cue/ast: add package
Change-Id: I587028ef8ce9e2e57eb75b8db5667b786dce9213
diff --git a/cue/ast/ast.go b/cue/ast/ast.go
new file mode 100644
index 0000000..cea67d9
--- /dev/null
+++ b/cue/ast/ast.go
@@ -0,0 +1,707 @@
+// Copyright 2018 The CUE Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package ast declares the types used to represent syntax trees for CUE
+// packages.
+package ast // import "cuelang.org/go/cue/ast"
+
+import (
+ "strconv"
+ "strings"
+
+ "cuelang.org/go/cue/token"
+)
+
+// ----------------------------------------------------------------------------
+// Interfaces
+//
+// There are two main classes of nodes: expressions, clauses, and declaration
+// nodes. The node names usually match the corresponding CUE spec production
+// names to which they correspond. The node fields correspond to the individual
+// parts of the respective productions.
+//
+// All nodes contain position information marking the beginning of the
+// corresponding source text segment; it is accessible via the Pos accessor
+// method. Nodes may contain additional position info for language constructs
+// where comments may be found between parts of the construct (typically any
+// larger, parenthesized subpart). That position information is needed to
+// properly position comments when printing the construct.
+
+// A Node represents any node in the abstract syntax tree.
+type Node interface {
+ Pos() token.Pos // position of first character belonging to the node
+ End() token.Pos // position of first character immediately after the node
+
+ // TODO: SetPos(p token.RelPos)
+
+ Comments() []*CommentGroup
+ AddComment(*CommentGroup)
+}
+
+// An Expr is implemented by all expression nodes.
+type Expr interface {
+ Node
+ exprNode()
+}
+
+func (*BadExpr) exprNode() {}
+func (*Ident) exprNode() {}
+func (*Ellipsis) exprNode() {}
+func (*BasicLit) exprNode() {}
+func (*Interpolation) exprNode() {}
+func (*StructLit) exprNode() {}
+func (*ListLit) exprNode() {}
+func (*LambdaExpr) exprNode() {}
+
+// func (*StructComprehension) exprNode() {}
+func (*ListComprehension) exprNode() {}
+func (*ParenExpr) exprNode() {}
+func (*SelectorExpr) exprNode() {}
+func (*IndexExpr) exprNode() {}
+func (*SliceExpr) exprNode() {}
+func (*CallExpr) exprNode() {}
+func (*UnaryExpr) exprNode() {}
+func (*BinaryExpr) exprNode() {}
+func (*BottomLit) exprNode() {}
+
+// A Decl node is implemented by all declarations.
+type Decl interface {
+ Node
+ declNode()
+}
+
+func (*Field) declNode() {}
+func (*ComprehensionDecl) declNode() {}
+func (*ImportDecl) declNode() {}
+func (*BadDecl) declNode() {}
+func (*EmitDecl) declNode() {}
+func (*Alias) declNode() {}
+
+// A Label is any prduction that can be used as a LHS label.
+type Label interface {
+ Node
+ labelName() (name string, isIdent bool)
+}
+
+func (n *Ident) labelName() (string, bool) {
+ return n.Name, true
+}
+
+func (n *BasicLit) labelName() (string, bool) {
+ switch n.Kind {
+ case token.STRING:
+ // Use strconv to only allow double-quoted, single-line strings.
+ if str, err := strconv.Unquote(n.Value); err == nil {
+ return str, true
+ }
+ case token.NULL, token.TRUE, token.FALSE:
+ return n.Value, true
+
+ // TODO: allow numbers to be fields?
+ }
+ return "", false
+}
+
+func (n *TemplateLabel) labelName() (string, bool) {
+ return n.Ident.Name, false
+}
+
+func (n *Interpolation) labelName() (string, bool) {
+ return "", false
+}
+func (n *ExprLabel) labelName() (string, bool) {
+ return "", false
+}
+
+// LabelName reports the name of a label, if known, and whether it is valid.
+func LabelName(x Label) (name string, ok bool) {
+ return x.labelName()
+}
+
+// As for now, a ExprLabel is not a label, as it can only use used in
+// struct comprehensions.
+
+// Clause nodes are part of comprehensions.
