add test checking for a build-arg overwrite

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

frontend/dockerfile/dockerfile2llb/convert.go

@@ -717,9 +717,9 @@ func toDispatchState(ctx context.Context, dt []byte, opt ConvertOpt) (*dispatchS
 	}
 
 	// If lint.Error() returns an error, it means that
-	// error if there were warnings, and that our linter has been
-	// configured to return an error on warnings, so we appropriately return
-	// that error here.
+	// there were warnings, and that our linter has been
+	// configured to return an error on warnings,
+	// so we appropriately return that error here.
 	err = lint.Error()
 	if err != nil {
 		return nil, err

frontend/dockerfile/dockerfile_lint_test.go

@@ -101,6 +101,40 @@ copy Dockerfile .
 		UnmarshalBuildErr: "lint violation found for rules: FromAsCasing",
 		BuildErrLocation:  2,
 	})
+
+	dockerfile = []byte(`#check=skip=all
+FROM scratch as base
+copy Dockerfile .
+`)
+	checkLinterWarnings(t, sb, &lintTestParams{
+		Dockerfile: dockerfile,
+		Warnings: []expectedLintWarning{
+			{
+				RuleName:    "FromAsCasing",
+				Description: "The 'as' keyword should match the case of the 'from' keyword",
+				Detail:      "'as' and 'FROM' keywords' casing do not match",
+				Line:        2,
+				Level:       1,
+			},
+		},
+		StreamBuildErr:    "failed to solve: lint violation found for rules: FromAsCasing",
+		UnmarshalBuildErr: "lint violation found for rules: FromAsCasing",
+		BuildErrLocation:  2,
+		FrontendAttrs: map[string]string{
+			"build-arg:BUILDKIT_DOCKERFILE_LINT": "skip=FileConsistentCommandCasing;error=true",
+		},
+	})
+
+	dockerfile = []byte(`#check=error=true
+FROM scratch as base
+copy Dockerfile .
+`)
+	checkLinterWarnings(t, sb, &lintTestParams{
+		Dockerfile: dockerfile,
+		FrontendAttrs: map[string]string{
+			"build-arg:BUILDKIT_DOCKERFILE_LINT": "skip=all",
+		},
+	})
 }
 
 func testStageName(t *testing.T, sb integration.Sandbox) {
@@ -793,12 +827,16 @@ func checkUnmarshal(t *testing.T, sb integration.Sandbox, lintTest *lintTestPara
 
 	called := false
 	frontend := func(ctx context.Context, c gateway.Client) (*gateway.Result, error) {
+		frontendOpts := map[string]string{
+			"frontend.caps": "moby.buildkit.frontend.subrequests",
+			"requestid":     "frontend.lint",
+		}
+		for k, v := range lintTest.FrontendAttrs {
+			frontendOpts[k] = v
+		}
 		res, err := c.Solve(ctx, gateway.SolveRequest{
-			FrontendOpt: map[string]string{
-				"frontend.caps": "moby.buildkit.frontend.subrequests",
-				"requestid":     "frontend.lint",
-			},
-			Frontend: "dockerfile.v0",
+			FrontendOpt: frontendOpts,
+			Frontend:    "dockerfile.v0",
 		})
 		if err != nil {
 			return nil, err
@@ -864,9 +902,7 @@ func checkProgressStream(t *testing.T, sb integration.Sandbox, lintTest *lintTes
 	f := getFrontend(t, sb)
 
 	_, err := f.Solve(sb.Context(), lintTest.Client, client.SolveOpt{
-		FrontendAttrs: map[string]string{
-			"platform": "linux/amd64,linux/arm64",
-		},
+		FrontendAttrs: lintTest.FrontendAttrs,
 		LocalMounts: map[string]fsutil.FS{
 			dockerui.DefaultLocalNameDockerfile: lintTest.TmpDir,
 			dockerui.DefaultLocalNameContext:    lintTest.TmpDir,
@@ -884,14 +920,6 @@ func checkProgressStream(t *testing.T, sb integration.Sandbox, lintTest *lintTes
 		t.Fatalf("timed out waiting for statusDone")
 	}
 
-	// two platforms only show one warning
-	if len(lintTest.Warnings) != len(warnings) {
-		// print warnings for debugging
-		for _, w := range warnings {
-			t.Logf("received warning: %q", w.Short)
-		}
-	}
-
 	require.Equal(t, len(lintTest.Warnings), len(warnings))
 	sort.Slice(warnings, func(i, j int) bool {
 		w1 := warnings[i]
@@ -985,4 +1013,5 @@ type lintTestParams struct {
 	StreamBuildErr    string
 	UnmarshalBuildErr string
 	BuildErrLocation  int32
+	FrontendAttrs     map[string]string
 }