add location to parse errors

Fixes #11

errors.go

@@ -1,8 +1,6 @@
 package gcfg
 
-import (
-	"gopkg.in/warnings.v0"
-)
+import warnings "gopkg.in/warnings.v0"
 
 // FatalOnly filters the results of a Read*Into invocation and returns only
 // fatal errors. That is, errors (warnings) indicating data for unknown
@@ -21,21 +19,39 @@ func isFatal(err error) bool {
 	return !ok
 }
 
-type extraData struct {
+type loc struct {
 	section    string
 	subsection *string
 	variable   *string
 }
 
-func (e extraData) Error() string {
-	s := "can't store data at section \"" + e.section + "\""
-	if e.subsection != nil {
-		s += ", subsection \"" + *e.subsection + "\""
+type extraData struct {
+	loc
+}
+
+type locErr struct {
+	msg string
+	loc
+}
+
+func (l loc) String() string {
+	s := "section \"" + l.section + "\""
+	if l.subsection != nil {
+		s += ", subsection \"" + *l.subsection + "\""
 	}
-	if e.variable != nil {
-		s += ", variable \"" + *e.variable + "\""
+	if l.variable != nil {
+		s += ", variable \"" + *l.variable + "\""
 	}
 	return s
 }
 
+func (e extraData) Error() string {
+	return "can't store data at " + e.loc.String()
+}
+
+func (e locErr) Error() string {
+	return e.msg + " at " + e.loc.String()
+}
+
 var _ error = extraData{}
+var _ error = locErr{}

issues_test.go

@@ -61,3 +61,34 @@ func TestGoogleCodeIssue2(t *testing.T) {
 		testRead(t, id, tt)
 	}
 }
+
+type ConfigIssue11 struct {
+	Sect struct {
+		Var bool
+	}
+}
+
+var testsIssue11 = []struct {
+	cfg string
+	loc string
+}{
+	{"[Sect]\nVar=X", "Sect"},
+	{"[Sect]\nVar=X", "Var"},
+}
+
+// Value parse error should include location
+func TestIssue11(t *testing.T) {
+	for i, tt := range testsIssue11 {
+		var c ConfigIssue11
+		err := ReadStringInto(&c, tt.cfg)
+		switch {
+		case err == nil:
+			t.Errorf("%d fail: got ok; wanted error", i)
+		case !strings.Contains(err.Error(), tt.loc):
+			t.Errorf("%d fail: error message doesn't contain location %q: %v",
+				i, tt.loc, err)
+		default:
+			t.Logf("%d pass: %v", i, err)
+		}
+	}
+}

set.go

@@ -222,15 +222,17 @@ func set(c *warnings.Collector, cfg interface{}, sect, sub, name string,
 	}
 	vCfg := vPCfg.Elem()
 	vSect, _ := fieldFold(vCfg, sect)
+	l := loc{section: sect}
 	if !vSect.IsValid() {
-		err := extraData{section: sect}
+		err := extraData{loc: l}
 		return c.Collect(err)
 	}
 	isSubsect := vSect.Kind() == reflect.Map
 	if subsectPass != isSubsect {
 		return nil
 	}
 	if isSubsect {
+		l.subsection = &sub
 		vst := vSect.Type()
 		if vst.Key().Kind() != reflect.String ||
 			vst.Elem().Kind() != reflect.Ptr ||
@@ -256,23 +258,17 @@ func set(c *warnings.Collector, cfg interface{}, sect, sub, name string,
 		panic(fmt.Errorf("field for section must be a map or a struct: "+
 			"section %q", sect))
 	} else if sub != "" {
-		err := extraData{section: sect, subsection: &sub}
-		return c.Collect(err)
+		return c.Collect(extraData{loc: l})
 	}
 	// Empty name is a special value, meaning that only the
 	// section/subsection object is to be created, with no values set.
 	if name == "" {
 		return nil
 	}
 	vVar, t := fieldFold(vSect, name)
+	l.variable = &name
 	if !vVar.IsValid() {
-		var err error
-		if isSubsect {
-			err = extraData{section: sect, subsection: &sub, variable: &name}
-		} else {
-			err = extraData{section: sect, variable: &name}
-		}
-		return c.Collect(err)
+		return c.Collect(extraData{loc: l})
 	}
 	// vVal is either single-valued var, or newly allocated value within multi-valued var
 	var vVal reflect.Value
@@ -315,12 +311,12 @@ func set(c *warnings.Collector, cfg interface{}, sect, sub, name string,
 			break
 		}
 		if err != errUnsupportedType {
-			return err
+			return locErr{msg: err.Error(), loc: l}
 		}
 	}
 	if !ok {
 		// in case all setters returned errUnsupportedType
-		return err
+		return locErr{msg: err.Error(), loc: l}
 	}
 	if isNew { // set reference if it was dereferenced and newly allocated
 		vVal.Set(vAddr)