Implement null, true, and false

Fixes #28

parser/ast.go

@@ -14,6 +14,9 @@ type Node interface {
 type Ident struct {
 	Name     string
 	NameSpan Span
+
+	// Quoted is true if the identifier is quoted.
+	Quoted bool
 }
 
 func (id *Ident) Span() Span {

parser/parser.go

@@ -706,6 +706,7 @@ func (p *parser) ident() (*Ident, error) {
 	return &Ident{
 		Name:     tok.Value,
 		NameSpan: tok.Span,
+		Quoted:   tok.Kind == TokenQuotedIdentifier,
 	}, nil
 }
 

parser/parser_test.go

@@ -32,6 +32,19 @@ func TestParse(t *testing.T) {
 				},
 			},
 		},
+		{
+			name:  "OnlyQuotedTableName",
+			query: `["StormEvents"]`,
+			want: &TabularExpr{
+				Source: &TableRef{
+					Table: &Ident{
+						Name:     "StormEvents",
+						NameSpan: newSpan(0, 15),
+						Quoted:   true,
+					},
+				},
+			},
+		},
 		{
 			name:  "PipeCount",
 			query: "StormEvents | count",

pql.go

@@ -221,6 +221,12 @@ func quoteIdentifier(sb *strings.Builder, name string) {
 	sb.WriteString(`"`)
 }
 
+var builtinIdentifiers = map[string]string{
+	"true":  "TRUE",
+	"false": "FALSE",
+	"null":  "NULL",
+}
+
 var binaryOps = map[parser.TokenKind]string{
 	parser.TokenAnd:   "AND",
 	parser.TokenOr:    "OR",
@@ -248,7 +254,11 @@ func writeExpression(sb *strings.Builder, source string, x parser.Expr) error {
 
 	switch x := x.(type) {
 	case *parser.Ident:
-		quoteIdentifier(sb, x.Name)
+		if sql, ok := builtinIdentifiers[x.Name]; !x.Quoted && ok {
+			sb.WriteString(sql)
+		} else {
+			quoteIdentifier(sb, x.Name)
+		}
 	case *parser.BasicLit:
 		switch x.Kind {
 		case parser.TokenNumber:

testdata/Goldens/WhereTrue/input.pql

@@ -0,0 +1,2 @@
+StormEvents
+| where true

testdata/Goldens/WhereTrue/output.csv

@@ -0,0 +1,5 @@
+11032,ATLANTIC SOUTH,Waterspout,0
+11098,FLORIDA,Heavy Rain,0
+60913,FLORIDA,Tornado,6200000
+11503,GEORGIA,Thunderstorm Wind,2000
+13913,MISSISSIPPI,Thunderstorm Wind,20000

testdata/Goldens/WhereTrue/output.sql

@@ -0,0 +1 @@
+SELECT * FROM "StormEvents" WHERE TRUE;