When advising user to file a bug, should mention the file it was trying to format

[penelope99]

I've tried to format a whole solution with --recurse, and received several errors of this type:

The following exception occurs while formatting stdin: System.Exception: Fantomas is trying to format the input multiple times due to the detect of multiple defines.
There is a problem with merging all the code back togheter. Please raise an issue at https://github.com/fsprojects/fantomas/issues.
   at Microsoft.FSharp.Core.PrintfModule.PrintFormatToStringThenFail@1637.Invoke(String message) in E:\A\_work\130\s\src\fsharp\FSharp.Core\printf.fs:line 1637
   at Fantomas.String.merge(String a, String b) in /home/runner/work/fantomas/fantomas/src/Fantomas/Utils.fs:line 62
   at Fantomas.CodeFormatterImpl.merged@418.Invoke(String a, String b) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodeFormatterImpl.fs:line 418
   at Microsoft.FSharp.Collections.ListModule.Fold[T,TState](FSharpFunc`2 folder, TState state, FSharpList`1 list) in E:\A\_work\130\s\src\fsharp\FSharp.Core\list.fs:line 221
   at Microsoft.FSharp.Collections.ListModule.Reduce[T](FSharpFunc`2 reduction, FSharpList`1 list) in E:\A\_work\130\s\src\fsharp\FSharp.Core\list.fs:line 232
   at Fantomas.CodeFormatterImpl.format@408-1.Invoke(Tuple`2[] _arg1) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodeFormatterImpl.fs:line 418
   at Microsoft.FSharp.Control.AsyncPrimitives.CallThenInvokeNoHijackCheck[a,b](AsyncActivation`1 ctxt, FSharpFunc`2 userCode, b result1) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 417
   at Microsoft.FSharp.Control.Trampoline.Execute(FSharpFunc`2 firstAction) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 109
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.FSharp.Control.AsyncResult`1.Commit() in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 350
   at Microsoft.FSharp.Control.AsyncPrimitives.RunSynchronouslyInCurrentThread[a](CancellationToken cancellationToken, FSharpAsync`1 computation) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 882
   at Microsoft.FSharp.Control.AsyncPrimitives.RunSynchronously[T](CancellationToken cancellationToken, FSharpAsync`1 computation, FSharpOption`1 timeout) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 890
   at Microsoft.FSharp.Control.FSharpAsync.RunSynchronously[T](FSharpAsync`1 computation, FSharpOption`1 timeout, FSharpOption`1 cancellationToken) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 1154
   at Program.processSourceString(Boolean isFsiFile, String s, FSharpChoice`2 tw, FormatConfig config) in /home/runner/work/fantomas/fantomas/src/Fantomas.CoreGlobalTool/Program.fs:line 96
   at Program.stringToFile@303(Boolean force, Boolean profile, String s, String outFile, FormatConfig config) in /home/runner/work/fantomas/fantomas/src/Fantomas.CoreGlobalTool/Program.fs:line 311

This error message should include the file name or file path that it was trying to format, so that I can report an issue with better context, I assume.

$ fantomas --version
Fantomas v3.3.0.100

[nojaf]

Hello @penelope99, thanks for reporting this.
This is something we actually are aware of, but it never really got writing down until now 😅.

We should definitely tell the user what file caused the problem.
@lpedrosa didn't you have any strategy for this in mind?
If so could you write it down here in the issue?
That way we can label this issue as up for grabs.
Anyone with a bit of F# knowledge should be able to pick this up.

[lpedrosa]

I believe this is happening because of the way errors are reported in the CLI.

One of these functions gets called, depending on the CLIs input

• with the code input coming through stdin
• with the code input being a file
• with the code input being a folder (i.e. set of files)

@penelope99 tried to recursively format a directory while formatting the files in place, rather then storing the formatted copy somewhere else (i.e. no --out parameter).

The bug might be in this branch of the else case, because the stringToFile function will report errors just like in the example posted by @penelope99 i.e. "The following exception occurs while formatting stdin:" (see here).

Some approaches to solve this problem:

• Separate the CLI format error reporting from the input processing, in similar way to how it's done in the check command or;
• Add filename information to the message by altering CodeFormatterImpl.format function

Regarding the second approach, that exception is being thrown by the Fantomas.Utils.String module. That function doesn't have any information about the file that it is processing and IMO shouldn't. Thus why you could add it in it's caller (the CodeFormatterImpl.format).

I hope this helps.

[penelope99]

Another instance of this same problem:

