Improve B00_www_browser error reporting

[leviroth]

I tried using odig doc from WSL and got some confusing error messages:

$ odig doc base --browser="/mnt/c/Program\ Files\ \(x86\)/Google/Chrome/Application/chrome"
odig: [ERROR] show uri file:///home/leviroth/.opam/4.11.1/var/cache/odig/html/base/index.html: No browser found. Use the BROWSER env var to set one.
$ BROWSER="/mnt/c/Program\ Files\ \(x86\)/Google/Chrome/Application/chrome" odig doc base
odig: [ERROR] show uri file:///home/leviroth/.opam/4.11.1/var/cache/odig/html/base/index.html: No browser found. Use the BROWSER env var to set one.

WSL is a weird environment, so I'm not too surprised that odig wouldn't work. (Notably, odig is running on a Linux environment that lives inside a Windows environment, and has to reach back out into the Windows environment to find the browser.) However, I am surprised that the error message suggests that the BROWSER environment variable isn't set.

I poked around in the source a bit and, while I'm not sure I understood all of it, it seems like B00_www_browser.show ~background ~prefix browser uri always complains about a missing environment variable when browser is None, while in reality B00_www_browser.find might be giving us None for various other reasons.

[dbuenzli]

I poked around in the source a bit and, while I'm not sure I understood all of it, it seems like B00_www_browser.show ~background ~prefix browser uri always complains about a missing environment variable when browser is None, while in reality B00_www_browser.find might be giving us None for various other reasons.

Indeed. I suspect in this particular case the None comes from this line, that is the program lookup fails. The erroring paths (and the whole thing) should be reviewed.

If you have a toplevel at hand would you mind invoking:

# #require "b0.b00.kit";;
# open B00_std;;
# Os.Cmd.find ((Cmd.of_string "/mnt/c/Program\ Files\ \(x86\)/Google/Chrome/Application/chrome") |> Result.to_failure);;

To see what happens.

Also I love to have Windows users at hand so bear with me. Could you tell me if using:

start file:///home/leviroth/.opam/4.11.1/var/cache/odig/html/base/index.html

would do what you'd expect.

(Also if you want to make tests you can use the show-uri tool which uses the same API).

[dbuenzli]

BROWSER="/mnt/c/Program\ Files\ \(x86\)/Google/Chrome/Application/chrome"

Also since you have quotes here aren't the escaped spaces too much here ?

In the toplevel instructions above also please simply try with:

"/mnt/c/Program Files (x86)/Google/Chrome/Application/chrome"

[leviroth]

You're right, the escapes are useless. I tried both versions, and also one with .exe for good measure.

# #require "b0.b00.kit";;
/home/leviroth/.opam/4.11.1/lib/ocaml/unix.cma: loaded
/home/leviroth/.opam/4.11.1/lib/cmdliner: added to search path
/home/leviroth/.opam/4.11.1/lib/cmdliner/cmdliner.cma: loaded
/home/leviroth/.opam/4.11.1/lib/b0/b00/std: added to search path
/home/leviroth/.opam/4.11.1/lib/b0/b00/std/b00_std.cma: loaded
/home/leviroth/.opam/4.11.1/lib/b0/b00: added to search path
/home/leviroth/.opam/4.11.1/lib/b0/b00/b00.cma: loaded
/home/leviroth/.opam/4.11.1/lib/b0/b00/kit: added to search path
/home/leviroth/.opam/4.11.1/lib/b0/b00/kit/b00_kit.cma: loaded
# open B00_std;;
# Os.Cmd.find ((Cmd.of_string "/mnt/c/Program\ Files\ \(x86\)/Google/Chrome/Application/chrome") |> Result.to_failure);;
Warning 14: illegal backslash escape in string.
Warning 14: illegal backslash escape in string.
- : (B00_std.Cmd.t option, string) result = Ok None
# Os.Cmd.find ((Cmd.of_string "/mnt/c/Program Files (x86)/Google/Chrome/Application/chrome") |> Result.to_failure);;
- : (B00_std.Cmd.t option, string) result = Ok None
# Os.Cmd.find ((Cmd.of_string "/mnt/c/Program Files (x86)/Google/Chrome/Application/chrome.exe") |> Result.to_failure);;
- : (B00_std.Cmd.t option, string) result = Ok None

---

start file:///home/leviroth/.opam/4.11.1/var/cache/odig/html/base/index.html

just results in

$ start file:///home/leviroth/.opam/4.11.1/var/cache/odig/html/base/index.html

Command 'start' not found, did you mean:

  command 'rstart' from deb x11-session-utils (7.7+4)
  command 'startx' from deb xinit (1.4.1-0ubuntu2)
  command 'stat' from deb coreutils (8.30-3ubuntu2)
  command 'tart' from deb tart (3.10-1build1)

Try: sudo apt install <deb name>

So it seems like start isn't known to Ubuntu or its package manager.

[dbuenzli]

So it seems like start isn't known to Ubuntu or its package manager.

Well no that's a Windows thing which B00_www_browser should likely support.

You're right, the escapes are useless.

Actually they are not useless, Cmd.of_string, which is used on the BROWSER value parses a command line, not a tool specification. So I think this is just a matter of bad quoting:

# #install_printer Cmd.dump;;
# let cmd = Cmd.of_string "/mnt/c/Program\\ Files\\ (x86)/Google/Chrome/Application/chrome";;
val cmd : (B00_std.Cmd.t, string) result =
  Ok '/mnt/c/Program\' 'Files\' '(x86)/Google/Chrome/Application/chrome'
# let cmd = Cmd.of_string "'/mnt/c/Program Files (x86)/Google/Chrome/Application/chrome'";;
val cmd : (B00_std.Cmd.t, string) result =
  Ok '/mnt/c/Program Files (x86)/Google/Chrome/Application/chrome'

Could you please try again with the correct quoting. I'm not exactly sure who invokes what and which platform is discovered but you will likely have to add the .exe.

