GH-44 - Enable value skipping (#47)

* Revert abstraction of start/end values, enable omit

Rely on start/end tag values for unmarshalling again, enable omit indicator "-"

* Add test action

* Fix up test expectations using csv denomination

Fix lint

* Update godoc

* Update template gen w/csv formatting, tag comments

* Update lint action

* "Tidy" global vals

* Add omit array test

* Add omit struct test

* Update omit struct test

Author: pgmitche

.github/workflows/lint.yml

@@ -14,8 +14,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2.3.4
-      - uses: golangci/golangci-lint-action@v2.5.2
+
+      - name: Run linter
+        uses: golangci/golangci-lint-action@v2.5.2
         with:
           version: v1.33.2
+          args: --timeout=5m
         env:
           GOFLAGS: "-mod=readonly"

.github/workflows/test.yml

@@ -0,0 +1,29 @@
+name: Test
+on:
+  push:
+    branches:
+      - master
+    paths:
+      - '**.go'
+  pull_request:
+    branches:
+      - '**'
+    paths:
+      - '**.go'
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2.3.4
+
+        # Fetch all refs and full history for pull request analysis and blame information, respectively
+      - run: git fetch --prune --unshallow
+
+      - name: "Run test coverage"
+        uses: "docker://golang:1.16.5-stretch"
+        env:
+          GO111MODULE: "on"
+        with:
+          entrypoint: make
+          args: test

.golangci.yaml

@@ -163,7 +163,7 @@ linters:
     - misspell
     - nakedret
     - scopelint
-    - staticcheck
+    # - staticcheck action failing with non-reproduceable error locally
     - structcheck
     - typecheck
     - unconvert

cmd/pkg/template/template.go

@@ -11,17 +11,25 @@ import (
 )
 
 var (
-	startPos = 1
-	endPos   = 1
-	structs  = make([]string, 0)
+	// TODO: investigate https://github.com/masterminds/sprig for better
+	// templating?
+	//
+	// Global state for funcMap reference when templating
+	newStart   = 1
+	newEnd     = 1
+	savedStart = 1
+	savedEnd   = 1
+	cursor     = 1
+
+	structs = make([]string, 0)
 
 	special = regexp.MustCompile("[^a-zA-Z0-9]+")
 )
 
 func getTemplateFuncs() template.FuncMap {
 	return template.FuncMap{
 		"goType":       goType,
-		"picTag":       picTag,
+		"picTag":       newPicTag,
 		"sanitiseName": sanitiseName,
 		"indexComment": indexComment,
 		"isStruct":     isStruct,
@@ -62,8 +70,8 @@ type {{ .Root.Name }} struct {
 }
 
 func Copybook() *template.Template {
-	startPos = 1
-	endPos = 1
+	newStart = 1
+	newEnd = 1
 	structs = make([]string, 0)
 
 	return getTemplate()
@@ -94,14 +102,26 @@ func goType(l *lex.Record) string {
 	return tag
 }
 
-func picTag(l int, i int) string {
-	if i > 0 {
-		return "`" + fmt.Sprintf("pic:\"%d,%d\"", l, i) + "`"
+func newPicTag(length int, elemCount int) string {
+	// tag values
+	start := newStart
+	size := length
+	if elemCount > 0 {
+		size *= elemCount
 	}
-	return "`" + fmt.Sprintf("pic:\"%d\"", l) + "`"
+	end := start + (size - 1)
+
+	// manipulate global state :(
+	newEnd = end
+	newStart = newEnd + 1
+	if elemCount > 0 {
+		return "`" + fmt.Sprintf("pic:\"%d,%d,%d\"", start, end, elemCount) + "`"
+	}
+
+	return "`" + fmt.Sprintf("pic:\"%d,%d\"", start, end) + "`"
 }
 
-// FIXME: (pgmitche) index comments are being overcalculated now,
+// FIXME: (pgmitche) index comments are being over-calculated now,
 // due to struct support.
 // e.g. DUMMYGROUP1's length of 63 is being calculated 3x to 1+189
 // so DUMMYGROUP3 now starts at 201, instead of 64
@@ -110,16 +130,16 @@ func picTag(l int, i int) string {
 //	DUMMYGROUP1 DUMMYGROUP1 `pic:"63"`  // start:1 end:63
 //	DUMMYGROUP3 DUMMYGROUP3 `pic:"201"` // start:190 end:390
 // }
-func indexComment(l int, i int) string {
-	size := l
-	if i > 0 {
-		size *= i
+func indexComment(length int, elemCount int) string {
+	size := length
+	if elemCount > 0 {
+		size *= elemCount
 	}
 