+type Clause interface {
+ Node
+ clauseNode()
+}
+
+func (x *ForClause) clauseNode() {}
+func (x *IfClause) clauseNode() {}
+func (x *Alias) clauseNode() {}
+
+// Comments
+
+type comments struct {
+ groups *[]*CommentGroup
+}
+
+func (c *comments) Comments() []*CommentGroup {
+ if c.groups == nil {
+ return []*CommentGroup{}
+ }
+ return *c.groups
+}
+
+// // AddComment adds the given comments to the fields.
+// // If line is true the comment is inserted at the preceding token.
+
+func (c *comments) AddComment(cg *CommentGroup) {
+ if cg == nil {
+ return
+ }
+ if c.groups == nil {
+ a := []*CommentGroup{cg}
+ c.groups = &a
+ return
+ }
+ *c.groups = append(*c.groups, cg)
+}
+
+// A Comment node represents a single //-style or /*-style comment.
+type Comment struct {
+ Slash token.Pos // position of "/" starting the comment
+ Text string // comment text (excluding '\n' for //-style comments)
+}
+
+func (g *Comment) Comments() []*CommentGroup { return nil }
+func (g *Comment) AddComment(*CommentGroup) {}
+
+func (c *Comment) Pos() token.Pos { return c.Slash }
+func (c *Comment) End() token.Pos { return c.Slash.Add(len(c.Text)) }
+
+// A CommentGroup represents a sequence of comments
+// with no other tokens and no empty lines between.
+type CommentGroup struct {
+ // TODO: remove and use the token position of the first commment.
+ Doc bool
+ Line bool // true if it is on the same line as the node's end pos.
+
+ // Position indicates where a comment should be attached if a node has
+ // multiple tokens. 0 means before the first token, 1 means before the
+ // second, etc. For instance, for a field, the positions are:
+ // <0> Label <1> ":" <2> Expr <3> "," <4>
+ Position int8
+ List []*Comment // len(List) > 0
+}
+
+func (g *CommentGroup) Pos() token.Pos { return g.List[0].Pos() }
+func (g *CommentGroup) End() token.Pos { return g.List[len(g.List)-1].End() }
+
+func (g *CommentGroup) Comments() []*CommentGroup { return nil }
+func (g *CommentGroup) AddComment(*CommentGroup) {}
+
+func isWhitespace(ch byte) bool { return ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r' }
+
+func stripTrailingWhitespace(s string) string {
+ i := len(s)
+ for i > 0 && isWhitespace(s[i-1]) {
+ i--
+ }
+ return s[0:i]
+}
+
+// Text returns the text of the comment.
+// Comment markers (//, /*, and */), the first space of a line comment, and
+// leading and trailing empty lines are removed. Multiple empty lines are
+// reduced to one, and trailing space on lines is trimmed. Unless the result
+// is empty, it is newline-terminated.
+func (g *CommentGroup) Text() string {
+ if g == nil {
+ return ""
+ }
+ comments := make([]string, len(g.List))
+ for i, c := range g.List {
+ comments[i] = c.Text
+ }
+
+ lines := make([]string, 0, 10) // most comments are less than 10 lines
+ for _, c := range comments {
+ // Remove comment markers.
+ // The parser has given us exactly the comment text.
+ switch c[1] {
+ case '/':
+ //-style comment (no newline at the end)
+ c = c[2:]
+ // strip first space - required for Example tests
+ if len(c) > 0 && c[0] == ' ' {
+ c = c[1:]
+ }
+ case '*':
+ /*-style comment */
+ c = c[2 : len(c)-2]
+ }
+
+ // Split on newlines.
+ cl := strings.Split(c, "\n")
+
+ // Walk lines, stripping trailing white space and adding to list.
+ for _, l := range cl {
+ lines = append(lines, stripTrailingWhitespace(l))
+ }
+ }
+
+ // Remove leading blank lines; convert runs of
+ // interior blank lines to a single blank line.
+ n := 0
+ for _, line := range lines {
+ if line != "" || n > 0 && lines[n-1] != "" {
+ lines[n] = line
+ n++
+ }
+ }
+ lines = lines[0:n]
+
+ // Add final "" entry to get trailing newline from Join.
