Add parse only evaluation to REPL

repl/commands.go

@@ -102,7 +102,8 @@ type parseCmd struct {
 }
 
 type evalCmd struct {
-	expr string
+	parseOnly bool
+	expr      string
 }
 
 // Cmder interface provides normalized command name from a repl command.
@@ -308,7 +309,18 @@ func (c *commandParseListener) EnterParse(ctx *parser.ParseContext) {
 }
 
 func (c *commandParseListener) EnterExprCmd(ctx *parser.ExprCmdContext) {
-	c.cmd = &evalCmd{}
+	cmd := &evalCmd{}
+	for _, f := range ctx.GetFlags() {
+		ft := strings.TrimPrefix(strings.TrimPrefix(f.GetText(), "--"), "-")
+		switch ft {
+		case "parse-only":
+			cmd.parseOnly = true
+		default:
+			c.reportIssue(fmt.Errorf("unknown or unsupported flag: %q", ft))
+			return
+		}
+	}
+	c.cmd = cmd
 }
 
 func (c *commandParseListener) ExitFnDecl(ctx *parser.FnDeclContext) {

repl/commands_test.go

@@ -203,10 +203,10 @@ func TestParse(t *testing.T) {
             %exit`),
 		},
 		{
-			commandLine: `%arbitrary --flag -FLAG 'string literal\n'`,
+			commandLine: `%arbitrary --flag --another-flag 'string literal\n'`,
 			wantCmd: &simpleCmd{cmd: "arbitrary",
 				args: []string{
-					"--flag", "--flag", "string literal\\n",
+					"--flag", "--another-flag", "string literal\\n",
 				},
 			},
 		},
@@ -284,6 +284,13 @@ func TestParse(t *testing.T) {
 				src:        "",
 			},
 		},
+		{
+			commandLine: `%eval --parse-only -- foo`,
+			wantCmd: &evalCmd{
+				parseOnly: true,
+				expr:      `foo`,
+			},
+		},
 	}
 
 	for _, tc := range testCases {
@@ -344,6 +351,24 @@ func TestParseErrors(t *testing.T) {
 			// not an identifier
 			commandLine: "%delete 123",
 		},
+		{
+			commandLine: "%eval --badflag foo",
+		},
+		{
+			commandLine: "%eval --bad-flag foo",
+		},
+		{
+			commandLine: "%eval -badflag foo",
+		},
+		{
+			commandLine: "%eval -bad-flag foo",
+		},
+		{
+			commandLine: "%eval --parse-only foo",
+		},
+		{
+			commandLine: "%eval -parse-only foo",
+		},
 	}
 	for _, tc := range testCases {
 		_, err := Parse(tc.commandLine)

repl/evaluator.go

@@ -1302,16 +1302,28 @@ func (e *Evaluator) Process(cmd Cmder) (string, bool, error) {
 		}
 		return prototext.Format(pAST), false, nil
 	case *evalCmd:
-		val, resultT, err := e.Evaluate(cmd.expr)
+		var (
+			val     ref.Val
+			resultT *exprpb.Type
+			err     error
+		)
+		if cmd.parseOnly {
+			val, resultT, err = e.EvaluateParseOnly(cmd.expr)
+		} else {
+			val, resultT, err = e.Evaluate(cmd.expr)
+		}
 		if err != nil {
 			return "", false, fmt.Errorf("expr failed:\n%v", err)
 		}
 		if val != nil {
-			t := UnparseType(resultT)
 			unknown, ok := val.Value().(*types.Unknown)
 			if ok {
 				return fmt.Sprintf("Unknown %v", unknown), false, nil
 			}
+			if cmd.parseOnly {
+				return fmt.Sprintf("%s", types.Format(val)), false, nil
+			}
+			t := UnparseType(resultT)
 			return fmt.Sprintf("%s : %s", types.Format(val), t), false, nil
 		}
 	case *letVarCmd:
@@ -1394,6 +1406,29 @@ func (e *Evaluator) Evaluate(expr string) (ref.Val, *exprpb.Type, error) {
 	return val, ast.ResultType(), err
 }
 
