/
what.go
210 lines (188 loc) · 5.08 KB
/
what.go
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// Copyright 2013 The Go 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 oracle
import (
"fmt"
"go/ast"
"go/build"
"go/token"
"os"
"path/filepath"
"sort"
"strings"
"golang.org/x/tools/go/ast/astutil"
"golang.org/x/tools/oracle/serial"
)
// what reports all the information about the query selection that can be
// obtained from parsing only its containing source file.
// It is intended to be a very low-latency query callable from GUI
// tools, e.g. to populate a menu of options of slower queries about
// the selected location.
//
func what(q *Query) error {
qpos, err := fastQueryPos(q.Pos)
if err != nil {
return err
}
q.Fset = qpos.fset
// (ignore errors)
srcdir, importPath, _ := guessImportPath(q.Fset.File(qpos.start).Name(), q.Build)
// Determine which query modes are applicable to the selection.
enable := map[string]bool{
"describe": true, // any syntax; always enabled
}
if qpos.end > qpos.start {
enable["freevars"] = true // nonempty selection?
}
for _, n := range qpos.path {
switch n := n.(type) {
case *ast.Ident:
enable["definition"] = true
enable["referrers"] = true
enable["implements"] = true
case *ast.CallExpr:
enable["callees"] = true
case *ast.FuncDecl:
enable["callers"] = true
enable["callstack"] = true
case *ast.SendStmt:
enable["peers"] = true
case *ast.UnaryExpr:
if n.Op == token.ARROW {
enable["peers"] = true
}
}
// For implements, we approximate findInterestingNode.
if _, ok := enable["implements"]; !ok {
switch n.(type) {
case *ast.ArrayType,
*ast.StructType,
*ast.FuncType,
*ast.InterfaceType,
*ast.MapType,
*ast.ChanType:
enable["implements"] = true
}
}
// For pointsto, we approximate findInterestingNode.
if _, ok := enable["pointsto"]; !ok {
switch n.(type) {
case ast.Stmt,
*ast.ArrayType,
*ast.StructType,
*ast.FuncType,
*ast.InterfaceType,
*ast.MapType,
*ast.ChanType:
enable["pointsto"] = false // not an expr
case ast.Expr, ast.Decl, *ast.ValueSpec:
enable["pointsto"] = true // an expr, maybe
default:
// Comment, Field, KeyValueExpr, etc: ascend.
}
}
}
// If we don't have an exact selection, disable modes that need one.
if !qpos.exact {
enable["callees"] = false
enable["pointsto"] = false
enable["whicherrs"] = false
enable["describe"] = false
}
var modes []string
for mode := range enable {
modes = append(modes, mode)
}
sort.Strings(modes)
q.result = &whatResult{
path: qpos.path,
srcdir: srcdir,
importPath: importPath,
modes: modes,
}
return nil
}
// guessImportPath finds the package containing filename, and returns
// its source directory (an element of $GOPATH) and its import path
// relative to it.
//
// TODO(adonovan): what about _test.go files that are not part of the
// package?
//
func guessImportPath(filename string, buildContext *build.Context) (srcdir, importPath string, err error) {
absFile, err := filepath.Abs(filename)
if err != nil {
err = fmt.Errorf("can't form absolute path of %s", filename)
return
}
absFileDir := segments(filepath.Dir(absFile))
// Find the innermost directory in $GOPATH that encloses filename.
minD := 1024
for _, gopathDir := range buildContext.SrcDirs() {
absDir, err := filepath.Abs(gopathDir)
if err != nil {
continue // e.g. non-existent dir on $GOPATH
}
d := prefixLen(segments(absDir), absFileDir)
// If there are multiple matches,
// prefer the innermost enclosing directory
// (smallest d).
if d >= 0 && d < minD {
minD = d
srcdir = gopathDir
importPath = strings.Join(absFileDir[len(absFileDir)-minD:], string(os.PathSeparator))
}
}
if srcdir == "" {
err = fmt.Errorf("directory %s is not beneath any of these GOROOT/GOPATH directories: %s",
filepath.Dir(absFile), strings.Join(buildContext.SrcDirs(), ", "))
}
return
}
func segments(path string) []string {
return strings.Split(path, string(os.PathSeparator))
}
// prefixLen returns the length of the remainder of y if x is a prefix
// of y, a negative number otherwise.
func prefixLen(x, y []string) int {
d := len(y) - len(x)
if d >= 0 {
for i := range x {
if y[i] != x[i] {
return -1 // not a prefix
}
}
}
return d
}
type whatResult struct {
path []ast.Node
modes []string
srcdir string
importPath string
}
func (r *whatResult) display(printf printfFunc) {
for _, n := range r.path {
printf(n, "%s", astutil.NodeDescription(n))
}
printf(nil, "modes: %s", r.modes)
printf(nil, "srcdir: %s", r.srcdir)
printf(nil, "import path: %s", r.importPath)
}
func (r *whatResult) toSerial(res *serial.Result, fset *token.FileSet) {
var enclosing []serial.SyntaxNode
for _, n := range r.path {
enclosing = append(enclosing, serial.SyntaxNode{
Description: astutil.NodeDescription(n),
Start: fset.Position(n.Pos()).Offset,
End: fset.Position(n.End()).Offset,
})
}
res.What = &serial.What{
Modes: r.modes,
SrcDir: r.srcdir,
ImportPath: r.importPath,
Enclosing: enclosing,
}
}