dockerfile: add hint suggestions to UndefinedVar

Signed-off-by: Tonis Tiigi <[email protected]>

frontend/dockerfile/dockerfile2llb/convert.go

@@ -766,7 +766,7 @@ func dispatch(d *dispatchState, cmd command, opt dispatchOpt) error {
 			}
 
 			newword, unmatched, err := opt.shlex.ProcessWord(word, env)
-			reportUnmatchedVariables(cmd, d.buildArgs, unmatched, &opt)
+			reportUnmatchedVariables(cmd, d.buildArgs, env, unmatched, &opt)
 			return newword, err
 		})
 		if err != nil {
@@ -782,7 +782,7 @@ func dispatch(d *dispatchState, cmd command, opt dispatchOpt) error {
 			lex := shell.NewLex('\\')
 			lex.SkipProcessQuotes = true
 			newword, unmatched, err := lex.ProcessWord(word, env)
-			reportUnmatchedVariables(cmd, d.buildArgs, unmatched, &opt)
+			reportUnmatchedVariables(cmd, d.buildArgs, env, unmatched, &opt)
 			return newword, err
 		})
 		if err != nil {
@@ -2103,19 +2103,25 @@ func validateStageNames(stages []instructions.Stage, warn linter.LintWarnFunc) {
 	}
 }
 
-func reportUnmatchedVariables(cmd instructions.Command, buildArgs []instructions.KeyValuePairOptional, unmatched map[string]struct{}, opt *dispatchOpt) {
+func reportUnmatchedVariables(cmd instructions.Command, buildArgs []instructions.KeyValuePairOptional, env []string, unmatched map[string]struct{}, opt *dispatchOpt) {
+	for _, buildArg := range buildArgs {
+		delete(unmatched, buildArg.Key)
+	}
 	if len(unmatched) == 0 {
 		return
 	}
-	for _, buildArg := range buildArgs {
-		delete(unmatched, buildArg.Key)
+	options := metaArgsKeys(opt.metaArgs)
+	for _, envVar := range env {
+		key, _ := parseKeyValue(envVar)
+		options = append(options, key)
 	}
 	for cmdVar := range unmatched {
-		_, nonEnvOk := nonEnvArgs[cmdVar]
-		if !nonEnvOk {
-			msg := linter.RuleUndefinedVar.Format(cmdVar)
-			linter.RuleUndefinedVar.Run(opt.lintWarn, cmd.Location(), msg)
+		if _, nonEnvOk := nonEnvArgs[cmdVar]; nonEnvOk {
+			continue
 		}
+		match, _ := suggest.Search(cmdVar, options, true)
+		msg := linter.RuleUndefinedVar.Format(cmdVar, match)
+		linter.RuleUndefinedVar.Run(opt.lintWarn, cmd.Location(), msg)
 	}
 }
 

frontend/dockerfile/dockerfile_lint_test.go

@@ -582,6 +582,43 @@ RUN echo $foo
 			},
 		},
 	})
+
+	dockerfile = []byte(`
+FROM alpine
+ARG DIR_BINARIES=binaries/
+ARG DIR_ASSETS=assets/
+ARG DIR_CONFIG=config/
+COPY $DIR_ASSET .
+	`)
+	checkLinterWarnings(t, sb, &lintTestParams{
+		Dockerfile: dockerfile,
+		Warnings: []expectedLintWarning{
+			{
+				RuleName:    "UndefinedVar",
+				Description: "Variables should be defined before their use",
+				Detail:      "Usage of undefined variable '$DIR_ASSET' (did you mean $DIR_ASSETS?)",
+				Level:       1,
+				Line:        6,
+			},
+		},
+	})
+
+	dockerfile = []byte(`
+FROM alpine
+ENV PATH=$PAHT:/tmp/bin
+		`)
+	checkLinterWarnings(t, sb, &lintTestParams{
+		Dockerfile: dockerfile,
+		Warnings: []expectedLintWarning{
+			{
+				RuleName:    "UndefinedVar",
+				Description: "Variables should be defined before their use",
+				Detail:      "Usage of undefined variable '$PAHT' (did you mean $PATH?)",
+				Level:       1,
+				Line:        3,
+			},
+		},
+	})
 }
 
 func testMultipleInstructionsDisallowed(t *testing.T, sb integration.Sandbox) {

frontend/dockerfile/linter/ruleset.go

@@ -95,11 +95,15 @@ var (
 			return fmt.Sprintf("Usage of undefined variable '$%s'", arg)
 		},
 	}
-	RuleUndefinedVar = LinterRule[func(string) string]{
+	RuleUndefinedVar = LinterRule[func(string, string) string]{
 		Name:        "UndefinedVar",
 		Description: "Variables should be defined before their use",
-		Format: func(arg string) string {
-			return fmt.Sprintf("Usage of undefined variable '$%s'", arg)
+		Format: func(arg, suggest string) string {
+			out := fmt.Sprintf("Usage of undefined variable '$%s'", arg)
+			if suggest != "" {
+				out += fmt.Sprintf(" (did you mean $%s?)", suggest)
+			}
+			return out
 		},
 	}
 	RuleMultipleInstructionsDisallowed = LinterRule[func(instructionName string) string]{