The following exception occurs while formatting stdin: System.Exception: cannot determine if synExpr DotGet
  (App
     (Atomic,false,Ident Baz,
      Const (Unit,/tmp.fsx (262,51--262,53) IsSynthetic=false),
      /tmp.fsx (262,31--262,53) IsSynthetic=false),
   /tmp.fsx (262,53--262,54) IsSynthetic=false,LongIdentWithDots ([OfType],[]),
   /tmp.fsx (262,31--262,60) IsSynthetic=false) is uppercase or lowercase
   at Microsoft.FSharp.Core.PrintfModule.PrintFormatToStringThenFail@1637.Invoke(String message) in E:\A\_work\130\s\src\fsharp\FSharp.Core\printf.fs:line 1637
   at Fantomas.CodePrinter.addSpaceBeforeParensInFunCall(SynExpr functionOrMethod, SynExpr arg, Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 52
   at Fantomas.CodePrinter.genExpr@1084-231.Invoke(Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 1086
   at Fantomas.CodePrinter.genTrivia@2481-1.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 2481
   at Fantomas.CodePrinter.genExpr@913-111.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 913
   at Fantomas.Context.atIndentLevel@192-6.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/Context.fs:line 192
   at Fantomas.Context.atIndentLevel(Boolean alsoSetIndent, Int32 level, FSharpFunc`2 f, Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/Context.fs:line 188
   at Fantomas.CodePrinter.genTrivia@2481-1.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 2481
   at Fantomas.CodePrinter.genExpr@918-118.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 918
   at Fantomas.CodePrinter.genTrivia@2481-1.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 2481
   at Fantomas.Context.autoNlnCheck[a](FSharpFunc`2 f, FSharpFunc`2 sep, Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/Context.fs:line 424
   at Fantomas.Context.autoNlnOrAddSep(FSharpFunc`2 f, FSharpFunc`2 sep, Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/Context.fs:line 456
   at Fantomas.CodePrinter.genExpr@1094-242.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 1094
   at Fantomas.Context.atIndentLevel@192-6.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/Context.fs:line 192
   at Fantomas.Context.atIndentLevel(Boolean alsoSetIndent, Int32 level, FSharpFunc`2 f, Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/Context.fs:line 188
   at Fantomas.CodePrinter.genTrivia@2481-1.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 2481
   at Fantomas.CodePrinter.breakNlnOrAddSpace@445-4.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 445
   at Fantomas.CodePrinter.genTrivia@2481-1.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 2481
   at Fantomas.CodePrinter.genExpr@1132-261.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 1132
   at Fantomas.CodePrinter.genExpr@1132-262.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 1132
   at Fantomas.Context.atIndentLevel@192-6.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/Context.fs:line 192
   at Fantomas.Context.atIndentLevel(Boolean alsoSetIndent, Int32 level, FSharpFunc`2 f, Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/Context.fs:line 188
   at Fantomas.CodePrinter.genTrivia@2481-1.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 2481
   at Fantomas.Context.futureNlnCheckMem(FSharpFunc`2 f, Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/Context.fs:line 429
   at Fantomas.Context.futureNlnCheck(FSharpFunc`2 f, Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/Context.fs:line 433
   at Fantomas.CodePrinter.genExprSepEqPrependType(FSharpFunc`2 genPat, ASTContext astContext, FSharpFunc`2 prefix, SynPat pat, SynExpr e, Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 469
   at Fantomas.CodePrinter.genTrivia@2481-1.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 2481
   at Fantomas.CodePrinter.genTrivia@2481-1.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 2481
   at Fantomas.Context.colEx[T](FSharpFunc`2 f', IEnumerable`1 c, FSharpFunc`2 f, Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/Context.fs:line 299
   at Fantomas.CodePrinter.sepXs@246-2.Invoke(FSharpList`1 c, FSharpFunc`2 f, Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 246
   at Fantomas.CodePrinter.genModuleDeclList@252-16.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 252
   at Fantomas.CodePrinter.genModuleDeclList@252-17.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 252
   at Fantomas.CodePrinter.genModuleDecl@344-46.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 344
   at Fantomas.CodePrinter.genTrivia@2481-1.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 2481
   at Fantomas.CodePrinter.genTrivia@2481-1.Invoke(Context x) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 2481
   at Fantomas.Context.col[T](FSharpFunc`2 f', IEnumerable`1 c, FSharpFunc`2 f, Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/Context.fs:line 289
   at Fantomas.CodePrinter.genImpFile@90-6.Invoke(Context ctx) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodePrinter.fs:line 90
   at Fantomas.CodeFormatterImpl.formatWith(ParsedInput ast, FSharpList`1 defines, FormatContext formatContext, FormatConfig config) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodeFormatterImpl.fs:line 392
   at Fantomas.CodeFormatterImpl.format@408-1.Invoke(Tuple`2[] _arg1) in /home/runner/work/fantomas/fantomas/src/Fantomas/CodeFormatterImpl.fs:line 410
   at Microsoft.FSharp.Control.AsyncPrimitives.CallThenInvokeNoHijackCheck[a,b](AsyncActivation`1 ctxt, FSharpFunc`2 userCode, b result1) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 417
   at Microsoft.FSharp.Control.Trampoline.Execute(FSharpFunc`2 firstAction) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 109
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.FSharp.Control.AsyncResult`1.Commit() in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 350
   at Microsoft.FSharp.Control.AsyncPrimitives.RunSynchronouslyInCurrentThread[a](CancellationToken cancellationToken, FSharpAsync`1 computation) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 882
   at Microsoft.FSharp.Control.AsyncPrimitives.RunSynchronously[T](CancellationToken cancellationToken, FSharpAsync`1 computation, FSharpOption`1 timeout) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 890
   at Microsoft.FSharp.Control.FSharpAsync.RunSynchronously[T](FSharpAsync`1 computation, FSharpOption`1 timeout, FSharpOption`1 cancellationToken) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 1154
   at Program.processSourceString(Boolean isFsiFile, String s, FSharpChoice`2 tw, FormatConfig config) in /home/runner/work/fantomas/fantomas/src/Fantomas.CoreGlobalTool/Program.fs:line 96
   at Program.stringToFile@303(Boolean force, Boolean profile, String s, String outFile, FormatConfig config) in /home/runner/work/fantomas/fantomas/src/Fantomas.CoreGlobalTool/Program.fs:line 311

[nojaf]

@penelope99 , that last one might be unrelated to the CLI input.
Could you maybe try and format that file in our online tool? If it fails there, please click the create issue link at the bottom.

[penelope99]

"That file"? But I still don't know what files are failing.

[nojaf]

Oh, sorry, I though I mentioned this already.
I believe Fantomas will process a folder alphabetically so given the following example:

The first time my three files a,b and c were formatted correctly and the second time I added an error in b. Nevertheless you can still see that .\a.fs was written, so it somewhat vaguely indicates that b.fs has a problem.
Bad UX nonetheless of course.