+// EvaluateParseOnly evalutes the CEL expression using the current REPL context without type checking.
+func (e *Evaluator) EvaluateParseOnly(expr string) (ref.Val, *exprpb.Type, error) {
+	env, act, err := e.applyContext()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	ast, iss := env.Parse(expr)
+	if iss.Err() != nil {
+		return nil, nil, iss.Err()
+	}
+
+	p, err := env.Program(ast, e.ctx.programOptions()...)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	act, _ = env.PartialVars(act)
+	val, _, err := p.Eval(act)
+	// expression can be well-formed and result in an error
+	return val, ast.ResultType(), err
+}
+
 // Compile compiles the input expression using the current REPL context.
 func (e *Evaluator) Compile(expr string) (*cel.Ast, error) {
 	env, _, err := e.applyContext()

repl/parser/Commands.g4

@@ -51,7 +51,7 @@ compile: '%compile' e=expr;
 
 parse: '%parse' e=expr;
 
-exprCmd: '%eval'? e=expr;
+exprCmd: ('%eval' (flags+=FLAG (flags+=FLAG)* '--')?)? e=expr;
 
 qualId: leadingDot='.'? rid=IDENTIFIER ('.' qualifiers+=IDENTIFIER)*;
 
@@ -69,6 +69,6 @@ typeParamList:
 
 // lexer rules:
 COMMAND: '%' IDENTIFIER;
-FLAG: '-'? '-' IDENTIFIER;
+FLAG: '-' ('-' IDENTIFIER)+;
 ARROW: '->';
 EQUAL_ASSIGN: '=';

repl/parser/Commands.tokens

@@ -6,47 +6,48 @@ T__4=5
 T__5=6
 T__6=7
 T__7=8
-COMMAND=9
-FLAG=10
-ARROW=11
-EQUAL_ASSIGN=12
-EQUALS=13
-NOT_EQUALS=14
-IN=15
-LESS=16
-LESS_EQUALS=17
-GREATER_EQUALS=18
-GREATER=19
-LOGICAL_AND=20
-LOGICAL_OR=21
-LBRACKET=22
-RPRACKET=23
-LBRACE=24
-RBRACE=25
-LPAREN=26
-RPAREN=27
-DOT=28
-COMMA=29
-MINUS=30
-EXCLAM=31
-QUESTIONMARK=32
-COLON=33
-PLUS=34
-STAR=35
-SLASH=36
-PERCENT=37
-CEL_TRUE=38
-CEL_FALSE=39
-NUL=40
-WHITESPACE=41
-COMMENT=42
-NUM_FLOAT=43
-NUM_INT=44
-NUM_UINT=45
-STRING=46
-BYTES=47
-IDENTIFIER=48
-ESC_IDENTIFIER=49
+T__8=9
+COMMAND=10
+FLAG=11
+ARROW=12
+EQUAL_ASSIGN=13
+EQUALS=14
+NOT_EQUALS=15
+IN=16
+LESS=17
+LESS_EQUALS=18
+GREATER_EQUALS=19
+GREATER=20
+LOGICAL_AND=21
+LOGICAL_OR=22
+LBRACKET=23
+RPRACKET=24
+LBRACE=25
+RBRACE=26
+LPAREN=27
+RPAREN=28
+DOT=29
+COMMA=30
+MINUS=31
+EXCLAM=32
+QUESTIONMARK=33
+COLON=34
+PLUS=35
+STAR=36
+SLASH=37
+PERCENT=38
+CEL_TRUE=39
+CEL_FALSE=40
+NUL=41
+WHITESPACE=42
+COMMENT=43
+NUM_FLOAT=44
+NUM_INT=45
+NUM_UINT=46
+STRING=47
+BYTES=48
+IDENTIFIER=49
+ESC_IDENTIFIER=50
 '%help'=1
 '%?'=2
 '%let'=3
@@ -55,33 +56,34 @@ ESC_IDENTIFIER=49
 '%compile'=6
 '%parse'=7
 '%eval'=8
-'->'=11
-'='=12
-'=='=13
-'!='=14
-'in'=15
-'<'=16
-'<='=17
-'>='=18
-'>'=19
-'&&'=20
-'||'=21
-'['=22
-']'=23
-'{'=24
-'}'=25
-'('=26
-')'=27
-'.'=28
-','=29
-'-'=30
-'!'=31
-'?'=32
-':'=33
-'+'=34
-'*'=35
-'/'=36
-'%'=37
-'true'=38
-'false'=39
-'null'=40
+'--'=9
+'->'=12
+'='=13
+'=='=14
+'!='=15
+'in'=16
+'<'=17
+'<='=18
+'>='=19
+'>'=20
+'&&'=21
+'||'=22
+'['=23
+']'=24
+'{'=25
+'}'=26
+'('=27
+')'=28
+'.'=29
+','=30
+'-'=31
+'!'=32
+'?'=33
+':'=34
+'+'=35
+'*'=36
+'/'=37
+'%'=38
+'true'=39
+'false'=40
+'null'=41