waiig15/parser/parser_test.go

package parser

import (
	"testing"

	"fmt"

	"code.osinet.fr/fgm/waiig15/ast"
	"code.osinet.fr/fgm/waiig15/lexer"
)

func TestLetStatements(t *testing.T) {
	// Try removing the ident, the =, or both, to get human-readable errors.
	input := `
let x = 5;
let y = 10;
let foobar = 838383;
`
	l := lexer.New(input)
	p := New(l)

	program := p.ParseProgram()
	checkParserErrors(t, p)
	if program == nil {
		t.Fatalf("ParseProgram() returned nil.")
	}

	if len(program.Statements) != 3 {
		t.Fatalf("program.Statements does not contain 3 statements, got=%d",
			len(program.Statements))
	}

	tests := []struct {
		expectedIdentifier string
	}{
		{"x"},
		{"y"},
		{"foobar"},
	}

	for i, tt := range tests {
		stmt := program.Statements[i]
		if !testLetStatement(t, stmt, tt.expectedIdentifier) {
			return
		}
	}
}

func TestReturnStatements(t *testing.T) {
	// Try removing the ident, the =, or both, to get human-readable errors.
	input := `
return 5;
return 10;
return 993322;
`
	l := lexer.New(input)
	p := New(l)

	program := p.ParseProgram()
	checkParserErrors(t, p)
	if program == nil {
		t.Fatalf("ParseProgram() returned nil.")
	}

	if len(program.Statements) != 3 {
		t.Fatalf("program.Statements does not contain 3 statements, got=%d",
			len(program.Statements))
	}

	for _, stmt := range program.Statements {
		// Statement is an interface, we need a concrete type for the value, and
		// our test input only contains Let statements.
		returnStmt, ok := stmt.(*ast.ReturnStatement)
		if !ok {
			t.Errorf("s not *ast.ReturnStatement{}, got=%T", stmt)
			continue
		}
		if returnStmt.TokenLiteral() != "return" {
			t.Errorf("s.TokenLiteral not 'return', got=%q",
				stmt.TokenLiteral())
		}
	}
}

func TestIdentifierExpression(t *testing.T) {
	const input = "foobar"

	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParserErrors(t, p)

	if len(program.Statements) != 1 {
		t.Fatalf("program has not enough statements. got=%d",
			len(program.Statements))
	}

	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
	if !ok {
		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. Got=%T",
			program.Statements)
	}

	ident, ok := stmt.Expression.(*ast.Identifier)
	if !ok {
		t.Fatalf("exp not *ast.Identifier. got=%T", stmt.Expression)
	}

	// Why not use input instead of inline strings ?
	if ident.Value != input {
		t.Errorf("ident.Value not %s. got=%s", input,
			ident.Value)
	}
	if ident.TokenLiteral() != input {
		t.Errorf("ident.TokenLiteral not %s. got=%s", input,
			ident.TokenLiteral())
	}
}

func TestIntegerLiteralExpression(t *testing.T) {
	input := "5;"

	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParserErrors(t, p)

	if len(program.Statements) != 1 {
		t.Fatalf("program does not have 1 statement. got=%d",
			len(program.Statements))
	}
	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
	if !ok {
		t.Fatalf("program.Statements[0] is not *ast.ExpressionStatement. got=%T",
			program.Statements[0])
	}

	literal, ok := stmt.Expression.(*ast.IntegerLiteral)
	if !ok {
		t.Fatalf("exp not *ast.IntegerLiteral. got=%T", stmt.Expression)
	}
	if literal.Value != 5 {
		t.Errorf("literal.Value not %d. got=%d", 5, literal.Value)
	}
	if literal.TokenLiteral() != "5" {
		t.Errorf("literal.TokenLiteral not %s. got=%s", "5",
			literal.TokenLiteral())
	}
}

func TestParsingPrefixExpressions(t *testing.T) {
	prefixTests := []struct {
		input        string
		operator     string
		integerValue int64
	}{
		{"!5", "!", 5},
		{"-15", "-", 15},
	}

	for _, tt := range prefixTests {
		l := lexer.New(tt.input)
		p := New(l)
		program := p.ParseProgram()
		checkParserErrors(t, p)

		if len(program.Statements) != 1 {
			t.Fatalf("program.Statements does not contain %d statements, got=%d\n",
				1, len(program.Statements))
		}

		stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
		if !ok {
			t.Fatalf("program.STatements[0] is not ast.ExpressionStatement. got=%T",
				program.Statements[0])
		}

		exp, ok := stmt.Expression.(*ast.PrefixExpression)
		if !ok {
			t.Fatalf("stms is not ast.PrefixExpression. got=%T",
				stmt.Expression)
		}

		if exp.Operator != tt.operator {
			t.Fatalf("exp.Operator is not '%s'. got=%s",
				tt.operator, exp.Operator)
		}

		if !testIntegerLiteral(t, exp.Right, tt.integerValue) {
			return
		}
	}
}

func TestParsingInfixExpressions(t *testing.T) {
	infixTests := []struct {
		input      string
		leftValue  int64
		operator   string
		rightValue int64
	}{
		{"5 + 5;", 5, "+", 5},
		{"5 - 5;", 5, "-", 5},
		{"5 * 5;", 5, "*", 5},
		{"5 / 5;", 5, "/", 5},
		{"5 > 5;", 5, ">", 5},
		{"5 < 5;", 5, "<", 5},
		{"5 == 5;", 5, "==", 5},
		{"5 != 5;", 5, "!=", 5},
	}

	for _, tt := range infixTests {
		l := lexer.New(tt.input)
		p := New(l)
		program := p.ParseProgram()
		checkParserErrors(t, p)

		if len(program.Statements) != 1 {
			t.Fatalf("program.Statements does not contain %d statements. got=%d",
				1, len(program.Statements))
		}

		stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
		if !ok {
			t.Fatalf("program.Statements[0] is not expressionStatement. got=%T",
				program.Statements[0])
		}

		exp, ok := stmt.Expression.(*ast.InfixExpression)
		if !ok {
			t.Fatalf("exp is not infixExpression. got=%T", stmt.Expression)
		}

