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// Copyright 2019 Google LLC.
// SPDX-License-Identifier: Apache-2.0
// This tool analyses external (i.e. not built with `buildGo.nix`) Go
// packages to determine a build plan that Nix can import.
package main
import (
"encoding/json"
"flag"
"fmt"
"go/build"
"io/ioutil"
"log"
"os"
"path"
"path/filepath"
"strings"
)
// Path to a JSON file describing all standard library import paths.
// This file is generated and set here by Nix during the build
// process.
var stdlibList string
// pkg describes a single Go package within the specified source
// directory.
//
// Return information includes the local (relative from project root)
// and external (none-stdlib) dependencies of this package.
type pkg struct {
Name []string `json:"name"`
Files []string `json:"files"`
LocalDeps [][]string `json:"localDeps"`
ForeignDeps []string `json:"foreignDeps"`
}
// findGoDirs returns a filepath.WalkFunc that identifies all
// directories that contain Go source code in a certain tree.
func findGoDirs(at string) ([]string, error) {
dirSet := make(map[string]bool)
err := filepath.Walk(at, func(path string, info os.FileInfo, err error) error {
// Skip folders that are guaranteed to not be relevant
if info.IsDir() && (info.Name() == "testdata" || info.Name() == ".git") {
return filepath.SkipDir
}
// If the current file is a Go file, then the directory is popped
// (i.e. marked as a Go directory).
if !info.IsDir() && strings.HasSuffix(info.Name(), ".go") && !strings.HasSuffix(info.Name(), "_test.go") {
dirSet[filepath.Dir(path)] = true
}
return nil
})
if err != nil {
return nil, err
}
goDirs := []string{}
for k, _ := range dirSet {
goDirs = append(goDirs, k)
}
return goDirs, nil
}
// analysePackage loads and analyses the imports of a single Go
// package, returning the data that is required by the Nix code to
// generate a derivation for this package.
func analysePackage(root, source, importpath string, stdlib map[string]bool) (pkg, error) {
ctx := build.Default
p, err := ctx.ImportDir(source, build.IgnoreVendor)
if err != nil {
return pkg{}, err
}
local := [][]string{}
foreign := []string{}
for _, i := range p.Imports {
if stdlib[i] {
continue
}
if strings.HasPrefix(i, importpath) {
local = append(local, strings.Split(strings.TrimPrefix(i, importpath+"/"), "/"))
} else {
foreign = append(foreign, i)
}
}
prefix := strings.TrimPrefix(source, root+"/")
name := []string{}
if len(prefix) != len(source) {
name = strings.Split(prefix, "/")
} else {
// Otherwise, the name is empty since its the root package and no
// prefix should be added to files.
prefix = ""
}
files := []string{}
for _, f := range p.GoFiles {
files = append(files, path.Join(prefix, f))
}
return pkg{
Name: name,
Files: files,
LocalDeps: local,
ForeignDeps: foreign,
}, nil
}
func loadStdlibPkgs(from string) (pkgs map[string]bool, err error) {
f, err := ioutil.ReadFile(from)
if err != nil {
return
}
err = json.Unmarshal(f, &pkgs)
return
}
func main() {
source := flag.String("source", "", "path to directory with sources to process")
path := flag.String("path", "", "import path for the package")
flag.Parse()
if *source == "" {
log.Fatalf("-source flag must be specified")
}
stdlibPkgs, err := loadStdlibPkgs(stdlibList)
if err != nil {
log.Fatalf("failed to load standard library index from %q: %s\n", stdlibList, err)
}
goDirs, err := findGoDirs(*source)
if err != nil {
log.Fatalf("failed to walk source directory '%s': %s\n", source, err)
}
all := []pkg{}
for _, d := range goDirs {
analysed, err := analysePackage(*source, d, *path, stdlibPkgs)
if err != nil {
log.Fatalf("failed to analyse package at %q: %s", d, err)
}
all = append(all, analysed)
}
j, _ := json.Marshal(all)
fmt.Println(string(j))
}
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