So I have my server set up very simply. If the path is of the form /article/something, it should serve up the static file something.html within the folder static. For some reason, the Files.file webpart is apparently returning None. I tacked on the OK "File Displayed" webpart to verify that this is the case. The OK never executes.
let app =
choose [
pathScan "/article/%s" (fun article ->
let name = sprintf "%s.html" article
Console.WriteLine name
Files.file name >=> OK "File Displayed")
]
let config =
{ defaultConfig with homeFolder = Some (Path.GetFullPath "./static") }
[<EntryPoint>]
let main args =
startWebServer config app
0
Interestingly enough, the Console.WriteLine name line executes perfectly and I see something.html in the console window when I execute this. It appears the problem is exclusively Files.file name returning None.
The file something.html definitely exists in the static folder, so that's not the problem .
Any ideas on what might be causing this?
Here are some parts to troubleshoot static file serving issues
let troubleShootExtensionPart extensionToCheck :WebPart =
fun ctx ->
match extensionToCheck with
| null | "" -> ServerErrors.INTERNAL_ERROR "Extension Error not supplied, part is not set up correctly"
| x when not <| x.StartsWith "." -> ServerErrors.INTERNAL_ERROR "Extensions start with a '.', part is not set up correctly"
| _ ->
let mtm = ctx.runtime.mimeTypesMap
match mtm extensionToCheck with
| None ->
sprintf "%s is not supported by the mime types map, compose your mime type with the `defaultMimeTypesMap`" extensionToCheck
|> RequestErrors.FORBIDDEN
| Some x ->
sprintf "%s is supported and uses '%s', compression on? : %A" extensionToCheck x.name x.compression
|> OK
|> fun wp -> wp ctx
example consumption with a wildcard so if no routes match you get some diagnostic info
#if DEBUG
pathScan "/checkExtension/%s" (fun name -> troubleShootExtensionPart name)
// catch all
(fun ctx -> sprintf "404, also homeFolder resolves to %s" (Path.GetFullPath ".") |> RequestErrors.NOT_FOUND |> fun wp -> wp ctx)
#endif
Related
Suppose I have a test like this:
module MyTests
open Xunit
open FParsec
open FsUnit.Xunit
open MyParsers
[<Fact>]
let ``pfoo works as expected`` () =
let text = "blahblahblah"
let actual =
match run pfoo text with
| Success (x, _, _) -> Result.Ok x
| Failure (s, _, _) -> Result.Error s
let expected : Result<Foo, string> =
Result.Ok
{
Foo = "blahblahblah"
}
expected
|> should equal actual
open FParsec will shadow Ok so that I need to fully qualify it like Result.Ok.
This is pretty annoying. Is there a good way to "open" Result again so that I can write Ok unqualified?
It's not Result that you need to "open", but Microsoft.FSharp.Core, which is the module in which Result and both its constructors are defined. This module is open by default, but you can open it again to have its definitions closer in the scope:
open Xunit
open FParsec
open FsUnit.Xunit
open MyParsers
open Microsoft.FSharp.Core
Alternatively, you can alias just the Ok identifier:
let Ok = Result.Ok
let x = Ok "foo" // x : Result<string, _>
I prefer this latter method, because it minimizes the impact surface and thus reduces the chance of unexpected surprises.
The downside is that the aliased Ok won't work for pattern matching:
match x with
| Ok y -> ... // This is Ok from FParsec
If you need pattern matching as well, you'll have to alias the matcher too:
let (|Ok|Error|) x = match x with | Result.Ok o -> Ok o | Result.Error e -> Error e
At which point I would probably fall back to reopening the module.
