feat: getsolc binary to locate or download Solidity compiler

scripts/getsolc/main.go

@@ -0,0 +1,154 @@
+// The getsolc binary downloads the Solidity compiler from official sources. If
+// a `solc` binary in the PATH is of the requested version then a symlink is
+// created instead of downloading a new copy.
+package main
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"os/exec"
+	"path"
+	"runtime"
+	"strings"
+
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+func main() {
+	var c config
+
+	flag.StringVar(&c.version, "version", latestVersion, fmt.Sprintf("Version of solc; {major}.{minor}.{patch} or %q", latestVersion))
+	flag.StringVar(&c.outputFile, "out", "./solc", "Path to which the `solc` binary will be saved")
+	flag.BoolVar(&c.ignoreGOARCH, "ignore_goarch", false, "Download amd64 binary even if on another architecture")
+
+	flag.Parse()
+
+	if err := c.run(context.Background()); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+const latestVersion = "latest"
+
+type config struct {
+	version, outputFile string
+	ignoreGOARCH        bool
+}
+
+func (c *config) run(ctx context.Context) error {
+	goos := runtime.GOOS
+	switch goos {
+	case "darwin":
+		goos = "macosx"
+	case "linux":
+	default:
+		return fmt.Errorf("unsupported OS %q", goos)
+	}
+
+	// solc only provides amd64 binaries, but this can be ignored if there is a
+	// translator (e.g. Rosetta on MacOS)
+	if !c.ignoreGOARCH && runtime.GOARCH != "amd64" {
+		return fmt.Errorf("unsupported GOARCH %q", runtime.GOARCH)
+	}
+
+	jsonList, err := httpGetSolFile(ctx, goos, "list.json")
+	if err != nil {
+		return err
+	}
+	defer jsonList.Body.Close()
+	var list solcList
+	if err := json.NewDecoder(jsonList.Body).Decode(&list); err != nil {
+		return err
+	}
+
+	if c.version == latestVersion {
+		c.version = list.LatestRelease
+	}
+	if p, ok := c.bestEffortFindInPATH(ctx); ok { // NOTE: this is not an error path
+		fmt.Fprintf(os.Stderr, "Creating symlink from %q to %q\n", p, c.outputFile)
+		return os.Link(p, c.outputFile)
+	}
+	fmt.Fprintln(os.Stderr, "Downloading solc...")
+
+	solc, err := httpGetSolFile(ctx, goos, list.Releases[c.version])
+	if err != nil {
+		return err
+	}
+	defer solc.Body.Close()
+
+	hash := crypto.NewKeccakState()
+	tee := io.TeeReader(solc.Body, hash)
+
+	out, err := os.OpenFile(c.outputFile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0755)
+	if err != nil {
+		return fmt.Errorf("os.OpenFile: %v", err)
+	}
+	if _, err := io.Copy(out, tee); err != nil {
+		return fmt.Errorf("io.Copy: %v", err)
+	}
+	if err := out.Close(); err != nil {
+		return err
+	}
+
+	fmt.Fprintf(os.Stderr, "Keccak256 of download: %#x\n", hash.Sum(nil))
+	return nil
+}
+
+// httpGetSolFile issues an HTTP(s) GET to download the specified file from the
+// official binaries.soliditylang.org source. `goos` can be either linux or
+// macosx, and file can be "list.json" or any of the paths in [solcList].
+func httpGetSolFile(ctx context.Context, goos, file string) (*http.Response, error) {
+	u := url.URL{
+		Scheme: "https",
+		Host:   "binaries.soliditylang.org",
+		Path:   path.Join(fmt.Sprintf("%s-amd64", goos), file),
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
+	if err != nil {
+		return nil, err
+	}
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil || resp.StatusCode != 200 {
+		return nil, fmt.Errorf("HTTP GET %q; Status = %d; err = %v", u.String(), resp.StatusCode, err)
+	}
+	return resp, nil
+}
+
+// solcList mirrors the JSON lists published by the solc team; e.g:
+// https://binaries.soliditylang.org/linux-amd64/list.json
+type solcList struct {
+	Releases      map[string]string `json:"releases"`
+	LatestRelease string            `json:"latestRelease"`
+	Builds        []struct {
+		Path, Version, Build, Keccak256 string
+		LongVersion                     string `json:"longVersion"`
+		SHA256                          string `json:"sha256"`
+	} `json:"builds"`
+}
+
+// bestEffortFindInPATH attempts to find `solc` in the PATH and, if it has the
+// required version, the path to said binary is returned. The boolean indicates
+// succesful location of a matching binary.
+func (c *config) bestEffortFindInPATH(ctx context.Context) (string, bool) {
+	solc := exec.CommandContext(ctx, "solc", "--version")
+	out, err := solc.CombinedOutput()
+	if err != nil || !bytes.Contains(out, []byte(c.version)) {
+		return "", false
+	}
+
+	which := exec.CommandContext(ctx, "which", "solc")
+	solcPath, err := which.CombinedOutput()
+	if err != nil {
+		return "", false
+	}
+	return strings.TrimSpace(string(solcPath)), true
+}