+ if n > 0 && lines[n-1] != "" {
+ lines = append(lines, "")
+ }
+
+ return strings.Join(lines, "\n")
+}
+
+// A Field represents a field declaration in a struct.
+type Field struct {
+ comments
+ Label Label // must have at least one element.
+
+ // No colon: Value must be an StructLit with one field or a
+ // LambdaExpr.
+ Colon token.Pos
+ Value Expr // the value associated with this field.
+}
+
+func (d *Field) Pos() token.Pos { return d.Label.Pos() }
+func (d *Field) End() token.Pos { return d.Value.End() }
+
+// An Alias binds another field to the alias name in the current struct.
+type Alias struct {
+ comments
+ Ident *Ident // field name, always an Ident
+ Equal token.Pos // position of "="
+ Expr Expr // An Ident or SelectorExpr
+}
+
+func (a *Alias) Pos() token.Pos { return a.Ident.Pos() }
+func (a *Alias) End() token.Pos { return a.Expr.End() }
+
+// A ComprehensionDecl node represents a field comprehension.
+type ComprehensionDecl struct {
+ comments
+ Field *Field
+ Select token.Pos
+ Clauses []Clause
+}
+
+func (x *ComprehensionDecl) Pos() token.Pos { return x.Field.Pos() }
+func (x *ComprehensionDecl) End() token.Pos {
+ if len(x.Clauses) > 0 {
+ return x.Clauses[len(x.Clauses)-1].End()
+ }
+ return x.Select
+}
+
+// ----------------------------------------------------------------------------
+// Expressions and types
+//
+// An expression is represented by a tree consisting of one
+// or more of the following concrete expression nodes.
+
+// A LambdaExpr defines a function expression.
+//
+// Lambdas are only used internally under controlled conditions. Although
+// the implementation of lambdas is fully functional, enabling them will
+// cause the language to be Turing-complete (if not otherwise limited).
+// Also, lambdas would provide yet another way to create structure, and one
+// that is known to not work well for declarative configuration languages.
+type LambdaExpr struct {
+ comments
+ Lparen token.Pos // position of "("
+ Params []*Field // parameters with possible initializers
+ Rparen token.Pos // position of ")"
+ Expr Expr
+}
+
+func (t *LambdaExpr) Pos() token.Pos { return t.Lparen }
+func (t *LambdaExpr) End() token.Pos { return t.Rparen }
+
+// A BadExpr node is a placeholder for expressions containing
+// syntax errors for which no correct expression nodes can be
+// created. This is different from an ErrorExpr which represents
+// an explicitly marked error in the source.
+type BadExpr struct {
+ comments
+ From, To token.Pos // position range of bad expression
+}
+
+// A BottomLit indicates an error.
+type BottomLit struct {
+ comments
+ Bottom token.Pos
+}
+
+// An Ident node represents an left-hand side identifier.
+type Ident struct {
+ comments
+ NamePos token.Pos // identifier position
+
+ // This LHS path element may be an identifier. Possible forms:
+ // foo: a normal identifier
+ // "foo": JSON compatible
+ // <foo>: a template shorthand
+ Name string
+
+ Scope Node // scope in which node was found or nil if referring directly
+ Node Node
+}
+
+// A TemplateLabel represents a field template declaration in a struct.
+type TemplateLabel struct {
+ comments
+ Langle token.Pos
+ Ident *Ident
+ Rangle token.Pos
+}
+
+// An ExprLabel is an expression to create a label in struct comprehensions.
+type ExprLabel struct {
+ comments
+ Lbrack token.Pos
+ Label Expr
+ Rbrack token.Pos
+}
+
+// An Ellipsis node stands for the "..." type in a
+// parameter list or the "..." length in an array type.
+type Ellipsis struct {
+ comments
+ Ellipsis token.Pos // position of "..."
+ Elt Expr // ellipsis element type (parameter lists only); or nil
+}
+
+// A BasicLit node represents a literal of basic type.
+type BasicLit struct {
+ comments
+ ValuePos token.Pos // literal position
+ Kind token.Token // INT, FLOAT, DURATION, or STRING
+ Value string // literal string; e.g. 42, 0x7f, 3.14, 1_234_567, 1e-9, 2.4i, 'a', '\x7f', "foo", or '\m\n\o'
+}
+
+// A Interpolation node represents a string or bytes interpolation.
