Add none formatting option

Author: ianlopshire

README.md

@@ -12,7 +12,7 @@ The struct tag schema schema used by fixedwidth is: `fixed:"{startPos},{endPos},
 
 The `startPos` and `endPos` arguments control the position within a line. `startPos` and `endPos` must both be positive integers greater than 0. Positions start at 1. The interval is inclusive. 
 
-The `alignment` argument controls the alignment of the value within it's interval. The valid options are `default`<sup id="a2">[2](#f2)</sup>, `right`, and `left`. The `alignment` is optional and can be omitted.
+The `alignment` argument controls the alignment of the value within it's interval. The valid options are `default`<sup id="a2">[2](#f2)</sup>, `right`, `left`, and `none`. The `alignment` is optional and can be omitted.
 
 The `padChar` argument controls the character that will be used to pad any empty characters in the interval after writing the value. The default padding character is a space. The `padChar` is optional and can be omitted.
 
@@ -120,6 +120,7 @@ encoder.SetUseCodepointIndices(true)
 | `default` | Field is left aligned | The padding character is trimmed from both right and left of value |
 | `left` | Field is left aligned | The padding character is trimmed from right of value |
 | `right` | Field is right aligned | The padding character is trimmed from left of value |
+| `none` | Field is left aligned | The padding character is not trimmed from value. Useful for nested structs. |
 
 ## Notes
 1. <span id="f1">`{}` indicates an argument. `[]` indicates and optional segment [^](#a1)</span>

decode.go

@@ -207,6 +207,8 @@ func rawValueFromLine(value rawValue, startPos, endPos int, format format) rawVa
 		trimFunc = func(r rawValue) rawValue {
 			return r.trimLeft(string(format.padChar))
 		}
+	case alignmentNone:
+		trimFunc = func(r rawValue) rawValue { return r }
 	default:
 		trimFunc = func(r rawValue) rawValue {
 			return r.trim(string(format.padChar))

decode_test.go

@@ -386,17 +386,17 @@ func TestDecodeSetUseCodepointIndices(t *testing.T) {
 
 }
 
-func TestDecodeSetUseCodepointIndices_Nested(t *testing.T) {
+func TestDecode_Nested(t *testing.T) {
 	type Nested struct {
 		First  string `fixed:"1,3"`
 		Second string `fixed:"4,6"`
 	}
 
 	type Test struct {
 		First  string `fixed:"1,3"`
-		Second Nested `fixed:"4,9"`
+		Second Nested `fixed:"4,9,none"`
 		Third  string `fixed:"10,12"`
-		Fourth Nested `fixed:"13,18"`
+		Fourth Nested `fixed:"13,18,none"`
 		Fifth  string `fixed:"19,21"`
 	}
 
@@ -416,6 +416,17 @@ func TestDecodeSetUseCodepointIndices_Nested(t *testing.T) {
 				Fifth:  "012",
 			},
 		},
+		{
+			name: "All ASCII characters with padding",
+			raw:  []byte(" 2  B  5  E  8  H  1 \n"),
+			expected: Test{
+				First:  "2",
+				Second: Nested{First: "B", Second: "5"},
+				Third:  "E",
+				Fourth: Nested{First: "8", Second: "H"},
+				Fifth:  "1",
+			},
+		},
 		{
 			name: "Multi-byte characters",
 			raw:  []byte("123x☃x456x☃x789x☃x012\n"),
@@ -427,63 +438,15 @@ func TestDecodeSetUseCodepointIndices_Nested(t *testing.T) {
 				Fifth:  "012",
 			},
 		},
-	} {
-		t.Run(tt.name, func(t *testing.T) {
-			d := NewDecoder(bytes.NewReader(tt.raw))
-			d.SetUseCodepointIndices(true)
-			var s Test
-			err := d.Decode(&s)
-			if err != nil {
-				t.Errorf("Unexpected err: %v", err)
-			}
-			if !reflect.DeepEqual(tt.expected, s) {
-				t.Errorf("Decode(%v) want %v, have %v", tt.raw, tt.expected, s)
-			}
-		})
-	}
-}
-
-func TestDecodeSetUseCodepointIndices_PaddingTrimmed(t *testing.T) {
-	type Nested struct {
-		First  int64  `fixed:"1,2,right,0"`
-		Second string `fixed:"3,4"`
-		Third  string `fixed:"5,6"`
-		Fourth string `fixed:"7,8"`
-	}
-	type Test struct {
-		First  Nested `fixed:"1,8"`
-		Second string `fixed:"9,10"`
-	}
-
-	for _, tt := range []struct {
-		name     string
-		raw      []byte
-		expected Test
-	}{
-		{
-			name: "All ASCII characters",
-			raw:  []byte("00      11"),
-			expected: Test{
-				First: Nested{
-					First:  0,
-					Second: "",
-					Third:  "",
-					Fourth: "",
-				},
-				Second: "11",
-			},
-		},
 		{
-			name: "Multi-byte characters",
-			raw:  []byte("00      ☃☃"),
+			name: "Multi-byte characters with padding",
+			raw:  []byte(" ☃  Ñ  ☃  Ñ  ☃  Ñ  ☃ \n"),
 			expected: Test{
-				First: Nested{
-					First:  0,
-					Second: "",
-					Third:  "",
-					Fourth: "",
-				},
-				Second: "☃☃",
+				First:  "☃",
+				Second: Nested{First: "Ñ", Second: "☃"},
+				Third:  "Ñ",
+				Fourth: Nested{First: "☃", Second: "Ñ"},
+				Fifth:  "☃",
 			},
 		},
 	} {

format.go

@@ -2,6 +2,7 @@ package fixedwidth
 
 const (
 	defaultAlignment alignment = "default"
+	alignmentNone    alignment = "none"
 	right            alignment = "right"
 	left             alignment = "left"
 )
@@ -24,7 +25,7 @@ type alignment string
 
 func (a alignment) Valid() bool {
 	switch a {
-	case defaultAlignment, right, left:
+	case defaultAlignment, right, left, alignmentNone:
 		return true
 	default:
 		return false