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Diffstat (limited to 'syntax/syntax.go')
| -rw-r--r-- | syntax/syntax.go | 529 |
1 files changed, 529 insertions, 0 deletions
diff --git a/syntax/syntax.go b/syntax/syntax.go new file mode 100644 index 0000000..20b28bb --- /dev/null +++ b/syntax/syntax.go @@ -0,0 +1,529 @@ +// Copyright 2017 The Bazel Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Package syntax provides a Starlark parser and abstract syntax tree. +package syntax // import "go.starlark.net/syntax" + +// A Node is a node in a Starlark syntax tree. +type Node interface { + // Span returns the start and end position of the expression. + Span() (start, end Position) + + // Comments returns the comments associated with this node. + // It returns nil if RetainComments was not specified during parsing, + // or if AllocComments was not called. + Comments() *Comments + + // AllocComments allocates a new Comments node if there was none. + // This makes possible to add new comments using Comments() method. + AllocComments() +} + +// A Comment represents a single # comment. +type Comment struct { + Start Position + Text string // without trailing newline +} + +// Comments collects the comments associated with an expression. +type Comments struct { + Before []Comment // whole-line comments before this expression + Suffix []Comment // end-of-line comments after this expression (up to 1) + + // For top-level expressions only, After lists whole-line + // comments following the expression. + After []Comment +} + +// A commentsRef is a possibly-nil reference to a set of comments. +// A commentsRef is embedded in each type of syntax node, +// and provides its Comments and AllocComments methods. +type commentsRef struct{ ref *Comments } + +// Comments returns the comments associated with a syntax node, +// or nil if AllocComments has not yet been called. +func (cr commentsRef) Comments() *Comments { return cr.ref } + +// AllocComments enables comments to be associated with a syntax node. +func (cr *commentsRef) AllocComments() { + if cr.ref == nil { + cr.ref = new(Comments) + } +} + +// Start returns the start position of the expression. +func Start(n Node) Position { + start, _ := n.Span() + return start +} + +// End returns the end position of the expression. +func End(n Node) Position { + _, end := n.Span() + return end +} + +// A File represents a Starlark file. +type File struct { + commentsRef + Path string + Stmts []Stmt + + Module interface{} // a *resolve.Module, set by resolver +} + +func (x *File) Span() (start, end Position) { + if len(x.Stmts) == 0 { + return + } + start, _ = x.Stmts[0].Span() + _, end = x.Stmts[len(x.Stmts)-1].Span() + return start, end +} + +// A Stmt is a Starlark statement. +type Stmt interface { + Node + stmt() +} + +func (*AssignStmt) stmt() {} +func (*BranchStmt) stmt() {} +func (*DefStmt) stmt() {} +func (*ExprStmt) stmt() {} +func (*ForStmt) stmt() {} +func (*WhileStmt) stmt() {} +func (*IfStmt) stmt() {} +func (*LoadStmt) stmt() {} +func (*ReturnStmt) stmt() {} + +// An AssignStmt represents an assignment: +// x = 0 +// x, y = y, x +// x += 1 +type AssignStmt struct { + commentsRef + OpPos Position + Op Token // = EQ | {PLUS,MINUS,STAR,PERCENT}_EQ + LHS Expr + RHS Expr +} + +func (x *AssignStmt) Span() (start, end Position) { + start, _ = x.LHS.Span() + _, end = x.RHS.Span() + return +} + +// A DefStmt represents a function definition. +type DefStmt struct { + commentsRef + Def Position + Name *Ident + Params []Expr // param = ident | ident=expr | * | *ident | **ident + Body []Stmt + + Function interface{} // a *resolve.Function, set by resolver +} + +func (x *DefStmt) Span() (start, end Position) { + _, end = x.Body[len(x.Body)-1].Span() + return x.Def, end +} + +// An ExprStmt is an expression evaluated for side effects. +type ExprStmt struct { + commentsRef + X Expr +} + +func (x *ExprStmt) Span() (start, end Position) { + return x.X.Span() +} + +// An IfStmt is a conditional: If Cond: True; else: False. +// 'elseif' is desugared into a chain of IfStmts. +type IfStmt struct { + commentsRef + If Position // IF or ELIF + Cond Expr + True []Stmt + ElsePos Position // ELSE or ELIF + False []Stmt // optional +} + +func (x *IfStmt) Span() (start, end Position) { + body := x.False + if body == nil { + body = x.True + } + _, end = body[len(body)-1].Span() + return x.If, end +} + +// A LoadStmt loads another module and binds names from it: +// load(Module, "x", y="foo"). +// +// The AST is slightly unfaithful to the concrete syntax here because +// Starlark's load statement, so that it can be implemented in Python, +// binds some names (like y above) with an identifier and some (like x) +// without. For consistency we create fake identifiers for all the +// strings. +type LoadStmt struct { + commentsRef + Load Position + Module *Literal // a string + From []*Ident // name defined in loading module + To []*Ident // name in loaded module + Rparen Position +} + +func (x *LoadStmt) Span() (start, end Position) { + return x.Load, x.Rparen +} + +// ModuleName returns the name of the module loaded by this statement. +func (x *LoadStmt) ModuleName() string { return x.Module.Value.(string) } + +// A BranchStmt changes the flow of control: break, continue, pass. +type BranchStmt struct { + commentsRef + Token Token // = BREAK | CONTINUE | PASS + TokenPos Position +} + +func (x *BranchStmt) Span() (start, end Position) { + return x.TokenPos, x.TokenPos.add(x.Token.String()) +} + +// A ReturnStmt returns from a function. +type ReturnStmt struct { + commentsRef + Return Position + Result Expr // may be nil +} + +func (x *ReturnStmt) Span() (start, end Position) { + if x.Result == nil { + return x.Return, x.Return.add("return") + } + _, end = x.Result.Span() + return x.Return, end +} + +// An Expr is a Starlark expression. +type Expr interface { + Node + expr() +} + +func (*BinaryExpr) expr() {} +func (*CallExpr) expr() {} +func (*Comprehension) expr() {} +func (*CondExpr) expr() {} +func (*DictEntry) expr() {} +func (*DictExpr) expr() {} +func (*DotExpr) expr() {} +func (*Ident) expr() {} +func (*IndexExpr) expr() {} +func (*LambdaExpr) expr() {} +func (*ListExpr) expr() {} +func (*Literal) expr() {} +func (*ParenExpr) expr() {} +func (*SliceExpr) expr() {} +func (*TupleExpr) expr() {} +func (*UnaryExpr) expr() {} + +// An Ident represents an identifier. +type Ident struct { + commentsRef + NamePos Position + Name string + + Binding interface{} // a *resolver.Binding, set by resolver +} + +func (x *Ident) Span() (start, end Position) { + return x.NamePos, x.NamePos.add(x.Name) +} + +// A Literal represents a literal string or number. +type Literal struct { + commentsRef + Token Token // = STRING | BYTES | INT | FLOAT + TokenPos Position + Raw string // uninterpreted text + Value interface{} // = string | int64 | *big.Int | float64 +} + +func (x *Literal) Span() (start, end Position) { + return x.TokenPos, x.TokenPos.add(x.Raw) +} + +// A ParenExpr represents a parenthesized expression: (X). +type ParenExpr struct { + commentsRef + Lparen Position + X Expr + Rparen Position +} + +func (x *ParenExpr) Span() (start, end Position) { + return x.Lparen, x.Rparen.add(")") +} + +// A CallExpr represents a function call expression: Fn(Args). +type CallExpr struct { + commentsRef + Fn Expr + Lparen Position + Args []Expr // arg = expr | ident=expr | *expr | **expr + Rparen Position +} + +func (x *CallExpr) Span() (start, end Position) { + start, _ = x.Fn.Span() + return start, x.Rparen.add(")") +} + +// A DotExpr represents a field or method selector: X.Name. +type DotExpr struct { + commentsRef + X Expr + Dot Position + NamePos Position + Name *Ident +} + +func (x *DotExpr) Span() (start, end Position) { + start, _ = x.X.Span() + _, end = x.Name.Span() + return +} + +// A Comprehension represents a list or dict comprehension: +// [Body for ... if ...] or {Body for ... if ...} +type Comprehension struct { + commentsRef + Curly bool // {x:y for ...} or {x for ...