+type Interpolation struct { // TODO: rename to TemplateLit
+ comments
+ Elts []Expr // interleaving of strings and expressions.
+}
+
+// A StructLit node represents a literal struct.
+type StructLit struct {
+ comments
+ Lbrace token.Pos // position of "{"
+ Elts []Decl // list of elements; or nil
+ Rbrace token.Pos // position of "}"
+}
+
+// A ListLit node represents a literal list.
+type ListLit struct {
+ comments
+ Lbrack token.Pos // position of "["
+ Elts []Expr // list of composite elements; or nil
+ Ellipsis token.Pos // open list if set
+ Type Expr // type for the remaining elements
+ Rbrack token.Pos // position of "]"
+}
+
+// A ListComprehension node represents as list comprehension.
+type ListComprehension struct {
+ comments
+ Lbrack token.Pos // position of "["
+ Expr Expr
+ Clauses []Clause // Feed or Guard (TODO let)
+ Rbrack token.Pos // position of "]"
+}
+
+// A ForClause node represents a for clause in a comprehension.
+type ForClause struct {
+ comments
+ For token.Pos
+ Key *Ident // allow pattern matching?
+ Colon token.Pos
+ Value *Ident // allow pattern matching?
+ In token.Pos
+ Source Expr
+}
+
+// A IfClause node represents an if guard clause in a comprehension.
+type IfClause struct {
+ comments
+ If token.Pos
+ Condition Expr
+}
+
+// A ParenExpr node represents a parenthesized expression.
+type ParenExpr struct {
+ comments
+ Lparen token.Pos // position of "("
+ X Expr // parenthesized expression
+ Rparen token.Pos // position of ")"
+}
+
+// A SelectorExpr node represents an expression followed by a selector.
+type SelectorExpr struct {
+ comments
+ X Expr // expression
+ Sel *Ident // field selector
+}
+
+// An IndexExpr node represents an expression followed by an index.
+type IndexExpr struct {
+ comments
+ X Expr // expression
+ Lbrack token.Pos // position of "["
+ Index Expr // index expression
+ Rbrack token.Pos // position of "]"
+}
+
+// An SliceExpr node represents an expression followed by slice indices.
+type SliceExpr struct {
+ comments
+ X Expr // expression
+ Lbrack token.Pos // position of "["
+ Low Expr // begin of slice range; or nil
+ High Expr // end of slice range; or nil
+ Rbrack token.Pos // position of "]"
+}
+
+// A CallExpr node represents an expression followed by an argument list.
+type CallExpr struct {
+ comments
+ Fun Expr // function expression
+ Lparen token.Pos // position of "("
+ Args []Expr // function arguments; or nil
+ Rparen token.Pos // position of ")"
+}
+
+// A UnaryExpr node represents a unary expression.
+type UnaryExpr struct {
+ comments
+ OpPos token.Pos // position of Op
+ Op token.Token // operator
+ X Expr // operand
+}
+
+// A BinaryExpr node represents a binary expression.
+type BinaryExpr struct {
+ comments
+ X Expr // left operand
+ OpPos token.Pos // position of Op
+ Op token.Token // operator
+ Y Expr // right operand
+}
+
+// token.Pos and End implementations for expression/type nodes.
