dockerfile: improve error messages and add suggest to platform flag p…

…arsing

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

frontend/dockerfile/dockerfile2llb/convert.go

@@ -291,9 +291,18 @@ func toDispatchState(ctx context.Context, dt []byte, opt ConvertOpt) (*dispatchS
 				return nil, parser.WithLocation(errors.Wrapf(err, "failed to process arguments for platform %s", platMatch.Result), st.Location)
 			}
 
+			if platMatch.Result == "" {
+				err := errors.Errorf("empty platform value from expression %s", v)
+				err = parser.WithLocation(err, st.Location)
+				err = wrapSuggestAny(err, platMatch.Unmatched, metaArgsKeys(optMetaArgs))
+				return nil, err
+			}
+
 			p, err := platforms.Parse(platMatch.Result)
 			if err != nil {
-				return nil, parser.WithLocation(errors.Wrapf(err, "failed to parse platform %s", platMatch.Result), st.Location)
+				err = parser.WithLocation(err, st.Location)
+				err = wrapSuggestAny(err, platMatch.Unmatched, metaArgsKeys(optMetaArgs))
+				return nil, parser.WithLocation(errors.Wrapf(err, "failed to parse platform %s", v), st.Location)
 			}
 
 			for k := range platMatch.Matched {
@@ -687,6 +696,14 @@ func metaArgsToMap(metaArgs []instructions.KeyValuePairOptional) map[string]stri
 	return m
 }
 
+func metaArgsKeys(metaArgs []instructions.KeyValuePairOptional) []string {
+	s := make([]string, 0, len(metaArgs))
+	for _, arg := range metaArgs {
+		s = append(s, arg.Key)
+	}
+	return s
+}
+
 func toCommand(ic instructions.Command, allDispatchStates *dispatchStates) (command, error) {
 	cmd := command{Command: ic}
 	if c, ok := ic.(*instructions.CopyCommand); ok {
@@ -2178,3 +2195,14 @@ func validateUsedOnce(c instructions.Command, loc *instructionTracker, warn lint
 	}
 	loc.MarkUsed(c.Location())
 }
+
+func wrapSuggestAny(err error, keys map[string]struct{}, options []string) error {
+	for k := range keys {
+		var ok bool
+		err, ok = suggest.WrapErrorMaybe(err, k, options, true)
+		if ok {
+			break
+		}
+	}
+	return err
+}

frontend/dockerfile/dockerfile_lint_test.go

@@ -467,11 +467,33 @@ COPY Dockerfile .
 				Line:        2,
 			},
 		},
-		StreamBuildErr:    "failed to solve: failed to parse platform : \"\" is an invalid component of \"\": platform specifier component must match \"^[A-Za-z0-9_-]+$\": invalid argument",
-		UnmarshalBuildErr: "failed to parse platform : \"\" is an invalid component of \"\": platform specifier component must match \"^[A-Za-z0-9_-]+$\": invalid argument",
+		StreamBuildErr:    "failed to solve: empty platform value from expression $BULIDPLATFORM (did you mean BUILDPLATFORM?)",
+		UnmarshalBuildErr: "empty platform value from expression $BULIDPLATFORM (did you mean BUILDPLATFORM?)",
 		BuildErrLocation:  2,
 	})
 
+	dockerfile = []byte(`
+ARG MY_OS=linux
+ARG MY_ARCH=amd64
+FROM --platform=linux/${MYARCH} busybox
+COPY Dockerfile .
+	`)
+	checkLinterWarnings(t, sb, &lintTestParams{
+		Dockerfile: dockerfile,
+		Warnings: []expectedLintWarning{
+			{
+				RuleName:    "UndeclaredArgInFrom",
+				Description: "FROM command must use declared ARGs",
+				Detail:      "FROM argument 'MYARCH' is not declared",
+				Level:       1,
+				Line:        4,
+			},
+		},
+		StreamBuildErr:    "failed to solve: failed to parse platform linux/: \"\" is an invalid component of \"linux/\": platform specifier component must match \"^[A-Za-z0-9_-]+$\": invalid argument (did you mean MY_ARCH?)",
+		UnmarshalBuildErr: "failed to parse platform linux/: \"\" is an invalid component of \"linux/\": platform specifier component must match \"^[A-Za-z0-9_-]+$\": invalid argument (did you mean MY_ARCH?)",
+		BuildErrLocation:  4,
+	})
+
 	dockerfile = []byte(`
 ARG tag=latest
 FROM busybox:${tag}${version} AS b

util/suggest/error.go

@@ -8,8 +8,13 @@ import (
 
 // WrapError wraps error with a suggestion for fixing it
 func WrapError(err error, val string, options []string, caseSensitive bool) error {
+	err, _ = WrapErrorMaybe(err, val, options, caseSensitive)
+	return err
+}
+
+func WrapErrorMaybe(err error, val string, options []string, caseSensitive bool) (error, bool) {
 	if err == nil {
-		return nil
+		return nil, false
 	}
 	orig := val
 	if !caseSensitive {
@@ -23,7 +28,7 @@ func WrapError(err error, val string, options []string, caseSensitive bool) erro
 		}
 		if val == opt {
 			// exact match means error was unrelated to the value
-			return err
+			return err, false
 		}
 		dist := levenshtein.Distance(val, opt, nil)
 		if dist < mindist {
@@ -37,13 +42,13 @@ func WrapError(err error, val string, options []string, caseSensitive bool) erro
 	}
 
 	if match == "" {
-		return err
+		return err, false
 	}
 
 	return &suggestError{
 		err:   err,
 		match: match,
-	}
+	}, true
 }
 
 type suggestError struct {