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source.go
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source.go
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package source
import (
"fmt"
"go/ast"
"go/parser"
"go/token"
)
type Searcher struct {
fileset *token.FileSet
visited map[string]*ast.File
}
func New() *Searcher {
return &Searcher{fileset: token.NewFileSet(), visited: make(map[string]*ast.File)}
}
type NoNodeError struct {
f string
l int
}
func (n NoNodeError) Error() string {
return fmt.Sprintf("could not find node at %s:%d", n.f, n.l)
}
// Returns the first node at the given file:line.
func (s *Searcher) FirstNodeAt(fname string, line int) (ast.Node, error) {
var node ast.Node
f, err := s.parse(fname)
if err != nil {
return nil, err
}
ast.Inspect(f, func(n ast.Node) bool {
if n == nil {
return true
}
position := s.fileset.Position(n.Pos())
if position.Line == line {
node = n
return false
}
return true
})
if node == nil {
return nil, NoNodeError{f: fname, l: line}
}
return node, nil
}
type Done string
func (d Done) Error() string {
return string(d)
}
// Returns all possible lines that could be executed after the given file:line,
// within the same source file.
func (s *Searcher) NextLines(fname string, line int) (lines []int, err error) {
var found bool
n, err := s.FirstNodeAt(fname, line)
if err != nil {
return lines, nil
}
defer func() {
if e := recover(); e != nil {
nl := make([]int, 0, len(lines))
fnd := make(map[int]bool)
for _, l := range lines {
if _, ok := fnd[l]; !ok {
fnd[l] = true
nl = append(nl, l)
}
}
lines = nl
}
}()
switch x := n.(type) {
// Check if we are at an 'if' statement.
//
// If we are at an 'if' statement, employ the following algorithm:
// * Follow all 'else if' statements, appending their line number
// * Follow any 'else' statement if it exists, appending the line
// number of the statement following the 'else'.
// * If there is no 'else' statement, append line of first statement
// following the entire 'if' block.
case *ast.IfStmt:
var rbrace int
p := x.Body.List[0].Pos()
pos := s.fileset.Position(p)
lines = append(lines, pos.Line)
if x.Else == nil {
// Grab first line after entire 'if' block
rbrace = s.fileset.Position(x.Body.Rbrace).Line
f, err := s.parse(fname)
if err != nil {
return nil, err
}
ast.Inspect(f, func(n ast.Node) bool {
if n == nil {
return true
}
pos := s.fileset.Position(n.Pos())
if rbrace < pos.Line {
lines = append(lines, pos.Line)
panic(Done("done"))
}
return true
})
} else {
// Follow any 'else' statements
for {
if stmt, ok := x.Else.(*ast.IfStmt); ok {
pos := s.fileset.Position(stmt.Pos())
lines = append(lines, pos.Line)
x = stmt
continue
}
pos := s.fileset.Position(x.Else.Pos())
ast.Inspect(x, func(n ast.Node) bool {
if found {
panic(Done("done"))
}
if n == nil {
return false
}
p := s.fileset.Position(n.Pos())
if pos.Line < p.Line {
lines = append(lines, p.Line)
found = true
return false
}
return true
})
}
}
// Follow case statements.
//
// Append line for first statement following each 'case' condition.
case *ast.SwitchStmt:
ast.Inspect(x, func(n ast.Node) bool {
if stmt, ok := n.(*ast.SwitchStmt); ok {
ast.Inspect(stmt, func(n ast.Node) bool {
if stmt, ok := n.(*ast.CaseClause); ok {
p := stmt.Body[0].Pos()
pos := s.fileset.Position(p)
lines = append(lines, pos.Line)
return false
}
return true
})
panic(Done("done"))
}
return true
})
// Default case - find next source line.
//
// We are not at a branch, employ the following algorithm:
// * Traverse tree, storing any loop as a parent
// * Find next source line after the given line
// * Check and see if we've passed the scope of any parent we've
// stored. If so, pop them off the stack. The last parent that
// is left get's appending to our list of lines since we could
// end up at the top of the loop again.
default:
var (
parents []*ast.BlockStmt
parentBlockBeginLine int
deferEndLine int
)
f, err := s.parse(fname)
if err != nil {
return nil, err
}
ast.Inspect(f, func(n ast.Node) bool {
if found {
panic(Done("done"))
}
if n == nil {
return true
}
pos := s.fileset.Position(n.Pos())
if line < pos.Line && deferEndLine != 0 {
p := s.fileset.Position(n.Pos())
if deferEndLine < p.Line {
found = true
lines = append(lines, p.Line)
return false
}
}
if stmt, ok := n.(*ast.ForStmt); ok {
parents = append(parents, stmt.Body)
pos := s.fileset.Position(stmt.Pos())
parentBlockBeginLine = pos.Line
}
if _, ok := n.(*ast.GenDecl); ok {
return true
}
if dn, ok := n.(*ast.DeferStmt); ok && line < pos.Line {
endpos := s.fileset.Position(dn.End())
deferEndLine = endpos.Line
return false
}
if st, ok := n.(*ast.DeclStmt); ok {
beginpos := s.fileset.Position(st.Pos())
endpos := s.fileset.Position(st.End())
if beginpos.Line < endpos.Line {
return true
}
}
// Check to see if we've found the "next" line.
if line < pos.Line {
if _, ok := n.(*ast.BlockStmt); ok {
return true
}
var (
parent *ast.BlockStmt
parentEndLine int
)
for len(parents) > 0 {
parent = parents[len(parents)-1]
// Grab the line number of the right brace of the parent block.
parentEndLine = s.fileset.Position(parent.Rbrace).Line
// Check to see if we're still within the parents block.
// If we are, we're done and that is our parent.
if parentEndLine > line {
parentBlockBeginLine = s.fileset.Position(parent.Pos()).Line
break
}
// If we weren't, and there is only 1 parent, we no longer have one.
if len(parents) == 1 {
parent = nil
break
}
// Remove that parent from the stack.
parents = parents[0 : len(parents)-1]
}
if parent != nil {
var (
endfound bool
beginFound bool
beginLine int
)
ast.Inspect(f, func(n ast.Node) bool {
if n == nil || endfound {
return false
}
if _, ok := n.(*ast.BlockStmt); ok {
return true
}
pos := s.fileset.Position(n.Pos())
if parentBlockBeginLine < pos.Line && !beginFound {
beginFound = true
beginLine = pos.Line
return true
}
if parentEndLine < pos.Line {
if _, ok := n.(*ast.FuncDecl); !ok {
lines = append(lines, beginLine, pos.Line)
}
endfound = true
return false
}
return true
})
lines = append(lines, parentBlockBeginLine)
}
switch n.(type) {
case *ast.BranchStmt, *ast.FuncDecl:
default:
lines = append(lines, pos.Line)
}
found = true
return false
}
return true
})
if len(lines) == 0 && 0 < len(parents) {
parent := parents[len(parents)-1]
lbrace := s.fileset.Position(parent.Lbrace).Line
pos := s.fileset.Position(parent.List[0].Pos())
lines = append(lines, lbrace, pos.Line)
}
}
return lines, nil
}
// Parses file named by fname, caching files it has already parsed.
func (s *Searcher) parse(fname string) (*ast.File, error) {
if f, ok := s.visited[fname]; ok {
return f, nil
}
f, err := parser.ParseFile(s.fileset, fname, nil, 0)
if err != nil {
return nil, err
}
s.visited[fname] = f
return f, nil
}