Add nil args to env list as empty strings when calling buildMetaArgs

Signed-off-by: Talon Bowler <talon.bowler@docker.com>

frontend/dockerfile/dockerfile2llb/convert.go

@@ -263,16 +263,15 @@ func toDispatchState(ctx context.Context, dt []byte, opt ConvertOpt) (*dispatchS
 	shlex := shell.NewLex(dockerfile.EscapeToken)
 	outline := newOutlineCapture()
 
-	// Validate that base images continue to be valid even
-	// when no build arguments are used.
-	validateBaseImagesWithDefaultArgs(stages, shlex, argCmds, globalArgs, lint)
-
 	// Rebuild the arguments using the provided build arguments
 	// for the remainder of the build.
 	globalArgs, outline.allArgs, err = buildMetaArgs(globalArgs, shlex, argCmds, opt.BuildArgs)
 	if err != nil {
 		return nil, err
 	}
+	// Validate that base images continue to be valid even
+	// when no build arguments are used.
+	validateBaseImagesWithDefaultArgs(stages, shlex, outline.allArgs, lint)
 
 	metaResolver := opt.MetaResolver
 	if metaResolver == nil {
@@ -284,7 +283,7 @@ func toDispatchState(ctx context.Context, dt []byte, opt ConvertOpt) (*dispatchS
 	// set base state for every image
 	for i, st := range stages {
 		nameMatch, err := shlex.ProcessWordWithMatches(st.BaseName, globalArgs)
-		reportUnusedFromArgs(globalArgs, nameMatch.Unmatched, st.Location, lint)
+		reportUnusedFromArgs(outline.allArgs, nameMatch.Unmatched, st.Location, lint)
 		used := nameMatch.Matched
 		if used == nil {
 			used = map[string]struct{}{}
@@ -311,7 +310,7 @@ func toDispatchState(ctx context.Context, dt []byte, opt ConvertOpt) (*dispatchS
 
 		if v := st.Platform; v != "" {
 			platMatch, err := shlex.ProcessWordWithMatches(v, globalArgs)
-			reportUnusedFromArgs(globalArgs, platMatch.Unmatched, st.Location, lint)
+			reportUnusedFromArgs(outline.allArgs, platMatch.Unmatched, st.Location, lint)
 			reportRedundantTargetPlatform(st.Platform, platMatch, st.Location, globalArgs, lint)
 			reportConstPlatformDisallowed(st.Name, platMatch, st.Location, lint)
 
@@ -2332,9 +2331,16 @@ func toPBLocation(sourceIndex int, location []parser.Range) pb.Location {
 	}
 }
 
-func reportUnusedFromArgs(args shell.EnvGetter, unmatched map[string]struct{}, location []parser.Range, lint *linter.Linter) {
+func reportUnusedFromArgs(args map[string]argInfo, unmatched map[string]struct{}, location []parser.Range, lint *linter.Linter) {
+	argKeys := make([]string, 0, len(args))
+	for k := range args {
+		argKeys = append(argKeys, k)
+	}
 	for arg := range unmatched {
-		suggest, _ := suggest.Search(arg, args.Keys(), true)
+		if _, ok := args[arg]; ok {
+			continue
+		}
+		suggest, _ := suggest.Search(arg, argKeys, true)
 		msg := linter.RuleUndefinedArgInFrom.Format(arg, suggest)
 		lint.Run(&linter.RuleUndefinedArgInFrom, location, msg)
 	}
@@ -2456,15 +2462,10 @@ func validateNoSecretKey(instruction, key string, location []parser.Range, lint
 	}
 }
 
-func validateBaseImagesWithDefaultArgs(stages []instructions.Stage, shlex *shell.Lex, argsCmds []instructions.ArgCommand, args *llb.EnvList, lint *linter.Linter) {
-	// Build the arguments as if no build options were given
-	// and using only defaults.
-	args, _, err := buildMetaArgs(args, shlex, argsCmds, nil)
-	if err != nil {
-		// Abandon running the linter. We'll likely fail after this point
-		// with the same error but we shouldn't error here inside
-		// of the linting check.
-		return
+func validateBaseImagesWithDefaultArgs(stages []instructions.Stage, shlex *shell.Lex, allArgs map[string]argInfo, lint *linter.Linter) {
+	args := &llb.EnvList{}
+	for key, info := range allArgs {
+		args = args.AddOrReplace(key, info.value)
 	}
 
 	for _, st := range stages {

frontend/dockerfile/dockerfile_lint_test.go

@@ -805,6 +805,27 @@ COPY Dockerfile .
 `)
 	checkLinterWarnings(t, sb, &lintTestParams{Dockerfile: dockerfile})
 
+	dockerfile = []byte(`
+ARG DEBUG
+FROM scratch${DEBUG}
+COPY Dockerfile .
+`)
+	checkLinterWarnings(t, sb, &lintTestParams{Dockerfile: dockerfile})
+
+	dockerfile = []byte(`
+ARG DEBUG
+FROM scra${DEBUG:-tch}
+COPY Dockerfile .
+`)
+	checkLinterWarnings(t, sb, &lintTestParams{Dockerfile: dockerfile})
+
+	dockerfile = []byte(`
+ARG DEBUG=""
+FROM scratch${DEBUG-@bogus}
+COPY Dockerfile .
+`)
+	checkLinterWarnings(t, sb, &lintTestParams{Dockerfile: dockerfile})
+
 	dockerfile = []byte(`
 FROM --platform=$BULIDPLATFORM scratch
 COPY Dockerfile .
@@ -1456,6 +1477,9 @@ func checkProgressStream(t *testing.T, sb integration.Sandbox, lintTest *lintTes
 		},
 	}, status)
 	if lintTest.StreamBuildErr == "" && lintTest.StreamBuildErrRegexp == nil {
+		if err != nil {
+			t.Logf("expected no error, received: %v", err)
+		}
 		require.NoError(t, err)
 	} else {
 		if lintTest.StreamBuildErr != "" {
@@ -1471,6 +1495,13 @@ func checkProgressStream(t *testing.T, sb integration.Sandbox, lintTest *lintTes
 		t.Fatalf("timed out waiting for statusDone")
 	}
 
+	if len(lintTest.Warnings) != len(warnings) {
+		t.Logf("expected %d warnings, received:", len(lintTest.Warnings))
+		for i, w := range warnings {
+			t.Logf("\t%d: %s", i, w.Short)
+		}
+
+	}
 	require.Equal(t, len(lintTest.Warnings), len(warnings))
 	sort.Slice(warnings, func(i, j int) bool {
 		w1 := warnings[i]