frontend/dockerfile/dockerignore: assorted cleanups

frontend/dockerfile/dockerignore/dockerignore.go

@@ -6,23 +6,31 @@ import (
 	"io"
 	"path/filepath"
 	"strings"
-
-	"github.com/pkg/errors"
 )
 
-// ReadAll reads a .dockerignore file and returns the list of file patterns
-// to ignore. Note this will trim whitespace from each line as well
-// as use GO's "clean" func to get the shortest/cleanest path for each.
+// ReadAll reads an ignore file from a reader and returns the list of file
+// patterns to ignore, applying the following rules:
+//
+//   - An UTF8 BOM header (if present) is stripped.
+//   - Lines starting with "#" are considered comments and are skipped.
+//
+// For remaining lines:
+//
+//   - Leading and trailing whitespace is removed from each ignore pattern.
+//   - It uses [filepath.Clean] to get the shortest/cleanest path for
+//     ignore patterns.
+//   - Leading forward-slashes ("/") are removed from ignore patterns,
+//     so "/some/path" and "some/path" are considered equivalent.
 func ReadAll(reader io.Reader) ([]string, error) {
 	if reader == nil {
 		return nil, nil
 	}
 
-	scanner := bufio.NewScanner(reader)
 	var excludes []string
 	currentLine := 0
-
 	utf8bom := []byte{0xEF, 0xBB, 0xBF}
+
+	scanner := bufio.NewScanner(reader)
 	for scanner.Scan() {
 		scannedBytes := scanner.Bytes()
 		// We trim UTF8 BOM
@@ -59,7 +67,7 @@ func ReadAll(reader io.Reader) ([]string, error) {
 		excludes = append(excludes, pattern)
 	}
 	if err := scanner.Err(); err != nil {
-		return nil, errors.Wrap(err, "error reading .dockerignore")
+		return nil, err
 	}
 	return excludes, nil
 }

frontend/dockerfile/dockerignore/dockerignore_test.go

@@ -1,61 +1,54 @@
 package dockerignore
 
 import (
-	"os"
-	"path/filepath"
+	"strings"
 	"testing"
 )
 
 func TestReadAll(t *testing.T) {
-	di, err := ReadAll(nil)
+	actual, err := ReadAll(nil)
 	if err != nil {
-		t.Fatalf("Expected not to have error, got %v", err)
+		t.Errorf("Expected no error, got %v", err)
 	}
-
-	if diLen := len(di); diLen != 0 {
-		t.Fatalf("Expected to have zero dockerignore entry, got %d", diLen)
+	if entries := len(actual); entries != 0 {
+		t.Fatalf("Expected to have zero entries, got %d", entries)
 	}
 
-	diName := filepath.Join(t.TempDir(), ".dockerignore")
-	content := "test1\n/test2\n/a/file/here\n\nlastfile\n# this is a comment\n! /inverted/abs/path\n!\n! \n"
-	err = os.WriteFile(diName, []byte(content), 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
+	const content = `test1
+/test2
+/a/file/here
 
-	diFd, err := os.Open(diName)
-	if err != nil {
-		t.Fatal(err)
+lastfile
+# this is a comment
+! /inverted/abs/path
+!
+! `
+
+	expected := []string{
+		"test1",
+		"test2",       // according to https://docs.docker.com/engine/reference/builder/#dockerignore-file, /foo/bar should be treated as foo/bar
+		"a/file/here", // according to https://docs.docker.com/engine/reference/builder/#dockerignore-file, /foo/bar should be treated as foo/bar
+		"lastfile",
+		"!inverted/abs/path",
+		"!",
+		"!",
 	}
-	defer diFd.Close()
 
-	di, err = ReadAll(diFd)
+	actual, err = ReadAll(strings.NewReader(content))
 	if err != nil {
-		t.Fatal(err)
+		t.Error(err)
 	}
 
-	if len(di) != 7 {
-		t.Fatalf("Expected 7 entries, got %v", len(di))
-	}
-	if di[0] != "test1" {
-		t.Fatal("First element is not test1")
-	}
-	if di[1] != "test2" { // according to https://docs.docker.com/engine/reference/builder/#dockerignore-file, /foo/bar should be treated as foo/bar
-		t.Fatal("Second element is not test2")
-	}
-	if di[2] != "a/file/here" { // according to https://docs.docker.com/engine/reference/builder/#dockerignore-file, /foo/bar should be treated as foo/bar
-		t.Fatal("Third element is not a/file/here")
-	}
-	if di[3] != "lastfile" {
-		t.Fatal("Fourth element is not lastfile")
-	}
-	if di[4] != "!inverted/abs/path" {
-		t.Fatal("Fifth element is not !inverted/abs/path")
-	}
-	if di[5] != "!" {
-		t.Fatalf("Sixth element is not !, but %s", di[5])
-	}
-	if di[6] != "!" {
-		t.Fatalf("Seventh element is not !, but %s", di[6])
+	if len(actual) != len(expected) {
+		t.Errorf("Expected %d entries, got %v", len(expected), len(actual))
+	}
+	for i, expectedLine := range expected {
+		if i >= len(actual) {
+			t.Errorf(`missing line %d: expected: "%s", got none`, i+1, expectedLine)
+			continue
+		}
+		if actual[i] != expectedLine {
+			t.Errorf(`line %d: expected: "%s", got: "%s"`, i+1, expectedLine, actual[i])
+		}
 	}
 }

frontend/dockerui/config.go

@@ -80,7 +80,8 @@ type Client struct {
 	g           flightcontrol.Group[*buildContext]
 	bopts       client.BuildOpts
 
-	dockerignore []byte
+	dockerignore     []byte
+	dockerignoreName string
 }
 
 type SBOM struct {
@@ -375,6 +376,7 @@ func (bc *Client) ReadEntrypoint(ctx context.Context, lang string, opts ...llb.L
 	})
 	if err == nil {
 		bc.dockerignore = dt
+		bc.dockerignoreName = bctx.filename + ".dockerignore"
 	}
 
 	return &Source{
@@ -435,13 +437,14 @@ func (bc *Client) MainContext(ctx context.Context, opts ...llb.LocalOption) (*ll
 			dt = []byte{}
 		}
 		bc.dockerignore = dt
+		bc.dockerignoreName = DefaultDockerignoreName
 	}
 
 	var excludes []string
 	if len(bc.dockerignore) != 0 {
 		excludes, err = dockerignore.ReadAll(bytes.NewBuffer(bc.dockerignore))
 		if err != nil {
-			return nil, errors.Wrap(err, "failed to parse dockerignore")
+			return nil, errors.Wrapf(err, "failed parsing %s", bc.dockerignoreName)
 		}
 	}
 

frontend/dockerui/namedcontext.go

@@ -208,7 +208,7 @@ func (bc *Client) namedContextRecursive(ctx context.Context, name string, nameWi
 			if len(dt) != 0 {
 				excludes, err = dockerignore.ReadAll(bytes.NewBuffer(dt))
 				if err != nil {
-					return nil, nil, err
+					return nil, nil, errors.Wrapf(err, "failed parsing %s", DefaultDockerignoreName)
 				}
 			}
 		}