+
+func (x *BadExpr) Pos() token.Pos { return x.From }
+func (x *Ident) Pos() token.Pos { return x.NamePos }
+func (x *TemplateLabel) Pos() token.Pos { return x.Langle }
+func (x *ExprLabel) Pos() token.Pos { return x.Lbrack }
+func (x *Ellipsis) Pos() token.Pos { return x.Ellipsis }
+func (x *BasicLit) Pos() token.Pos { return x.ValuePos }
+func (x *Interpolation) Pos() token.Pos { return x.Elts[0].Pos() }
+func (x *StructLit) Pos() token.Pos {
+ if x.Lbrace == token.NoPos && len(x.Elts) > 0 {
+ return x.Elts[0].Pos()
+ }
+ return x.Lbrace
+}
+
+func (x *ListLit) Pos() token.Pos { return x.Lbrack }
+func (x *ListComprehension) Pos() token.Pos { return x.Lbrack }
+func (x *ForClause) Pos() token.Pos { return x.For }
+func (x *IfClause) Pos() token.Pos { return x.If }
+func (x *ParenExpr) Pos() token.Pos { return x.Lparen }
+func (x *SelectorExpr) Pos() token.Pos { return x.X.Pos() }
+func (x *IndexExpr) Pos() token.Pos { return x.X.Pos() }
+func (x *SliceExpr) Pos() token.Pos { return x.X.Pos() }
+func (x *CallExpr) Pos() token.Pos { return x.Fun.Pos() }
+func (x *UnaryExpr) Pos() token.Pos { return x.OpPos }
+func (x *BinaryExpr) Pos() token.Pos { return x.X.Pos() }
+func (x *BottomLit) Pos() token.Pos { return x.Bottom }
+
+func (x *BadExpr) End() token.Pos { return x.To }
+func (x *Ident) End() token.Pos {
+ return x.NamePos.Add(len(x.Name))
+}
+func (x *TemplateLabel) End() token.Pos { return x.Rangle }
+func (x *ExprLabel) End() token.Pos { return x.Rbrack }
+func (x *Ellipsis) End() token.Pos {
+ if x.Elt != nil {
+ return x.Elt.End()
+ }
+ return x.Ellipsis + 3 // len("...")
+}
+func (x *BasicLit) End() token.Pos { return token.Pos(int(x.ValuePos) + len(x.Value)) }
+func (x *Interpolation) End() token.Pos { return x.Elts[len(x.Elts)-1].Pos() }
+func (x *StructLit) End() token.Pos {
+ if x.Rbrace == token.NoPos && len(x.Elts) > 0 {
+ return x.Elts[len(x.Elts)-1].Pos()
+ }
+ return x.Rbrace.Add(1)
+}
+func (x *ListLit) End() token.Pos { return x.Rbrack.Add(1) }
+func (x *ListComprehension) End() token.Pos { return x.Rbrack }
+func (x *ForClause) End() token.Pos { return x.Source.End() }
+func (x *IfClause) End() token.Pos { return x.Condition.End() }
+func (x *ParenExpr) End() token.Pos { return x.Rparen.Add(1) }
+func (x *SelectorExpr) End() token.Pos { return x.Sel.End() }
+func (x *IndexExpr) End() token.Pos { return x.Rbrack.Add(1) }
+func (x *SliceExpr) End() token.Pos { return x.Rbrack.Add(1) }
+func (x *CallExpr) End() token.Pos { return x.Rparen.Add(1) }
+func (x *UnaryExpr) End() token.Pos { return x.X.End() }
+func (x *BinaryExpr) End() token.Pos { return x.Y.End() }
+func (x *BottomLit) End() token.Pos { return x.Bottom.Add(1) }
+
+// ----------------------------------------------------------------------------
+// Convenience functions for Idents
+
+// NewIdent creates a new Ident without position.
+// Useful for ASTs generated by code other than the Go
+func NewIdent(name string) *Ident {
+ return &Ident{comments{}, token.NoPos, name, nil, nil}
+}
+
+func (id *Ident) String() string {
+ if id != nil {
+ return id.Name
+ }
+ return "<nil>"
+}
+
+// ----------------------------------------------------------------------------
+// Declarations
+
+// An ImportSpec node represents a single package import.
+type ImportSpec struct {
+ comments
+ Name *Ident // local package name (including "."); or nil
+ Path *BasicLit // import path
+ EndPos token.Pos // end of spec (overrides Path.Pos if nonzero)
+}
+
+// Pos and End implementations for spec nodes.
+
+func (s *ImportSpec) Pos() token.Pos {
+ if s.Name != nil {
+ return s.Name.Pos()
+ }
+ return s.Path.Pos()
+}
+
+// func (s *AliasSpec) Pos() token.Pos { return s.Name.Pos() }
+// func (s *ValueSpec) Pos() token.Pos { return s.Names[0].Pos() }
+// func (s *TypeSpec) Pos() token.Pos { return s.Name.Pos() }
+
+func (s *ImportSpec) End() token.Pos {
+ if s.EndPos != 0 {
+ return s.EndPos
+ }
+ return s.Path.End()
+}
+
+// specNode() ensures that only spec nodes can be assigned to a Spec.