[leviroth]

Ah, so the following opened the browser:

$ odig doc base --browser="'/mnt/c/Program Files (x86)/Google/Chrome/Application/chrome.exe'"

But with an important caveat: Windows Chrome is trying to read the docs from a filesystem path, but it doesn't have access to the Linux filesystem. So it sees a path like file:///home/leviroth/.opam/4.11.1/var/cache/odig/html/base/index.html and comes back with a 404 error.

[dbuenzli]

Good.

But with an important caveat: Windows Chrome is trying to read the docs from a filesystem path, but it doesn't have access to the Linux filesystem.

That I'm afraid you will have to sort out yourself :-)

[MisterDA]

On Windows, I cannot set the browser to use, through the --browser flag or the BROWSER env var. I've tried both an Unix shell in Cygwin and the cmd.

$ odig doc --browser='C:\Program Files\Mozilla Firefox\firefox.exe' b0
odig.exe: [ERROR] show uri file://C:\Users\antonin\.opam\ocaml-variants.4.13.1+mingw64c\var\cache\odig\html\b0\index.html: No browser found. Use the BROWSER env var to set one.
$ odig doc --browser='C:/Program Files/Mozilla Firefox/firefox.exe' b0
odig.exe: [ERROR] show uri file://C:\Users\antonin\.opam\ocaml-variants.4.13.1+mingw64c\var\cache\odig\html\b0\index.html: No browser found. Use the BROWSER env var to set one.
$ odig doc --browser='/cygdrive/c/Program Files/Mozilla Firefox/firefox.exe' b0
odig.exe: [ERROR] show uri file://C:\Users\antonin\.opam\ocaml-variants.4.13.1+mingw64c\var\cache\odig\html\b0\index.html: No browser found. Use the BROWSER env var to set one.

Note that start is a cmd builtin, so you won't wind a start.exe. It could be invoked through Sys.command.

cmd /S /C start file://C:\Users\antonin\.opam\ocaml-variants.4.13.1+mingw64c\var\cache\odig\html\b0\index.html

and so this works:

odig doc --browser='cmd.exe /S /C start' b0

[dbuenzli]

@MisterDA

1. Maybe there is a bug in Os.Cmd.find. Could you please try to lookup these strings in the toplevel as mentioned in this this message.

2. Do you think the following logic is good: Default to cmd.exe /S /C start if Sys.win32 is true ? (What are the /S and /C for ?)

[MisterDA]

1. Maybe there is a bug in Os.Cmd.find. Could you please try to lookup these strings in the toplevel as mentioned in this this message.

utop # #require "b0.b00.kit";;
utop # open B00_std;;

utop # Os.Cmd.find ((Cmd.of_string {|C:\Program Files\Mozilla Firefox\firefox.exe|}) |> Result.to_failure);;
- : (Cmd.t option, string) result = Ok None

utop # Os.Cmd.find ((Cmd.of_string {|C:/Program Files/Mozilla Firefox/firefox.exe|}) |> Result.to_failure);;
- : (Cmd.t option, string) result = Ok None

utop # Os.Cmd.find ((Cmd.of_string {|/cygdrive/c/Program Files/Mozilla Firefox/firefox.exe|}) |> Result.to_failure);;
- : (Cmd.t option, string) result = Ok None

2. Do you think the following logic is good: Default to cmd.exe /S /C start if Sys.win32 is true ? (What are the /S and /C for ?)

Yes, I think it is good. start will use the user-defined association between URL and application. You could also call Unix.system.

if Sys.win32 then
  Unix.system({|start file://C:\Users\antonin\.opam\ocaml-variants.4.13.1+mingw64c\var\cache\odig\html\tar\index.html|})
else ...

/C is like sh -c, it executes the command given as parameter. /S strips the command of quotes, the flag is not needed here. I used it out of habit. Unofficial manual.

[dbuenzli]

@MisterDA thanks would mind having a look what in this logic makes Os.Cmd.find return None. Normally it should end up in this branch.

In particular what does Unix.access file [Unix.X_OK] say on these files ?

You could also call Unix.system.

There's too much unreliability and quoting complexity in using Unix.system, I prefer to know exactly which program I invoke with which data.

[MisterDA]

In particular what does Unix.access file [Unix.X_OK] say on these files ?

It's actually documented!

On Windows: execute permission X_OK cannot be tested, just tests for read permission instead.

I'm running these examples in Zsh in Cygwin, with opam correctly set up.

utop # Unix.access {|C:\Program Files\Mozilla Firefox\firefox.exe|} [Unix.X_OK];;
- : unit = ()

utop # Unix.access {|C:/Program Files/Mozilla Firefox/firefox.exe|} [Unix.X_OK];;
- : unit = ()

utop # Unix.access {|/cygdrive/c/Program Files/Mozilla Firefox/firefox.exe|}  [Unix.X_OK];;
Exception:
Unix.Unix_error(Unix.ENOENT, "access", "/cygdrive/c/Program Files/Mozilla Firefox/firefox.exe")

Accessing using a Cygwin path raises.
Then, I don't quite follow the logic, but I'll retry next week.

[dbuenzli]

It's actually documented!

Indeed so it should work. @MisterDA did you have time to investigate this further ?

I'd be interested in providing a good Windows default on the line of 2. above but I'd also like to fix 1. I reread the code and couldn't get what goes wrong.