int, output io.Writer) {
+	d.Exp.Equal(types.StructKind, sd.Kind(), "Did not find Struct: %s", sd.Describe())
+	fieldNames := getFieldNamesFromStruct(sd)
 
 	csvWriter := csv.NewWriter(output)
 	csvWriter.Comma = comma
 
-	records := make([][]string, nomsList.Len()+1)
+	records := make([][]string, l.Len()+1)
 	records[0] = fieldNames // Write header
 
-	nomsList.IterAllP(concurrency, func(v types.Value, index uint64) {
+	l.IterAllP(concurrency, func(v types.Value, index uint64) {
 		for _, f := range fieldNames {
 			records[index+1] = append(
 				records[index+1],
@@ -63,3 +52,12 @@ func Write(ds *dataset.Dataset, comma rune, concurrency int, output io.Writer) {
 	err := csvWriter.Error()
 	d.Exp.Equal(nil, err, "error flushing csv:", err)
 }
+
+func getFieldNamesFromStruct(structDesc types.StructDesc) (fieldNames []string) {
+	for _, f := range structDesc.Fields {
+		d.Exp.Equal(true, types.IsPrimitiveKind(f.T.Desc.Kind()),
+			"Non-primitive CSV export not supported:", f.T.Desc.Describe())
+		fieldNames = append(fieldNames, f.Name)
+	}
+	return
+}