Improve filesystem support

[aldas]

Improve filesystem support. Relates to #2059 I have taken some code from v5 and made it v4 compatible

Usable if you have Go 1.16+, older Go versions will use old implementation

• Add field echo.Filesystem, default filesystem that is set on echo.New() emulates how previously os.Open worked
• Add methods:
  • echo.FileFS(path, file string, filesystem fs.FS, m ...MiddlewareFunc),
  • echo.StaticFS(pathPrefix string, fileSystem fs.FS),
  • group.FileFS(path, file string, filesystem fs.FS, m ...MiddlewareFunc),
  • group.StaticFS(pathPrefix string, fileSystem fs.FS).
  • MustSubFS(currentFs fs.FS, fsRoot string) fs.FS
• Following methods will use internally echo.Filesystem to serve files:
  • echo.File,
  • echo.Static,
  • group.File,
  • group.Static,
  • Context.File

Note: embed.FS embedds files with full paths that include that same embedded directory name as prefix. In that case you can use helper function to create sub fs with that prefix echo.MustSubFS(embedded, rootDirectory). That "root prefix" was not added to the method signature as there could be fs.FS implementations that do not act that way.

Example with embed.FS:

//go:embed testdata
var embedded embed.FS

// assuming we have directory structure
// ./  <- execution dir
// ./testdata/  <- directory we are embedding
// ./testdata/index.html   <- on of the embedded files

func main() {
	e := echo.New()

	e.Use(middleware.Logger())
	e.Use(middleware.Recover())

	e.StaticFS("/assets", echo.MustSubFS(embedded, "testdata"))

	log.Fatal(e.Start(":8080"))
}

[aldas]

well well, I forgot already that fs.FS was introduced in Go 1.16. If echo.Filesystem part is removed and only *FS methods are left this could be made work with build tags for Go 1.16+.

[lammel]

well well, I forgot already that fs.FS was introduced in Go 1.16. If echo.Filesystem part is removed and only *FS methods are left this could be made work with build tags for Go 1.16+.

I'd suggest we tag this PR as v5 and merge on the v5 branch where Go < 1.16 is dropped, so we can use fs.FS directly from Go. What do you think @aldas ?

[aldas]

There is not point tag it as v5 as most of it is taken from v5 branch.

I can make it work with Go 1.16+ versions with build constraints. I would create additional struct to be embedded into echo.Echo struct in separate file along with those fs.FS related stuff and create version for pre and after 1.16+

Add it to echo.Echo along with common

echo/echo.go

Lines 68 to 70 in 296c313

	Echo struct {
	common
	// startupMutex is mutex to lock Echo instance access during server configuration and startup. Useful for to get

and create version specific implementations in that versioned file

// +build go1.16

type versioned struct {
	Filesystem fs.FS
}

// ... methods requiring fs.FS interface

// +build !go1.16
type versioned struct {}

[lammel]

I can make it work with Go 1.16+ versions with build constraints. I would create additional struct to be embedded into echo.Echo struct in separate file along with those fs.FS related stuff and create version for pre and after 1.16+

If it is not too much effort, great. Than we can merge it for v4.6. Lovely!

[codecov]

Codecov Report

Merging #2064 (2f39f09) into master (6f6befe) will increase coverage by 0.18%.
The diff coverage is 92.40%.

@@            Coverage Diff             @@
##           master    #2064      +/-   ##
==========================================
+ Coverage   91.57%   91.76%   +0.18%     
==========================================
  Files          33       36       +3     
  Lines        2921     2962      +41     
==========================================
+ Hits         2675     2718      +43     
+ Misses        157      156       -1     
+ Partials       89       88       -1     

Impacted Files	Coverage Δ
context.go	88.04% <ø> (+1.10%)	⬆️
group.go	100.00% <ø> (ø)
context_fs_go1.16.go	80.00% <80.00%> (ø)
echo_fs_go1.16.go	95.83% <95.83%> (ø)
echo.go	95.14% <100.00%> (+0.93%)	⬆️
group_fs_go1.16.go	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6f6befe...2f39f09. Read the comment docs.

[aldas]

Ok, this should be done now. Added some tweaks for easier usage with embed.FS. Note: there are no embed.FS in tests as then go.mod should be bumped to go1.16.

Please review @lammel

[aldas]

bump @lammel

[lammel]

bump @lammel

Bump noted ;-) Checking now...

[lammel]

Reviewed all files, LGTM. Very nice stuff to support Go 1.16 too.

[jxsl13]

I think the behavior of e.Static() changed due to this update.
I did upgrade from the latest 4.6 version to 4.7 which broke my Static file downloads.

before

e.Static("/static", staticDir)

seems not to work the way it did in 4.6.x, as I do get HTTP 404 errors instead of the files above.

after

e.StaticFS("/static", os.DirFS(staticDir))

[aldas]

@jxsl13 are you using relative paths as staticDir? Are those out of CWD (current working directory) directory structure?

And let me clarify.

a) This line e.Static("/static", staticDir) does not work as it worked before?
b) or e.Static("/static", staticDir) and e.StaticFS("/static", os.DirFS(staticDir)) does not seem to be functionally equivalent?

[jxsl13]

@aldas
b) is functionally equivalent
a) does not work as it did work before 4.7

sorry for the late reply

I am constructing an absolute path from os.Getwd + some subdirectories. So staticDir is an absolute path

[aldas]

@jxsl13 please try v4.7.1 it should be better now - hopefully.

[jxsl13]

@aldas it does work again.

[jxsl13]

State in 4.7.1:
a) does work as it did work before 4.7
AND
b) is functionally equivalent

[aldas]

nice.

for history sake: os.DirFs.Open() considers paths that start with ./, ../ and / as invalid.