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// Copyright 2018 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 packages
// This file defines the protocol that enables an external "driver"
// tool to supply package metadata in place of 'go list'.
import (
"bytes"
"encoding/json"
"fmt"
"os"
"os/exec"
"strings"
)
// DriverRequest defines the schema of a request for package metadata
// from an external driver program. The JSON-encoded DriverRequest
// message is provided to the driver program's standard input. The
// query patterns are provided as command-line arguments.
//
// See the package documentation for an overview.
type DriverRequest struct {
Mode LoadMode `json:"mode"`
// Env specifies the environment the underlying build system should be run in.
Env []string `json:"env"`
// BuildFlags are flags that should be passed to the underlying build system.
BuildFlags []string `json:"build_flags"`
// Tests specifies whether the patterns should also return test packages.
Tests bool `json:"tests"`
// Overlay maps file paths (relative to the driver's working directory)
// to the contents of overlay files (see Config.Overlay).
Overlay map[string][]byte `json:"overlay"`
}
// DriverResponse defines the schema of a response from an external
// driver program, providing the results of a query for package
// metadata. The driver program must write a JSON-encoded
// DriverResponse message to its standard output.
//
// See the package documentation for an overview.
type DriverResponse struct {
// NotHandled is returned if the request can't be handled by the current
// driver. If an external driver returns a response with NotHandled, the
// rest of the DriverResponse is ignored, and go/packages will fallback
// to the next driver. If go/packages is extended in the future to support
// lists of multiple drivers, go/packages will fall back to the next driver.
NotHandled bool
// Compiler and Arch are the arguments pass of types.SizesFor
// to get a types.Sizes to use when type checking.
Compiler string
Arch string
// Roots is the set of package IDs that make up the root packages.
// We have to encode this separately because when we encode a single package
// we cannot know if it is one of the roots as that requires knowledge of the
// graph it is part of.
Roots []string `json:",omitempty"`
// Packages is the full set of packages in the graph.
// The packages are not connected into a graph.
// The Imports if populated will be stubs that only have their ID set.
// Imports will be connected and then type and syntax information added in a
// later pass (see refine).
Packages []*Package
// GoVersion is the minor version number used by the driver
// (e.g. the go command on the PATH) when selecting .go files.
// Zero means unknown.
GoVersion int
}
// driver is the type for functions that query the build system for the
// packages named by the patterns.
type driver func(cfg *Config, patterns ...string) (*DriverResponse, error)
// findExternalDriver returns the file path of a tool that supplies
// the build system package structure, or "" if not found."
// If GOPACKAGESDRIVER is set in the environment findExternalTool returns its
// value, otherwise it searches for a binary named gopackagesdriver on the PATH.
func findExternalDriver(cfg *Config) driver {
const toolPrefix = "GOPACKAGESDRIVER="
tool := ""
for _, env := range cfg.Env {
if val := strings.TrimPrefix(env, toolPrefix); val != env {
tool = val
}
}
if tool != "" && tool == "off" {
return nil
}
if tool == "" {
var err error
tool, err = exec.LookPath("gopackagesdriver")
if err != nil {
return nil
}
}
return func(cfg *Config, words ...string) (*DriverResponse, error) {
req, err := json.Marshal(DriverRequest{
Mode: cfg.Mode,
Env: cfg.Env,
BuildFlags: cfg.BuildFlags,
Tests: cfg.Tests,
Overlay: cfg.Overlay,
})
if err != nil {
return nil, fmt.Errorf("failed to encode message to driver tool: %v", err)
}
buf := new(bytes.Buffer)
stderr := new(bytes.Buffer)
cmd := exec.CommandContext(cfg.Context, tool, words...)
cmd.Dir = cfg.Dir
// The cwd gets resolved to the real path. On Darwin, where
// /tmp is a symlink, this breaks anything that expects the
// working directory to keep the original path, including the
// go command when dealing with modules.
//
// os.Getwd stdlib has a special feature where if the
// cwd and the PWD are the same node then it trusts
// the PWD, so by setting it in the env for the child
// process we fix up all the paths returned by the go
// command.
//
// (See similar trick in Invocation.run in ../../internal/gocommand/invoke.go)
cmd.Env = append(slicesClip(cfg.Env), "PWD="+cfg.Dir)
cmd.Stdin = bytes.NewReader(req)
cmd.Stdout = buf
cmd.Stderr = stderr
if err := cmd.Run(); err != nil {
return nil, fmt.Errorf("%v: %v: %s", tool, err, cmd.Stderr)
}
if len(stderr.Bytes()) != 0 && os.Getenv("GOPACKAGESPRINTDRIVERERRORS") != "" {
fmt.Fprintf(os.Stderr, "%s stderr: <<%s>>\n", cmdDebugStr(cmd), stderr)
}
var response DriverResponse
if err := json.Unmarshal(buf.Bytes(), &response); err != nil {
return nil, err
}
return &response, nil
}
}
// slicesClip removes unused capacity from the slice, returning s[:len(s):len(s)].
// TODO(adonovan): use go1.21 slices.Clip.
func slicesClip[S ~[]E, E any](s S) S { return s[:len(s):len(s)] }
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