		// Why no error ?
		if !testIntegerLiteral(t, exp.Left, tt.leftValue) {
			return
		}

		if exp.Operator != tt.operator {
			t.Fatalf("exp.Operator is not '%s'. got=%s", tt.operator,
				exp.Operator)
		}

		// Why no error ?
		if !testIntegerLiteral(t, exp.Right, tt.rightValue) {
			return
		}
	}
}

func TestOperatorPrecedenceParsing(t *testing.T) {
	tests := []struct {
		input    string
		expected string
	}{
		{
			"-a * b",
			"((-a) * b)",
		},
		{
			"!-a",
			"(!(-a))",
		},
		{
			"a + b + c",
			"((a + b) + c)",
		},
		{
			"a + b - c",
			"((a + b) - c)",
		},
		{
			"a * b * c",
			"((a * b) * c)",
		},
		{
			"a * b / c",
			"((a * b) / c)",
		},
		{
			"a + b / c",
			"(a + (b / c))",
		},
		{
			"a + b * c + d / e - f",
			"(((a + (b * c)) + (d / e)) - f)",
		},
		{
			"3 + 4; -5 * 5",
			"(3 + 4)((-5) * 5)",
		},
		{
			"5 > 4 == 3 < 4",
			"((5 > 4) == (3 < 4))",
		},
		{
			"5 < 4 != 3 > 4",
			"((5 < 4) != (3 > 4))",
		},
		{
			"3 + 4 * 5 == 3 * 1 + 4 * 5",
			"((3 + (4 * 5)) == ((3 * 1) + (4 * 5)))",
		},
	}

	for _, tt := range tests {
		l := lexer.New(tt.input)
		p := New(l)
		program := p.ParseProgram()
		checkParserErrors(t, p)

		actual := program.String()
		if actual != tt.expected {
			t.Errorf("expected=%q, got=%q", tt.expected, actual)
		}
	}
}

func testLetStatement(t *testing.T, s ast.Statement, name string) bool {
	if s.TokenLiteral() != "let" {
		t.Errorf("s.TokenLiteral not 'let'. got=%q", s.TokenLiteral())
		return false
	}

	// Statement is an interface, we need a concrete type for the value, and we
	// just determined this looked like a LetStatement.
	letStmt, ok := s.(*ast.LetStatement)
	if !ok {
		t.Errorf("s not *ast.LetStatement. got=%T", s)
		return false
	}

	if letStmt.Name.Value != name {
		t.Errorf("letStmt.Name.Value not '%s'. got=%s", name, letStmt.Name.Value)
		return false
	}

	if letStmt.Name.TokenLiteral() != name {
		t.Errorf("letStmt.Name.TokenLiteral() not '%s'. got=%s",
			name, letStmt.Name.TokenLiteral())
		return false
	}

	return true
}

func testInfixExpression(
	t *testing.T,
	exp ast.Expression,
	left interface{},
	operator string,
	right interface{},
) bool {
	opExp, ok := exp.(*ast.InfixExpression)
	if !ok {
		t.Errorf("exp is not ast.InfixExpression. got=%T(%s)", exp, exp)
		return false
	}

	if !testLiteralExpression(t, opExp.Left, left) {
		return false
	}

	if opExp.Operator != operator {
		t.Errorf("exp.Operator is not '%s'. got=%q", operator, opExp.Operator)
		return false
	}

	if !testLiteralExpression(t, opExp.Right, right) {
		return false
	}

	return true
}

func testLiteralExpression(
	t *testing.T,
	exp ast.Expression,
	expected interface{},
) bool {
	switch v := expected.(type) {
	case int:
		return testIntegerLiteral(t, exp, int64(v))
	case int64:
		return testIntegerLiteral(t, exp, v)
	case string:
		return testIdentifier(t, exp, v)
	}
	t.Errorf("type of exp not handled. got=%T", exp)
	return false
}

func testIntegerLiteral(t *testing.T, il ast.Expression, value int64) bool {
	integ, ok := il.(*ast.IntegerLiteral)
	if !ok {
		t.Errorf("il not *ast.IntegerLiteral. got=%T", il)
		return false
	}

	if integ.Value != value {
		t.Errorf("integ.Value not %d. got=%d", value, integ.Value)
		return false
	}

	if integ.TokenLiteral() != fmt.Sprintf("%d", value) {
		t.Errorf("integ.TokenLiteral not %d. got=%s", value,
			integ.TokenLiteral())
		return false
	}

	return true
}

func testIdentifier(t *testing.T, exp ast.Expression, value string) bool {
	ident, ok := exp.(*ast.Identifier)
	if !ok {
		t.Errorf("exp not *ast.Identifier. got=%T", exp)
		return false
	}

	if ident.Value != value {
		t.Errorf("ident.Value not %s. got=%s", value, ident.Value)
		return false
	}

	if ident.TokenLiteral() != value {
		t.Errorf("ident.TokenLiteral not %s. got=%s", value,
			ident.TokenLiteral())
		return false
	}

	return true
}

func checkParserErrors(t *testing.T, p *Parser) {
	errors := p.Errors()
	if len(errors) == 0 {
		return
	}

	t.Errorf("parser has %d errors", len(errors))
	for _, msg := range errors {
		t.Errorf("parser error: %q", msg)
	}
	t.FailNow()
}