Format

Summary

./godelw format formats all of the Go files in a project by running gofmt and ptimports on them.

Tutorial start state

• $GOPATH/src/github.com/nmiyake/echgo exists and is the working directory
• Project contains godel and godelw
• Project contains main.go
• Project contains .gitignore that ignores IDEA files

(Link)

Format code

Update the program code to put the echo functionality into a separate package and call it from the main project:

➜ mkdir -p echo
➜ echo 'package echo
func Echo(in string) string {
	fmt.Println(strings.Join(os.Args[1:], " "))
}' > echo/echo.go
➜ echo 'package main

import (
	"fmt"
	"os"
	"strings"
	"github.com/nmiyake/echgo/echo"
)

func main() {
	fmt.Println(echo.Echo(strings.Join(os.Args[1:], " ")))
}' > main.go

Stage these files as a git commit:

➜ git add echo main.go
➜ git status
On branch master
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

	new file:   echo/echo.go
	modified:   main.go

Run ./godelw format to format all of the files in the project:

➜ ./godelw format

This command formats all of the files using gofmt and ptimports. Verify that this command modified the files:

➜ git status
On branch master
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

	new file:   echo/echo.go
	modified:   main.go

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

	modified:   echo/echo.go
	modified:   main.go

➜ git diff | cat
diff --git a/echo/echo.go b/echo/echo.go
index f7d4dbe..3e055c2 100644
--- a/echo/echo.go
+++ b/echo/echo.go
@@ -1,4 +1,5 @@
 package echo
+
 func Echo(in string) string {
 	fmt.Println(strings.Join(os.Args[1:], " "))
 }
diff --git a/main.go b/main.go
index 1d9820b..9087898 100644
--- a/main.go
+++ b/main.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"strings"
+
 	"github.com/nmiyake/echgo/echo"
 )

In main.go, note how the github.com/nmiyake/echgo/echo import has been separated from the other imports. ptimports groups imports into distinct sections consisting of the standard library imports, external imports and imports that are part of the same package.

Commit the formatted files:

➜ git add main.go echo
➜ git commit -m "Create echo package"
[master 24f63f7] Create echo package
 2 files changed, 8 insertions(+), 1 deletion(-)
 create mode 100644 echo/echo.go
➜ git status
On branch master
nothing to commit, working directory clean

Tutorial end state

• $GOPATH/src/github.com/nmiyake/echgo exists and is the working directory
• Project contains godel and godelw
• Project contains main.go
• Project contains .gitignore that ignores IDEA files
• Project contains echo/echo.go

(Link)

Tutorial next step

Run static checks on code

More

Differences between ./godelw format and gofmt -w ./...

./godelw format has the following advantages over running gofmt -w ./...

• Only formats files that are part of the project (does not format files in excluded directories)
• Runs ptimports in addition to gofmt

ptimports groups Go imports into 3 groups: the Go standard library, packages that are not part of the current project and packages that are part of the current project.

The output of ./godelw format is compatible with gofmt (that is, it is guaranteed that applying gofmt to a file formatted by ./godelw format will be a no-op).

--list flag

Running ./godelw format with the --list (or -l) flag will output the files that would be changed if ./godelw format were run without actually applying the changes.