add an initial css lexer+parser+printer (#20)

internal/css_ast/css_ast.go

@@ -0,0 +1,111 @@
+package css_ast
+
+import (
+	"github.com/evanw/esbuild/internal/css_lexer"
+	"github.com/evanw/esbuild/internal/logger"
+)
+
+type AST struct {
+	Rules []R
+}
+
+// This interface is never called. Its purpose is to encode a variant type in
+// Go's type system.
+type R interface {
+	isRule()
+}
+
+type RAtImport struct {
+	PathText  string
+	PathRange logger.Range
+}
+
+type RKnownAt struct {
+	Name    css_lexer.Token
+	Prelude []css_lexer.Token
+	Rules   []R
+}
+
+type RUnknownAt struct {
+	Name    css_lexer.Token
+	Prelude []css_lexer.Token
+	Block   []css_lexer.Token
+}
+
+type RSelector struct {
+	Selectors []ComplexSelector
+	Rules     []R
+}
+
+type RQualified struct {
+	Prelude []css_lexer.Token
+	Rules   []R
+}
+
+type RDeclaration struct {
+	Key       css_lexer.Token
+	Value     []css_lexer.Token
+	Important bool
+}
+
+type RBadDeclaration struct {
+	Tokens []css_lexer.Token
+}
+
+func (*RAtImport) isRule()       {}
+func (*RKnownAt) isRule()        {}
+func (*RUnknownAt) isRule()      {}
+func (*RSelector) isRule()       {}
+func (*RQualified) isRule()      {}
+func (*RDeclaration) isRule()    {}
+func (*RBadDeclaration) isRule() {}
+
+type ComplexSelector struct {
+	Selectors []CompoundSelector
+}
+
+type CompoundSelector struct {
+	Combinator           string // Optional, may be ""
+	TypeSelector         *NamespacedName
+	SubclassSelectors    []SS
+	PseudoClassSelectors []SSPseudoClass // If present, these follow a ":" character
+}
+
+type NamespacedName struct {
+	// If present, this is an identifier or "*" or "" and is followed by a "|" character
+	NamespacePrefix *string
+
+	// This is an identifier or "*" or "&"
+	Name string
+}
+
+// This interface is never called. Its purpose is to encode a variant type in
+// Go's type system.
+type SS interface {
+	isSubclassSelector()
+}
+
+type SSHash struct {
+	Name string
+}
+
+type SSClass struct {
+	Name string
+}
+
+type SSAttribute struct {
+	NamespacedName  NamespacedName
+	MatcherOp       string
+	MatcherValue    string
+	MatcherModifier byte
+}
+
+type SSPseudoClass struct {
+	Name string
+	Args []css_lexer.Token
+}
+
+func (*SSHash) isSubclassSelector()        {}
+func (*SSClass) isSubclassSelector()       {}
+func (*SSAttribute) isSubclassSelector()   {}
+func (*SSPseudoClass) isSubclassSelector() {}