102 lines
3.4 KiB
Go
102 lines
3.4 KiB
Go
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// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This file enables an external tool to intercept package requests.
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// If the tool is present then its results are used in preference to
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// the go list command.
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package packages
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import (
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"bytes"
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"encoding/json"
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"fmt"
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"os"
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"os/exec"
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"strings"
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)
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// The Driver Protocol
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//
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// The driver, given the inputs to a call to Load, returns metadata about the packages specified.
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// This allows for different build systems to support go/packages by telling go/packages how the
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// packages' source is organized.
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// The driver is a binary, either specified by the GOPACKAGESDRIVER environment variable or in
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// the path as gopackagesdriver. It's given the inputs to load in its argv. See the package
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// documentation in doc.go for the full description of the patterns that need to be supported.
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// A driver receives as a JSON-serialized driverRequest struct in standard input and will
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// produce a JSON-serialized driverResponse (see definition in packages.go) in its standard output.
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// driverRequest is used to provide the portion of Load's Config that is needed by a driver.
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type driverRequest struct {
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Mode LoadMode `json:"mode"`
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// Env specifies the environment the underlying build system should be run in.
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Env []string `json:"env"`
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// BuildFlags are flags that should be passed to the underlying build system.
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BuildFlags []string `json:"build_flags"`
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// Tests specifies whether the patterns should also return test packages.
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Tests bool `json:"tests"`
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// Overlay maps file paths (relative to the driver's working directory) to the byte contents
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// of overlay files.
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Overlay map[string][]byte `json:"overlay"`
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}
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// findExternalDriver returns the file path of a tool that supplies
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// the build system package structure, or "" if not found."
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// If GOPACKAGESDRIVER is set in the environment findExternalTool returns its
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// value, otherwise it searches for a binary named gopackagesdriver on the PATH.
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func findExternalDriver(cfg *Config) driver {
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const toolPrefix = "GOPACKAGESDRIVER="
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tool := ""
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for _, env := range cfg.Env {
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if val := strings.TrimPrefix(env, toolPrefix); val != env {
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tool = val
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}
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}
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if tool != "" && tool == "off" {
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return nil
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}
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if tool == "" {
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var err error
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tool, err = exec.LookPath("gopackagesdriver")
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if err != nil {
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return nil
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}
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}
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return func(cfg *Config, words ...string) (*driverResponse, error) {
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req, err := json.Marshal(driverRequest{
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Mode: cfg.Mode,
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Env: cfg.Env,
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BuildFlags: cfg.BuildFlags,
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Tests: cfg.Tests,
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Overlay: cfg.Overlay,
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})
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if err != nil {
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return nil, fmt.Errorf("failed to encode message to driver tool: %v", err)
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}
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buf := new(bytes.Buffer)
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stderr := new(bytes.Buffer)
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cmd := exec.CommandContext(cfg.Context, tool, words...)
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cmd.Dir = cfg.Dir
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cmd.Env = cfg.Env
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cmd.Stdin = bytes.NewReader(req)
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cmd.Stdout = buf
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cmd.Stderr = stderr
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if err := cmd.Run(); err != nil {
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return nil, fmt.Errorf("%v: %v: %s", tool, err, cmd.Stderr)
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}
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if len(stderr.Bytes()) != 0 && os.Getenv("GOPACKAGESPRINTDRIVERERRORS") != "" {
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fmt.Fprintf(os.Stderr, "%s stderr: <<%s>>\n", cmdDebugStr(cmd, words...), stderr)
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}
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var response driverResponse
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if err := json.Unmarshal(buf.Bytes(), &response); err != nil {
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return nil, err
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}
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return &response, nil
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}
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}
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