quick and dirty implementation of selective fs

generator.go

@@ -4,6 +4,7 @@ import (
 	"io/fs"
 	"math/rand"
 	"os/exec"
+	"strings"
 	"sync"
 	"time"
 
@@ -80,15 +81,93 @@ func (g *Generator) Box(box packd.Walker) error {
 	})
 }
 
+// ExceptFS walks through a given fs.FS and adds all files into Runner's
+// virtual disk, except files that starts with excludePrefix and ends with
+// excludeSuffix.
+// includePrefix and includeSuffix will be interpreted as AND condition
+// but an empty option will not be used. So if you give a prefix but
+// suffix as nil, it will only check if files starts with the given prefix.
+// It is usuful if you want to exclude entire subdirs.
+func (g *Generator) ExceptFS(fsys fs.FS, excludePrefix []string, excludeSuffix []string) error {
+	return g.SelectiveFS(fsys, nil, nil, excludePrefix, excludeSuffix)
+}
+
+// OnlyFS walks through a given fs.FS and adds only matching files into
+// Runner's virtual disk, matching files that starts with includePrefix
+// and ends with includeSuffix.
+// includePrefix and includeSuffix will be interpreted as AND condition
+// but an empty option will not be used. So if you give a prefix but
+// suffix as nil, it will only check if files starts with the given prefix.
+// It is usuful if you want to include specific subdirs only.
+func (g *Generator) OnlyFS(fsys fs.FS, includePrefix []string, includeSuffix []string) error {
+	return g.SelectiveFS(fsys, includePrefix, includeSuffix, nil, nil)
+}
+
 // FS walks through a fs.FS and adds Files for each entry.
 func (g *Generator) FS(fsys fs.FS) error {
+	return g.SelectiveFS(fsys, nil, nil, nil, nil)
+}
+
+// FS walks through a fs.FS and adds Files for each entry.
+func (g *Generator) SelectiveFS(fsys fs.FS, includePrefix, includeSuffix, excludePrefix, excludeSuffix []string) error {
 	return fs.WalkDir(fsys, ".", func(path string, d fs.DirEntry, err error) error {
 		if err != nil {
 			return err
 		}
 		if d.IsDir() {
 			return nil
 		}
+
+		isIncluded := false
+		isExcluded := false
+		if len(includePrefix) > 0 {
+			for _, fix := range includePrefix {
+				if strings.HasPrefix(path, fix) {
+					isIncluded = true
+					break
+				}
+			}
+		} else {
+			isIncluded = true
+		}
+		inSuffix := false
+		if len(includeSuffix) > 0 {
+			for _, fix := range includeSuffix {
+				if strings.HasSuffix(path, fix) {
+					inSuffix = true
+					break
+				}
+			}
+		} else {
+			inSuffix = true
+		}
+		isIncluded = isIncluded && inSuffix
+
+		for _, fix := range excludePrefix {
+			if strings.HasPrefix(path, fix) {
+				isExcluded = true
+				break
+			}
+		}
+		exSuffix := false
+		if len(excludeSuffix) == 0 {
+			exSuffix = isExcluded
+		}
+		for _, fix := range excludeSuffix {
+			if len(excludePrefix) == 0 {
+				isExcluded = true
+			}
+			exSuffix = isExcluded && strings.HasSuffix(path, fix)
+			if exSuffix {
+				break
+			}
+		}
+		isExcluded = exSuffix
+
+		if !isIncluded || isExcluded {
+			return nil
+		}
+
 		f, err := fsys.Open(path)
 		if err != nil {
 			return err