}, not [x for ...] + Lbrack Position + Body Expr + Clauses []Node // = *ForClause | *IfClause + Rbrack Position +} + +func (x *Comprehension) Span() (start, end Position) { + return x.Lbrack, x.Rbrack.add("]") +} + +// A ForStmt represents a loop: for Vars in X: Body. +type ForStmt struct { + commentsRef + For Position + Vars Expr // name, or tuple of names + X Expr + Body []Stmt +} + +func (x *ForStmt) Span() (start, end Position) { + _, end = x.Body[len(x.Body)-1].Span() + return x.For, end +} + +// A WhileStmt represents a while loop: while X: Body. +type WhileStmt struct { + commentsRef + While Position + Cond Expr + Body []Stmt +} + +func (x *WhileStmt) Span() (start, end Position) { + _, end = x.Body[len(x.Body)-1].Span() + return x.While, end +} + +// A ForClause represents a for clause in a list comprehension: for Vars in X. +type ForClause struct { + commentsRef + For Position + Vars Expr // name, or tuple of names + In Position + X Expr +} + +func (x *ForClause) Span() (start, end Position) { + _, end = x.X.Span() + return x.For, end +} + +// An IfClause represents an if clause in a list comprehension: if Cond. +type IfClause struct { + commentsRef + If Position + Cond Expr +} + +func (x *IfClause) Span() (start, end Position) { + _, end = x.Cond.Span() + return x.If, end +} + +// A DictExpr represents a dictionary literal: { List }. +type DictExpr struct { + commentsRef + Lbrace Position + List []Expr // all *DictEntrys + Rbrace Position +} + +func (x *DictExpr) Span() (start, end Position) { + return x.Lbrace, x.Rbrace.add("}") +} + +// A DictEntry represents a dictionary entry: Key: Value. +// Used only within a DictExpr. +type DictEntry struct { + commentsRef + Key Expr + Colon Position + Value Expr +} + +func (x *DictEntry) Span() (start, end Position) { + start, _ = x.Key.Span() + _, end = x.Value.Span() + return start, end +} + +// A LambdaExpr represents an inline function abstraction. +// +// Although they may be added in future, lambda expressions are not +// currently part of the Starlark spec, so their use is controlled by the +// resolver.AllowLambda flag. +type LambdaExpr struct { + commentsRef + Lambda Position + Params []Expr // param = ident | ident=expr | * | *ident | **ident + Body Expr + + Function interface{} // a *resolve.Function, set by resolver +} + +func (x *LambdaExpr) Span() (start, end Position) { + _, end = x.Body.Span() + return x.Lambda, end +} + +// A ListExpr represents a list literal: [ List ]. +type ListExpr struct { + commentsRef + Lbrack Position + List []Expr + Rbrack Position +} + +func (x *ListExpr) Span() (start, end Position) { + return x.Lbrack, x.Rbrack.add("]") +} + +// CondExpr represents the conditional: X if COND else ELSE. +type CondExpr struct { + commentsRef + If Position + Cond Expr + True Expr + ElsePos Position + False Expr +} + +func (x *CondExpr) Span() (start, end Position) { + start, _ = x.True.Span() + _, end = x.False.Span() + return start, end +} + +// A TupleExpr represents a tuple literal: (List). +type TupleExpr struct { + commentsRef + Lparen Position // optional (e.g. in x, y = 0, 1), but required if List is empty + List []Expr + Rparen Position +} + +func (x *TupleExpr) Span() (start, end Position) { + if x.Lparen.IsValid() { + return x.Lparen, x.Rparen + } else { + return Start(x.List[0]), End(x.List[len(x.List)-1]) + } +} + +// A UnaryExpr represents a unary expression: Op X. +// +// As a special case, UnaryOp{Op:Star} may also represent +// the star parameter in def f(*args) or def f(*, x). +type UnaryExpr struct { + commentsRef + OpPos Position + Op Token + X Expr // may be nil if Op==STAR +} + +func (x *UnaryExpr) Span() (start, end Position) { + if x.X != nil { + _, end = x.X.Span() + } else { + end = x.OpPos.add("*") + } + return x.OpPos, end +} + +// A BinaryExpr represents a binary expression: X Op Y. +// +// As a special case, BinaryExpr{Op:EQ} may also +// represent a named argument in a call f(k=v) +// or a named parameter in a function declaration +// def f(param=default). +type BinaryExpr struct { + commentsRef + X Expr + OpPos Position + Op Token + Y Expr +} + +func (x *BinaryExpr) Span() (start, end Position) { + start, _ = x.X.Span() + _, end = x.Y.Span() + return start, end +} + +// A SliceExpr represents a slice or substring expression: X[Lo:Hi:Step]. +type SliceExpr struct { + commentsRef + X Expr + Lbrack Position + Lo, Hi, Step Expr // all optional + Rbrack Position +} + +func (x *SliceExpr) Span() (start, end Position) { + start, _ = x.X.Span() + return start, x.Rbrack +} + +// An IndexExpr represents an index expression: X[Y]. +type IndexExpr struct { + commentsRef + X Expr + Lbrack Position + Y Expr + Rbrack Position +} + +func (x *IndexExpr) Span() (start, end Position) { + start, _ = x.X.Span() + return start, x.Rbrack +} |