How do I check the size of a Go project? - go

Question

Is there an easy way to check the size of a Golang project? It's not an executable, it's a package that I'm importing in my own project.

Answer 1

You can see how big the library binaries are by looking in the $GOPATH/pkg directory (if $GOPATH is not exported go defaults to $HOME/go).
So to check the size of some of the gorilla http pkgs. Install them first:
$ go get -u github.com/gorilla/mux
$ go get -u github.com/gorilla/securecookie
$ go get -u github.com/gorilla/sessions
The KB binary sizes on my 64-bit MacOS (darwin_amd64):
$ cd $GOPATH/pkg/darwin_amd64/github.com/gorilla/
$ du -k *
284 mux.a
128 securecookie.a
128 sessions.a
EDIT:
Library (package) size is one thing, but how much space that takes up in your executable after the link stage can vary wildly. This is because packages have their own dependencies and with that comes extra baggage, but that baggage may be shared by other packages you import.
An example demonstrates this best:
empty.go:
package main
func main() {}
http.go:
package main
import "net/http"
var _ = http.Serve
func main() {}
mux.go:
package main
import "github.com/gorilla/mux"
var _ = mux.NewRouter
func main() {}
All 3 programs are functionally identical - executing zero user code - but their dependencies differ. The resulting binary sizes in KB:
$ du -k *
1028 empty
5812 http
5832 mux
What does this tell us? The core go pkg net/http adds significant size to our executable. The mux pkg is not large by itself, but it has an import dependency on net/http pkg - hence the significant file size for it too. Yet the delta between mux and http is only 20KB, whereas the listed file size of the mux.a library is 284KB. So we can't simply add the library pkg sizes to determine their true footprint.
Conclusion:
The go linker will strip out a lot of baggage from individual libraries during the build process, but in order to get a true sense of how much extra weight importing certain packages, one has to look at all of the pkg's sub-dependencies as well.

Answer 2

Here is another solution that makes use of https://pkg.go.dev/golang.org/x/tools/go/packages
I took the example provided by the author, and slightly updated it with the demonstration binary available here.
package main
import (
"flag"
"fmt"
"log"
"os"
"sort"
"golang.org/x/tools/go/packages"
)
func main() {
flag.Parse()
// Many tools pass their command-line arguments (after any flags)
// uninterpreted to packages.Load so that it can interpret them
// according to the conventions of the underlying build system.
cfg := &packages.Config{Mode: packages.NeedFiles |
packages.NeedSyntax |
packages.NeedImports,
}
pkgs, err := packages.Load(cfg, flag.Args()...)
if err != nil {
fmt.Fprintf(os.Stderr, "load: %v\n", err)
os.Exit(1)
}
if packages.PrintErrors(pkgs) > 0 {
os.Exit(1)
}
// Print the names of the source files
// for each package listed on the command line.
var size int64
for _, pkg := range pkgs {
for _, file := range pkg.GoFiles {
s, err := os.Stat(file)
if err != nil {
log.Println(err)
continue
}
size += s.Size()
}
}
fmt.Printf("size of %v is %v b\n", pkgs[0].ID, size)
size = 0
for _, pkg := range allPkgs(pkgs) {
for _, file := range pkg.GoFiles {
s, err := os.Stat(file)
if err != nil {
log.Println(err)
continue
}
size += s.Size()
}
}
fmt.Printf("size of %v and deps is %v b\n", pkgs[0].ID, size)
}
func allPkgs(lpkgs []*packages.Package) []*packages.Package {
var all []*packages.Package // postorder
seen := make(map[*packages.Package]bool)
var visit func(*packages.Package)
visit = func(lpkg *packages.Package) {
if !seen[lpkg] {
seen[lpkg] = true
// visit imports
var importPaths []string
for path := range lpkg.Imports {
importPaths = append(importPaths, path)
}
sort.Strings(importPaths) // for determinism
for _, path := range importPaths {
visit(lpkg.Imports[path])
}
all = append(all, lpkg)
}
}
for _, lpkg := range lpkgs {
visit(lpkg)
}
return all
}

Answer 3

You can download all the imported modules with go mod vendor, then count the lines of all the .go files that aren't test files:
package main
import (
"bytes"
"fmt"
"io/fs"
"os"
"os/exec"
"path/filepath"
"strings"
)
func count(mod string) int {
imp := fmt.Sprintf("package main\nimport _ %q", mod)
os.WriteFile("size.go", []byte(imp), os.ModePerm)
exec.Command("go", "mod", "init", "size").Run()
exec.Command("go", "mod", "vendor").Run()
var count int
filepath.WalkDir("vendor", func(s string, d fs.DirEntry, err error) error {
if strings.HasSuffix(s, ".go") && !strings.HasSuffix(s, "_test.go") {
data, err := os.ReadFile(s)
if err != nil {
return err
}
count += bytes.Count(data, []byte{'\n'})
}
return nil
})
return count
}
func main() {
println(count("github.com/klauspost/compress/zstd"))
}