+func (*ImportSpec) specNode() {}
+
+// A declaration is represented by one of the following declaration nodes.
+type (
+ // A BadDecl node is a placeholder for declarations containing
+ // syntax errors for which no correct declaration nodes can be
+ // created.
+ BadDecl struct {
+ comments
+ From, To token.Pos // position range of bad declaration
+ }
+
+ // A ImportDecl node represents a series of import declarations. A valid
+ // Lparen position (Lparen.Line > 0) indicates a parenthesized declaration.
+ ImportDecl struct {
+ comments
+ Import token.Pos
+ Lparen token.Pos // position of '(', if any
+ Specs []*ImportSpec
+ Rparen token.Pos // position of ')', if any
+ }
+
+ // An EmitDecl node represents a single expression used as a declaration.
+ // The expressions in this declaration is what will be emitted as
+ // configuration output.
+ //
+ // An EmitDecl may only appear at the top level.
+ EmitDecl struct {
+ comments
+ Expr Expr
+ }
+)
+
+// Pos and End implementations for declaration nodes.
+
+func (d *BadDecl) Pos() token.Pos { return d.From }
+func (d *ImportDecl) Pos() token.Pos { return d.Import }
+func (d *EmitDecl) Pos() token.Pos { return d.Expr.Pos() }
+
+func (d *BadDecl) End() token.Pos { return d.To }
+func (d *ImportDecl) End() token.Pos {
+ if d.Rparen.IsValid() {
+ return d.Rparen.Add(1)
+ }
+ return d.Specs[0].End()
+}
+func (d *EmitDecl) End() token.Pos { return d.Expr.End() }
+
+// ----------------------------------------------------------------------------
+// Files and packages
+
+// A File node represents a Go source file.
+//
+// The Comments list contains all comments in the source file in order of
+// appearance, including the comments that are pointed to from other nodes
+// via Doc and Comment fields.
+type File struct {
+ Filename string
+ comments
+ Package token.Pos // position of "package" pseudo-keyword
+ Name *Ident // package names
+ // TODO: Change Expr to Decl?
+ Imports []*ImportSpec // imports in this file
+ Decls []Decl // top-level declarations; or nil
+ Unresolved []*Ident // unresolved identifiers in this file
+}
+
+func (f *File) Pos() token.Pos {
+ if f.Package != token.NoPos {
+ return f.Package
+ }
+ if len(f.Decls) > 0 {
+ return f.Decls[0].Pos()
+ }
+ return token.NoPos
+}
+func (f *File) End() token.Pos {
+ if n := len(f.Decls); n > 0 {
+ return f.Decls[n-1].End()
+ }
+ if f.Name != nil {
+ return f.Name.End()
+ }
+ return token.NoPos
+}
diff --git a/cue/ast/ast_test.go b/cue/ast/ast_test.go
new file mode 100644
index 0000000..4272ffe
--- /dev/null
+++ b/cue/ast/ast_test.go
@@ -0,0 +1,60 @@
+// Copyright 2018 The CUE Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ast
+
+import (
+ "testing"
+)
+
+func TestCommentText(t *testing.T) {
+ testCases := []struct {
+ list []string
+ text string
+ }{
+ {[]string{"//"}, ""},
+ {[]string{"// "}, ""},
+ {[]string{"//", "//", "// "}, ""},
+ {[]string{"// foo "}, "foo\n"},
