Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Allow linker to perform deadcode elimination for program using Cobra #1956

Open
wants to merge 3 commits into
base: main
Choose a base branch
from
Open
Show file tree
Hide file tree
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
16 changes: 10 additions & 6 deletions cobra.go
Original file line number Diff line number Diff line change
Expand Up @@ -176,12 +176,16 @@ func rpad(s string, padding int) string {
return fmt.Sprintf(formattedString, s)
}

// tmpl executes the given template text on data, writing the result to w.
func tmpl(w io.Writer, text string, data interface{}) error {
t := template.New("top")
t.Funcs(templateFuncs)
template.Must(t.Parse(text))
return t.Execute(w, data)
func tmpl(text string) *tmplFunc {
return &tmplFunc{
tmpl: text,
fn: func(w io.Writer, data interface{}) error {
t := template.New("top")
t.Funcs(templateFuncs)
template.Must(t.Parse(text))
return t.Execute(w, data)
},
}
}

// ld compares two strings and returns the levenshtein distance between them.
Expand Down
72 changes: 72 additions & 0 deletions cobra_test.go
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,10 @@
package cobra

import (
"os"
"os/exec"
"path/filepath"
"strings"
"testing"
"text/template"
)
Expand Down Expand Up @@ -222,3 +226,71 @@ func TestRpad(t *testing.T) {
})
}
}

Copy link
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Can you add a comment above this test explaining that deadcode elimination is reduced when MethodByName is present which will affect all programs using cobra; so this test make sure we don't introduce code that depends on MethodByName().

Also please put a comment with the URL of this PR.

Copy link
Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

See if you like what I wrote.

// TestDeadcodeElimination checks that a simple program using cobra in its
// default configuration is linked taking full advantage of the linker's
// deadcode elimination step.
//
// If reflect.Value.MethodByName/reflect.Value.Method are reachable the
// linker will not always be able to prove that exported methods are
// unreachable, making deadcode elimination less effective. Using
// text/template and html/template makes reflect.Value.MethodByName
// reachable.
// Since cobra can use text/template templates this test checks that in its
// default configuration that code path can be proven to be unreachable by
// the linker.
//
// See also: https://github.com/spf13/cobra/pull/1956
func TestDeadcodeElimination(t *testing.T) {
// check that a simple program using cobra in its default configuration is
// linked with deadcode elimination enabled.
const (
dirname = "test_deadcode"
progname = "test_deadcode_elimination"
)
_ = os.Mkdir(dirname, 0770)
defer os.RemoveAll(dirname)
filename := filepath.Join(dirname, progname+".go")
err := os.WriteFile(filename, []byte(`package main

import (
"fmt"
"os"

"github.com/spf13/cobra"
)

var rootCmd = &cobra.Command{
Version: "1.0",
Use: "example_program",
Short: "example_program - test fixture to check that deadcode elimination is allowed",
Run: func(cmd *cobra.Command, args []string) {
fmt.Println("hello world")
},
Aliases: []string{"alias1", "alias2"},
Example: "stringer --help",
}

func main() {
if err := rootCmd.Execute(); err != nil {
fmt.Fprintf(os.Stderr, "Whoops. There was an error while executing your CLI '%s'", err)
os.Exit(1)
}
}
`), 0600)
if err != nil {
t.Fatalf("could not write test program: %v", err)
}
buf, err := exec.Command("go", "build", filename).CombinedOutput()
if err != nil {
t.Fatalf("could not compile test program: %s", string(buf))
}
defer os.Remove(progname)
buf, err = exec.Command("go", "tool", "nm", progname).CombinedOutput()
if err != nil {
t.Fatalf("could not run go tool nm: %v", err)
}
if strings.Contains(string(buf), "MethodByName") {
t.Error("compiled programs contains MethodByName symbol")
}
}
Loading
Loading