Improved the behaviour of parseFile wrt. when sections are defined.

* Only create the default section if it is not empty.
* Always create user defined sections, even when empty.
* Added a test for this: TestDefinedSectionBehaviour

README.md

@@ -28,20 +28,18 @@ if !ok {
 Iterate through values in a section:
 
 ```go
-for key, value := range file.Section("mysection") {
+for key, value := range file["mysection"] {
   fmt.Printf("%s => %s\n", key, value)
 }
 ```
 
 Iterate through sections in a file:
 
 ```go
-for sectionName, section := range file {
-  fmt.Printf("Section name: %s", sectionName)
+for name, section := range file {
+  fmt.Printf("Section name: %s\n", name)
 }
 ```
-Note that the current implementation always includes the empty section
-when iterating.
 
 File Format
 -----------

ini.go

@@ -68,7 +68,7 @@ func (f File) LoadFile(file string) (err error) {
 }
 
 func parseFile(in *bufio.Reader, file File) (err error) {
-	section := file.Section("")
+	section := ""
 	lineNum := 0
 	for done := false; !done; {
 		var line string
@@ -93,10 +93,12 @@ func parseFile(in *bufio.Reader, file File) (err error) {
 		if groups := assignRegex.FindStringSubmatch(line); groups != nil {
 			key, val := groups[1], groups[2]
 			key, val = strings.TrimSpace(key), strings.TrimSpace(val)
-			section[key] = val
+			file.Section(section)[key] = val
 		} else if groups := sectionRegex.FindStringSubmatch(line); groups != nil {
 			name := strings.TrimSpace(groups[1])
-			section = file.Section(name)
+			section = name
+			// Create the section if it does not exist
+			file.Section(section)
 		} else {
 			return ErrSyntax{lineNum, line}
 		}

ini_test.go

@@ -1,6 +1,7 @@
 package ini
 
 import (
+	"reflect"
 	"strings"
 	"testing"
 )
@@ -61,3 +62,28 @@ func TestSyntaxError(t *testing.T) {
 		t.Fatal("incorrect source")
 	}
 }
+
+func TestDefinedSectionBehaviour(t *testing.T) {
+	check := func(src string, expect File) {
+		file, err := Load(strings.NewReader(src))
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !reflect.DeepEqual(file, expect) {
+			t.Errorf("expected %v, got %v", expect, file)
+		}
+	}
+	// No sections for an empty file
+	check("", File{})
+	// Default section only if there are actually values for it
+	check("foo=bar", File{"": {"foo": "bar"}})
+	// User-defined sections should always be present, even if empty
+	check("[a]\n[b]\nfoo=bar", File{
+		"a": {},
+		"b": {"foo": "bar"},
+	})
+	check("foo=bar\n[a]\nthis=that", File{
+		"":  {"foo": "bar"},
+		"a": {"this": "that"},
+	})
+}