Say I have a a function
let GetDataFromWebsite (url:string) =
let webpage = HtmlDocument.Load(url)
let html = webpage.TryGetHtml
html
(note that this will become a longer function once I work out how to use the TryGetHtml function)
This tells me that it has a return string -> unit -> HtmlNode option. What is this exactly returning and how do I use it? I have tried
match GetDataFromWebsite(#"...") with
| None -> "None"
| _ -> (fun a -> a.ToString())
|> printfn "%s"
but visual studio states that:
This expresion was expected to have type
'unit -> FSharp.Data.HtmlNode option'
but here has type
''a option'
Nearly there :)
TryGetHtml is a function, not a property, and you likely want to evaluate it instead of assigning it:
let GetDataFromWebsite (url:string) =
let webpage = HtmlDocument.Load(url)
let html = webpage.TryGetHtml() // note braces
html
Now it returns HtmlNode option you can pattern match on:
match GetDataFromWebsite(#"...") with
| None -> "None"
| Some x -> x.ToString()
|> printfn "%s"
This should compile without errors.
try (box (Directory.GetDirectories(dir) ))
with | :? System.UnauthorizedAccessException -> ()
I'm trying to check if the directory is accessible so I won't get an "access denied" error, but it's not working, it's not skipping the loop in for
It's generally discouraged to use exceptions as part of your control flow. It's better to check for the appropriate access to the directory before trying to enumerate its contents. Try something like this:
open System
open System.IO
open System.Linq
open System.Security.AccessControl
open System.Security.Principal
let checkSecurity =
let account = sprintf #"%s\%s" Environment.UserDomainName Environment.UserName
let identity = WindowsIdentity.GetCurrent()
let principal = identity |> WindowsPrincipal
let isAdmin = identity.Owner = identity.User
fun (dir: DirectoryInfo) ->
try
let acl = dir.GetAccessControl(AccessControlSections.All)
let rules = acl.GetAccessRules(true, true, typeof<NTAccount>)
rules.OfType<FileSystemAccessRule>()
|> Seq.filter (fun rule -> rule.IdentityReference.Value.Equals(account, StringComparison.CurrentCultureIgnoreCase) ||
(if rule.IdentityReference.Value.Equals("BUILTIN\Administrators", StringComparison.CurrentCultureIgnoreCase)
then isAdmin && principal.IsInRole(rule.IdentityReference.Value)
else principal.IsInRole(rule.IdentityReference.Value)))
|> Seq.exists (fun rule -> (rule.FileSystemRights &&& FileSystemRights.Read = FileSystemRights.Read) && rule.AccessControlType <> AccessControlType.Deny)
with | _ ->
false
let rec getFiles (dir: DirectoryInfo) =
[ if checkSecurity dir
then for file in dir.GetFiles("*") do yield file
for subDir in dir.GetDirectories("*") do yield! getFiles subDir
]
let dir = DirectoryInfo(#"C:\Temp")
dir |> getFiles
You might have some other issues, if you have an exception the try-with block should be able to handle it, so either you're actually not getting an exception or have some other issues in the surrounding code. Why do you box?
The aversion to using exceptions as control flow makes some sense in .NET. in OCaml exceptions are used extensively for that purpose, but they are cheap. In .NET this is more expensive in performance terms. That said, sometimes you do want catch and handle an exception, so I don't think it's such a big issue. This for example works:
open System.IO
let okdir = #"c:\tmp"
let baddir = #"L:\Finance"
let checkDir dir =
try
Directory.GetDirectories(dir) |> ignore
printfn "%A" "Processed"
with
| :? System.UnauthorizedAccessException as ex -> failwith ex.Message
| :? System.IO.IOException as ex -> failwith ex.Message
// | :? System.Exception as ex -> failwith ex.Message
checkDir okdir
//"Processed"
//val it : unit = ()
checkDir baddir
//System.Exception: Access to the path 'L:\Finance' is denied.
I created a "Game" class and i'm trying to use values from my webpart path to create an instance of it.
My instance need a playerName so i tried to create one with the name value
let g:game.Game = new game.Game()
let php =
request (fun r ->
match r.queryParam "playerName" with
| Choice1Of2 name -> new game.Game(1,name,"hyy")//OK (sprintf "playerName: %s" name)
| Choice2Of2 msg -> BAD_REQUEST msg)
let webPart =
choose [
path "/" >=> (OK "Home")
path "/elm/api/create.php" >=> php
]
startWebServer defaultConfig webPart
but it doesn't work because this expression is supposed to be HttpContext type and not Game type.