+ {[]string{"//", "//", "// foo"}, "foo\n"},
+ {[]string{"// foo bar "}, "foo bar\n"},
+ {[]string{"// foo", "// bar"}, "foo\nbar\n"},
+ {[]string{"// foo", "//", "//", "//", "// bar"}, "foo\n\nbar\n"},
+ {[]string{"// foo", "/* bar */"}, "foo\n bar\n"},
+ {[]string{"//", "//", "//", "// foo", "//", "//", "//"}, "foo\n"},
+
+ {[]string{"/**/"}, ""},
+ {[]string{"/* */"}, ""},
+ {[]string{"/**/", "/**/", "/* */"}, ""},
+ {[]string{"/* Foo */"}, " Foo\n"},
+ {[]string{"/* Foo Bar */"}, " Foo Bar\n"},
+ {[]string{"/* Foo*/", "/* Bar*/"}, " Foo\n Bar\n"},
+ {[]string{"/* Foo*/", "/**/", "/**/", "/**/", "// Bar"}, " Foo\n\nBar\n"},
+ {[]string{"/* Foo*/", "/*\n*/", "//", "/*\n*/", "// Bar"}, " Foo\n\nBar\n"},
+ {[]string{"/* Foo*/", "// Bar"}, " Foo\nBar\n"},
+ {[]string{"/* Foo\n Bar*/"}, " Foo\n Bar\n"},
+ }
+
+ for i, c := range testCases {
+ list := make([]*Comment, len(c.list))
+ for i, s := range c.list {
+ list[i] = &Comment{Text: s}
+ }
+
+ text := (&CommentGroup{List: list}).Text()
+ if text != c.text {
+ t.Errorf("case %d: got %q; expected %q", i, text, c.text)
+ }
+ }
+}
diff --git a/cue/ast/walk.go b/cue/ast/walk.go
new file mode 100644
index 0000000..be492e3
--- /dev/null
+++ b/cue/ast/walk.go
@@ -0,0 +1,287 @@
+// Copyright 2018 The CUE Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ast
+
+import (
+ "fmt"
+
+ "cuelang.org/go/cue/token"
+)
+
+// Walk traverses an AST in depth-first order: It starts by calling f(node);
+// node must not be nil. If before returns true, Walk invokes f recursively for
+// each of the non-nil children of node, followed by a call of after. Both
+// functions may be nil. If before is nil, it is assumed to always return true.
+//
+func Walk(node Node, before func(Node) bool, after func(Node)) {
+ walk(&inspector{before: before, after: after}, node)
+}
+
+// A visitor's before method is invoked for each node encountered by Walk.
+// If the result visitor w is not nil, Walk visits each of the children
+// of node with the visitor w, followed by a call of w.After.
+type visitor interface {
+ Before(node Node) (w visitor)
+ After(node Node)
+}
+
+// Helper functions for common node lists. They may be empty.
+
+func walkIdentList(v visitor, list []*Ident) {
+ for _, x := range list {
+ walk(v, x)
+ }
+}
+
+func walkExprList(v visitor, list []Expr) {
+ for _, x := range list {
+ walk(v, x)
+ }
+}
+
+func walkDeclList(v visitor, list []Decl) {
+ for _, x := range list {
+ walk(v, x)
+ }
+}
+
+// walk traverses an AST in depth-first order: It starts by calling
+// v.Visit(node); node must not be nil. If the visitor w returned by
+// v.Visit(node) is not nil, walk is invoked recursively with visitor
+// w for each of the non-nil children of node, followed by a call of
+// w.Visit(nil).
+//
+func walk(v visitor, node Node) {
+ if v = v.Before(node); v == nil {
+ return
+ }
+
+ // TODO: record the comment groups and interleave with the values like for
+ // parsing and printing?