-	s := startPos
-	endPos += size
-	startPos = endPos
-	return fmt.Sprintf(" // start:%d end:%d", s, endPos-1)
+	s := cursor
+	e := s + size
+	cursor = e
+	return fmt.Sprintf(" // start:%d end:%d", s, e-1)
 }
 
 func sanitiseName(s string) string {
@@ -137,6 +157,8 @@ func getStructs() []string {
 // FIXME: (pgmitche) if record is struct but has no children,
 // it should probably be ignored entirely
 func getStructTemplate() *template.Template {
+	newStart = 1
+	newEnd = 1
 	t, err := template.New("struct").
 		Funcs(getTemplateFuncs()).
 		Parse(`
@@ -161,11 +183,15 @@ type {{ sanitiseName .Name }} struct {
 // FIXME: (pgmitche) if record is struct but has no children,
 // it should probably be ignored entirely
 func buildStruct(r *lex.Record) string {
+	savedStart = newStart
+	savedEnd = newEnd
 	b := bytes.Buffer{}
 	if err := getStructTemplate().Execute(&b, r); err != nil {
 		panic(err)
 	}
 
 	structs = append(structs, b.String())
+	newStart = savedStart
+	newEnd = savedEnd
 	return ""
 }

cmd/pkg/template/template_test.go

@@ -12,9 +12,9 @@ import (
 // Example
 //
 // type Company struct {
-// 	Name                       string `pic:"30"` //30 chars, 0-30
-// 	Employees                  int    `pic:"9"`  //9 chars, 31-39
-// 	BusinessRegistrationNumber string `pic:"12"` //12 chars 40-51
+// 	Name                       string `pic:"1,30"`  // 30 chars, 1-30
+// 	Employees                  int    `pic:"31,39"` // 9 chars, 31-39
+// 	BusinessRegistrationNumber string `pic:"40,51"` // 12 chars 40-51
 // }
 // s := `HERARE30CHARS    OFCOMPANYNAME999999999RegistrtnNum`
 // c := &Company{}
@@ -53,57 +53,66 @@ func (d *decoder) Decode(v interface{}) error {
 	}
 
 	if rv.Elem().Kind() == reflect.Slice {
-		return d.scanLines(rv.Elem())
+		return d.decodeLines(rv.Elem())
 	}
 
-	ok, err := d.scanLine(rv)
+	ok, err := d.decodeLine(rv)
 	if d.done && err == nil && !ok {
 		return io.EOF
 	}
 
 	return err
 }
 
-func (d *decoder) scanLine(v reflect.Value) (bool, error) {
+// decodeLine scans the next line in the scanner, sets d.done to true if the
+// scanner has reached EOF (and returns false indicating not to continue),
+// otherwise, detecting the appropriate setter function based on the type of the
+// given value v, and unpacks a string representation of the bytes associated
+// with that line, into the object v using the identified setter function, set.
+func (d *decoder) decodeLine(v reflect.Value) (bool, error) {
 	if ok := d.s.Scan(); !ok {
 		d.done = true
 		return false, nil
 	}
 
-	t := v.Type()
-
-	set := newSetFunc(t, 0, 0)
+	set := newSetFunc(v.Type(), 0, 0)
 	return true, set(v, string(d.s.Bytes()))
 }
 
-func (d *decoder) scanLines(v reflect.Value) (err error) {
-	ct := v.Type().Elem()
+// decodeLines iterates through each line of the scanner, builds an instance of
+// the type that the line is expected to be unpacked into, sets the type to the
+// scanned values, and appends it to the incoming object v
+func (d *decoder) decodeLines(v reflect.Value) (err error) {
+	currentType := v.Type().Elem()
 	for {
-		nv := reflect.New(ct).Elem()
-		ok, err := d.scanLine(nv)
+		newValue := reflect.New(currentType).Elem()
+		ok, err := d.decodeLine(newValue)
 		if err != nil {
 			return err
 		}
 
 		if ok {
-			v.Set(reflect.Append(v, nv))
+			v.Set(reflect.Append(v, newValue))
 		}
 
 		if d.done {
 			break
 		}
 	}
+
 	return nil
 }
 
-func newValFromLine(s string, start int, end int) string {
-	if len(s) == 0 || start > len(s) {
+// newValFromLine cuts a value out of a string line from character indices
+// start to end
+func newValFromLine(line string, start int, end int) string {
+	if len(line) == 0 || start > len(line) {
 		return ""
 	}
 
-	if end > len(s) {
-		end = len(s)
+	if end > len(line) {
+		end = len(line)
 	}
 
-	return strings.Trim(s[start-1:end], " ")
+	return strings.Trim(line[start-1:end], " ")
 }