Attachments in v5 returning 404 and type application/json

[henderb]

This code works in v4, but when run in v5, the browser says ERR_INVALID_RESPONSE

package main

import (
	"encoding/csv"
	"errors"
	"log"
	"net/http"
	"os"
	"strconv"

	"github.com/labstack/echo/v4"
	"github.com/labstack/echo/v4/middleware"
)

type Item struct {
	Name  string
	Price float64
	Cost  float64
}

func main() {
	e := echo.New()
	e.Use(middleware.RequestLogger())
	e.Use(middleware.Gzip())

	e.GET("/data.csv", func(c echo.Context) error {

		items := []Item{
			Item{
				Name:  "Item 1",
				Price: 10.99,
				Cost:  4.63,
			},
			Item{
				Name:  "Item 2",
				Price: 20.99,
				Cost:  12.82,
			},
		}

		f, err := os.CreateTemp("/tmp/", "data-*.csv")
		if err != nil {
			e.Logger.Error("Could not create data temp file", err)
			return c.HTML(500, "Could not create data temp file")
		}
		defer f.Close()

		ic := csv.NewWriter(f)
		ic.Write([]string{
			"Name",
			"Price",
			"Cost"})
		for _, item := range items {
			row := []string{
				item.Name,
				strconv.FormatFloat(item.Price, 'f', 2, 64),
				strconv.FormatFloat(item.Cost, 'f', 3, 64)}

			ic.Write(row)
		}
		ic.Flush()

		return c.Attachment(f.Name(), "data.csv")
	})

	if err := e.Start(":8080"); err != nil && !errors.Is(err, http.ErrServerClosed) {
		log.Fatal(err)
	}
}

v5:

package main

import (
	"encoding/csv"
	"errors"
	"log"
	"net/http"
	"os"
	"strconv"

	"github.com/labstack/echo/v5"
	"github.com/labstack/echo/v5/middleware"
)

type Item struct {
	Name  string
	Price float64
	Cost  float64
}

func main() {
	e := echo.New()
	e.Use(middleware.RequestLogger())
	e.Use(middleware.Gzip())

	e.GET("/data.csv", func(c *echo.Context) error {

		items := []Item{
			Item{
				Name:  "Item 1",
				Price: 10.99,
				Cost:  4.63,
			},
			Item{
				Name:  "Item 2",
				Price: 20.99,
				Cost:  12.82,
			},
		}

		f, err := os.CreateTemp("/tmp/", "data-*.csv")
		if err != nil {
			e.Logger.Error("Could not create data temp file", err)
			return c.HTML(500, "Could not create data temp file")
		}
		defer f.Close()

		ic := csv.NewWriter(f)
		ic.Write([]string{
			"Name",
			"Price",
			"Cost"})
		for _, item := range items {
			row := []string{
				item.Name,
				strconv.FormatFloat(item.Price, 'f', 2, 64),
				strconv.FormatFloat(item.Cost, 'f', 3, 64)}

			ic.Write(row)
		}
		ic.Flush()

		return c.Attachment(f.Name(), "data.csv")
	})

	if err := e.Start(":8080"); err != nil && !errors.Is(err, http.ErrServerClosed) {
		log.Fatal(err)
	}
}

[aldas]

in v5 the default e.Filesystem is set to CWD current working directory and file related methods need to take account that filepath need adjusting

You can set your filesystem to /tmp with

e.Filesystem = os.DirFS("/tmp")

and when you serve the file the path must be trimmed from /tmp prefix

return c.Attachment(filepath.Base(f.Name()), "data.csv")

package main

import (
	"encoding/csv"
	"errors"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strconv"

	"github.com/labstack/echo/v5"
	"github.com/labstack/echo/v5/middleware"
)

type Item struct {
	Name  string
	Price float64
	Cost  float64
}

func main() {
	e := echo.New()
	e.Filesystem = os.DirFS("/tmp")

	e.Use(middleware.RequestLogger())
	e.Use(middleware.Gzip())

	e.GET("/data.csv", func(c *echo.Context) error {

		items := []Item{
			Item{
				Name:  "Item 1",
				Price: 10.99,
				Cost:  4.63,
			},
			Item{
				Name:  "Item 2",
				Price: 20.99,
				Cost:  12.82,
			},
		}

		f, err := os.CreateTemp("/tmp/", "data-*.csv")
		if err != nil {
			e.Logger.Error("Could not create data temp file", err)
			return c.HTML(500, "Could not create data temp file")
		}
		defer f.Close()

		ic := csv.NewWriter(f)
		ic.Write([]string{
			"Name",
			"Price",
			"Cost"})
		for _, item := range items {
			row := []string{
				item.Name,
				strconv.FormatFloat(item.Price, 'f', 2, 64),
				strconv.FormatFloat(item.Cost, 'f', 3, 64)}

			ic.Write(row)
		}
		ic.Flush()

		return c.Attachment(filepath.Base(f.Name()), "data.csv")
	})

	if err := e.Start(":8080"); err != nil && !errors.Is(err, http.ErrServerClosed) {
		log.Fatal(err)
	}
}

[aldas]

note, if you set filesystem to root /. the first slash need to be removed

	e := echo.New()
	e.Filesystem = os.DirFS("/")

and

return c.Attachment(f.Name()[1:], "data.csv")

[aldas]

I will investigate if we can similar tricks with default filesystem so dir prefix would not be that big annoyance

[aldas]

@henderb I have modified defaultFS behavior so that Open can handle absolute path file names have matching prefix as filesystem. The default filesystem will still be initialized to CWD but now it easier to create fs can mimic more os.Open behavior.

so if you would change fs to, you example would work.

e.Filesystem = echo.NewDefaultFS("/tmp")

I'll release new version today

[henderb]

thanks, since I'm not sure what else might depend on the default filesystem path, I've changed my temp file creation from /tmp/ to tmp/ and it seems happy.

[aldas]

@henderb /tmp is cleaned on each restart under linux. but anyway you should not forget that files you are creating need to be removed somehow or you will run out of free space or inodes.

[henderb]

good point.

I think I'll be ok since fly.io doesn't keep files written outside mounted volumes across instance boots. Mine is scaling to zero very often. But could be a problem for later.

On dev, I'm rebuilding the container often enough or could have docker-compose map it somewhere in /tmp/my-app/