frontend/dockerfile: add RunCommand.FlagsUsed field

frontend/dockerfile/instructions/bflag.go

@@ -108,6 +108,15 @@ func (fl *Flag) IsUsed() bool {
 	return false
 }
 
+// Used returns a slice of flag names that are set
+func (bf *BFlags) Used() []string {
+	used := make([]string, 0, len(bf.used))
+	for f := range bf.used {
+		used = append(used, f)
+	}
+	return used
+}
+
 // IsTrue checks if a bool flag is true
 func (fl *Flag) IsTrue() bool {
 	if fl.flagType != boolType {

frontend/dockerfile/instructions/bflag_test.go

@@ -1,6 +1,8 @@
 package instructions
 
 import (
+	"sort"
+	"strings"
 	"testing"
 )
 
@@ -184,4 +186,30 @@ func TestBuilderFlags(t *testing.T) {
 	if !flBool1.IsTrue() {
 		t.Fatalf("Test %s, bool1 should be true", bf.Args)
 	}
+
+	// ---
+
+	bf = NewBFlags()
+	_ = bf.AddBool("bool1", false)
+	_ = bf.AddBool("bool2", false)
+	_ = bf.AddBool("bool3", false)
+	_ = bf.AddBool("bool4", true)
+	_ = bf.AddBool("bool5", true)
+	_ = bf.AddString("str1", "")
+	_ = bf.AddString("str2", "")
+	_ = bf.AddString("str3", "def3")
+	_ = bf.AddString("str4", "def4")
+
+	bf.Args = []string{`--bool2=false`, `--bool3`, `--bool4=true`, `--bool5`, `--str2= `, `--str3=def3`, `--str4=my-val`}
+
+	if err = bf.Parse(); err != nil {
+		t.Fatalf("Test %q was supposed to work: %s", bf.Args, err)
+	}
+	used := bf.Used()
+	sort.Strings(used)
+	expected = "bool2, bool3, bool4, bool5, str2, str3, str4"
+	actual := strings.Join(used, ", ")
+	if actual != expected {
+		t.Fatalf("Test %s, expected '%s', got '%s'", bf.Args, expected, actual)
+	}
 }

frontend/dockerfile/instructions/commands.go

@@ -269,6 +269,7 @@ type RunCommand struct {
 	withNameAndCode
 	withExternalData
 	ShellDependantCmdLine
+	FlagsUsed []string
 }
 
 // CmdCommand : CMD foo

frontend/dockerfile/instructions/parse.go

@@ -375,7 +375,7 @@ func parseRun(req parseRequest) (*RunCommand, error) {
 	if err := req.flags.Parse(); err != nil {
 		return nil, err
 	}
-
+	cmd.FlagsUsed = req.flags.Used()
 	cmd.ShellDependantCmdLine = parseShellDependentCommand(req, false)
 	cmd.withNameAndCode = newWithNameAndCode(req)
 

frontend/dockerfile/instructions/parse_test.go

@@ -226,3 +226,16 @@ func TestErrorCases(t *testing.T) {
 		require.Contains(t, err.Error(), c.expectedError)
 	}
 }
+
+func TestRunCmdFlagsUsed(t *testing.T) {
+	dockerfile := "RUN --mount=type=tmpfs,target=/foo/ echo hello"
+	r := strings.NewReader(dockerfile)
+	ast, err := parser.Parse(r)
+	require.NoError(t, err)
+
+	n := ast.AST.Children[0]
+	c, err := ParseInstruction(n)
+	require.NoError(t, err)
+	require.IsType(t, c, &RunCommand{})
+	require.Equal(t, []string{"mount"}, c.(*RunCommand).FlagsUsed)
+}