+ for _, c := range node.Comments() {
+ walk(v, c)
+ }
+
+ // walk children
+ // (the order of the cases matches the order
+ // of the corresponding node types in go)
+ switch n := node.(type) {
+ // Comments and fields
+ case *Comment:
+ // nothing to do
+
+ case *CommentGroup:
+ for _, c := range n.List {
+ walk(v, c)
+ }
+
+ case *Field:
+ walk(v, n.Label)
+ if n.Value != nil {
+ walk(v, n.Value)
+ }
+
+ case *LambdaExpr:
+ for _, p := range n.Params {
+ walk(v, p)
+ }
+ walk(v, n.Expr)
+
+ case *StructLit:
+ for _, f := range n.Elts {
+ walk(v, f)
+ }
+
+ // Expressions
+ case *BottomLit, *BadExpr, *Ident, *BasicLit:
+ // nothing to do
+
+ case *ExprLabel:
+ walk(v, n.Label)
+
+ case *TemplateLabel:
+ walk(v, n.Ident)
+
+ case *Interpolation:
+ for _, e := range n.Elts {
+ walk(v, e)
+ }
+
+ case *Ellipsis:
+ if n.Elt != nil {
+ walk(v, n.Elt)
+ }
+
+ case *ListLit:
+ walkExprList(v, n.Elts)
+ if n.Type != nil {
+ walk(v, n.Type)
+ }
+
+ case *ParenExpr:
+ walk(v, n.X)
+
+ case *SelectorExpr:
+ walk(v, n.X)
+ walk(v, n.Sel)
+
+ case *IndexExpr:
+ walk(v, n.X)
+ walk(v, n.Index)
+
+ case *SliceExpr:
+ walk(v, n.X)
+ if n.Low != nil {
+ walk(v, n.Low)
+ }
+ if n.High != nil {
+ walk(v, n.High)
+ }
+
+ case *CallExpr:
+ walk(v, n.Fun)
+ walkExprList(v, n.Args)
+
+ case *UnaryExpr:
+ walk(v, n.X)
+
+ case *BinaryExpr:
+ walk(v, n.X)
+ walk(v, n.Y)
+
+ // Declarations
+ case *ImportSpec:
+ if n.Name != nil {
+ walk(v, n.Name)
+ }
+ walk(v, n.Path)
+
+ case *BadDecl:
+ // nothing to do
+
+ case *ImportDecl:
+ for _, s := range n.Specs {
+ walk(v, s)
+ }
+
+ case *EmitDecl:
+ walk(v, n.Expr)
+
+ case *Alias:
+ walk(v, n.Ident)
+ walk(v, n.Expr)
+
+ case *ComprehensionDecl:
+ walk(v, n.Field)
+ for _, c := range n.Clauses {
+ walk(v, c)
+ }
+
+ // Files and packages
+ case *File:
+ if n.Name != nil {
+ walk(v, n.Name)
+ }
+ walkDeclList(v, n.Decls)
+ // don't walk n.Comments - they have been
+ // visited already through the individual
+ // nodes
+
+ case *ListComprehension:
+ walk(v, n.Expr)
+ for _, c := range n.Clauses {
+ walk(v, c)
+ }
+
+ case *ForClause:
+ if n.Key != nil {
+ walk(v, n.Key)
+ }
+ walk(v, n.Value)
+ walk(v, n.Source)
+
+ case *IfClause:
+ walk(v, n.Condition)
+
+ default:
+ panic(fmt.Sprintf("Walk: unexpected node type %T", n))
+ }
+
+ v.After(node)
+}
+
+type inspector struct {
+ before func(Node) bool
+ after func(Node)
+
+ commentStack []commentFrame
+ current commentFrame
+}
+
+type commentFrame struct {
+ cg []*CommentGroup
+ pos int8
+}
+
+func (f *inspector) Before(node Node) visitor {
+ if f.before == nil || f.before(node) {
+ f.commentStack = append(f.commentStack, f.current)
+ f.current = commentFrame{cg: node.Comments()}
+ f.visitComments(f.current.pos)
+ return f
+ }
+ return nil
+}
+
+func (f *inspector) After(node Node) {
+ f.visitComments(127)
+ p := len(f.commentStack) - 1
+ f.current = f.commentStack[p]
+ f.commentStack = f.commentStack[:p]
+ f.current.pos++
+ if f.after != nil {
+ f.after(node)
+ }
+}
+
+func (f *inspector) Token(t token.Token) {
+ f.current.pos++
+}
+
+func (f *inspector) setPos(i int8) {
+ f.current.pos = i
+}
+
+func (f *inspector) visitComments(pos int8) {
+ c := &f.current
+ for ; len(c.cg) > 0; c.cg = c.cg[1:] {
+ cg := c.cg[0]
+ if cg.Position == pos {
+ continue
+ }
+ if f.before == nil || f.before(cg) {
+ for _, c := range cg.List {
+ if f.before == nil || f.before(c) {
+ if f.after != nil {
+ f.after(c)
+ }
+ }
+ }
+ if f.after != nil {
+ f.after(cg)
+ }
+ }
+ }
+}