I'd like to create an instance and call class's methods depending on my path values.
first: you cant return 2 different types from your function
let php =
request (fun r ->
match r.queryParam "playerName" with
| Choice1Of2 name -> new game.Game(1,name,"hyy")
^^^^^^^^^^^
//should probably be a OK
//OK (sprintf "playerName: %s" name)
| Choice2Of2 msg -> BAD_REQUEST msg)
Then you also should Jsonify your Game object. So probably your code should look somehow like this
| Choice1Of2 name ->
new game.Game(1,name,"hyy")
|> toJson
|> OK
please substitute toJson with a call of your chosen Json library
First let me apologize for the scale of this problem but I'm really trying to think functionally and this is one of the more challenging problems I have had to work with.
I wanted to get some suggestions on how I might handle a problem I have in a functional manner, particularly in F#. I am writing a program to go through a list of directories and using a list of regex patterns to filter the list of files retrieved from the directories and using a second list of regex patterns to find matches in the text of the retreived files. I want this thing to return the filename, line index, column index, pattern and matched value for each piece of text that matches a given regex pattern. Also, exceptions need to be recorded and there are 3 possible exceptions scenarios: can't open the directory, can't open the file, reading content from the file failed. The final requirement of this is the the volume of files "scanned" for matches could be very large so this whole thing needs to be lazy. I'm not too worried about a "pure" functional solution as much as I'm interested in a "good" solution that reads well and performs well. One final challenge is to make it interop with C# because I would like to use the winform tools to attach this algorithm to a ui. Here is my first attempt and hopefully this will clarify the problem:
open System.Text.RegularExpressions
open System.IO
type Reader<'t, 'a> = 't -> 'a //=M['a], result varies
let returnM x _ = x
let map f m = fun t -> t |> m |> f
let apply f m = fun t -> t |> m |> (t |> f)
let bind f m = fun t -> t |> (t |> m |> f)
let Scanner dirs =
returnM dirs
|> apply (fun dirExHandler ->
Seq.collect (fun directory ->
try
Directory.GetFiles(directory, "*", SearchOption.AllDirectories)
with | e ->
dirExHandler e directory
Array.empty))
|> map (fun filenames ->
returnM filenames
|> apply (fun (filenamepatterns, lineExHandler, fileExHandler) ->
Seq.filter (fun filename ->
filenamepatterns |> Seq.exists (fun pattern ->
let regex = new Regex(pattern)
regex.IsMatch(filename)))
>> Seq.map (fun filename ->
let fileinfo = new FileInfo(filename)
try
use reader = fileinfo.OpenText()
Seq.unfold (fun ((reader : StreamReader), index) ->
if not reader.EndOfStream then
try
let line = reader.ReadLine()
Some((line, index), (reader, index + 1))
with | e ->
lineExHandler e filename index
None
else
None) (reader, 0)
|> (fun lines -> (filename, lines))
with | e ->
fileExHandler e filename
(filename, Seq.empty))
>> (fun files ->
returnM files
|> apply (fun contentpatterns ->
Seq.collect (fun file ->
let filename, lines = file
lines |>
Seq.collect (fun line ->
let content, index = line
contentpatterns
|> Seq.collect (fun pattern ->
let regex = new Regex(pattern)
regex.Matches(content)
|> (Seq.cast<Match>
>> Seq.map (fun contentmatch ->
(filename,
index,
contentmatch.Index,
pattern,
contentmatch.Value))))))))))
Thanks for any input.
Updated -- here is any updated solution based on feedback I received:
open System.Text.RegularExpressions
open System.IO
type ScannerConfiguration = {
FileNamePatterns : seq<string>
ContentPatterns : seq<string>
FileExceptionHandler : exn -> string -> unit
LineExceptionHandler : exn -> string -> int -> unit
DirectoryExceptionHandler : exn -> string -> unit }
let scanner specifiedDirectories (configuration : ScannerConfiguration) = seq {
let ToCachedRegexList = Seq.map (fun pattern -> new Regex(pattern)) >> Seq.cache
let contentRegexes = configuration.ContentPatterns |> ToCachedRegexList
let filenameRegexes = configuration.FileNamePatterns |> ToCachedRegexList
let getLines exHandler reader =
Seq.unfold (fun ((reader : StreamReader), index) ->
if not reader.EndOfStream then
try
let line = reader.ReadLine()
Some((line, index), (reader, index + 1))
with | e -> exHandler e index; None
else
None) (reader, 0)
for specifiedDirectory in specifiedDirectories do
let files =
try Directory.GetFiles(specifiedDirectory, "*", SearchOption.AllDirectories)
with e -> configuration.DirectoryExceptionHandler e specifiedDirectory; [||]
for file in files do
if filenameRegexes |> Seq.exists (fun (regex : Regex) -> regex.IsMatch(file)) then
let lines =
let fileinfo = new FileInfo(file)
try
use reader = fileinfo.OpenText()
reader |> getLines (fun e index -> configuration.LineExceptionHandler e file index)
with | e -> configuration.FileExceptionHandler e file; Seq.empty
for line in lines do
let content, index = line
for contentregex in contentRegexes do
for mmatch in content |> contentregex.Matches do
yield (file, index, mmatch.Index, contentregex.ToString(), mmatch.Value) }
Again, any input is welcome.
I think that the best approach is to start with the simplest solution and then extend it. Your current approach seems to be quite hard to read to me for two reasons:
The code uses a lot of combinators and function compositions in patterns that are not too common in F#. Some of the processing can be more easily written using sequence expressions.
The code is all written as a single function, but it is fairly complex and would be more readable if it was separated into multiple functions.
I would probably start by splitting the code in a function that tests a single file (say fileMatches) and a function that walks over the files and calls fileMatches. The main iteration can be quite nicely written using F# sequence expressions:
// Checks whether a file name matches a filename pattern
// and a content matches a content pattern.
let fileMatches fileNamePatterns contentPatterns
(fileExHandler, lineExHandler) file =
// TODO: This can be imlemented using
// File.ReadLines which returns a sequence.
// Iterates over all the files and calls 'fileMatches'.
let scanner specifiedDirectories fileNamePatterns contentPatterns
(dirExHandler, fileExHandler, lineExHandler) = seq {
// Iterate over all the specified directories.
for specifiedDir in specifiedDirectories do
// Find all files in the directories (and handle exceptions).
let files =
try Directory.GetFiles(specifiedDir, "*", SearchOption.AllDirectories)
with e -> dirExHandler e specifiedDir; [||]
// Iterate over all files and report those that match.
for file in files do
if fileMatches fileNamePatterns contentPatterns
(fileExHandler, lineExHandler) file then
// Matches! Return this file as part of the result.
yield file }
The function is still quite complicated, because you need to pass a lot of parameters around. Wrapping the parameters in a simple type or a record could be a good idea:
type ScannerArguments =
{ FileNamePatterns:string
ContentPatterns:string
FileExceptionHandler:exn -> string -> unit
LineExceptionHandler:exn -> string -> unit
DirectoryExceptionHandler:exn -> string -> unit }
Then you can define both fileMatches and scanner as functions that take just two parameters, which will make your code a lot more readable. Something like:
// Iterates over all the files and calls 'fileMatches'.
let scanner specifiedDirectories (args:ScannerArguments) = seq {
for specifiedDir in specifiedDirectories do
let files =
try Directory.GetFiles(specifiedDir, "*", SearchOption.AllDirectories)
with e -> args.DirectoryExceptionHandler e specifiedDir; [||]
for file in files do
// No need to propagate all arguments explicitly to other functions.
if fileMatches args file then yield file }