No such file or directory error with ppx_expect

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I'm using `ppx_expect` to test my Reason files. In any Reason module that includes `let%expect_test` I see the following build error:

```
type error here Line 1:
Error: I/O error: : No such file or directory
```

I'm building with `esy`. When I run the tests with `esy dune runtest` everything runs just fine. This problem only effects editing _Reason_ files that use `let%expect_test` (ml files do not exhibit this issue). All other files work fine.

The entire build command from debug.log is too much to paste here, but the last part of the build command the output showing the error are:

```
{snip}
-bin-annot -open NaismithSrc -open Core_kernel -open NaismithExt.Pipe -ppx '/src/reason-playground/naismith/_esy/default/store/b/naismith-6ce4e131/default/.ppx/c71d0a51e5287292e3bae7e7566a859b/ppx.exe --as-ppx --cookie '\''library-name="NaismithSrc"'\''' -impl /src/reason-playground/naismith/_esy/default/store/b/naismith-6ce4e131/.lsp/NaismithSrc__Repl.ast with pwd /src/reason-playground/naismith/src
Now loading /src/reason-playground/naismith/_esy/default/store/b/naismith-6ce4e131/.lsp/NaismithSrc__Repl.cmt
Size 55934
<< Making lastDefinitions with type error for file:///src/reason-playground/naismith/src/Repl.re
type error here Line 1:
Error: I/O error: : No such file or directory
Sending notification {"jsonrpc": "2.0", "method": "textDocument/publishDiagnostics", "params":{"uri": "file:///src/reason-playground/naismith/src/Repl.re", "diagnostics": [{"range": {"start": {"line": 0, "character": 0}, "end": {"line": 0, "character": 0}}, "message": "Line 1:\nError: I/O error: : No such file or directory", "severity": 1}]}}
```
If it helps, here's the output of `esy ls-libs` showing installed libraries and versions:

```
naismith@0.1.0 [build pending]
├── @esy-ocaml/reason@3.6.0 [built]
│ ├── reason.easy_format
│ ├── reason.cmdliner
│ └── reason
├── @opam/alcotest@opam:1.0.0 [built]
│ └── alcotest
├── @opam/base@opam:v0.13.0 [built]
│ ├── base.shadow_stdlib
│ ├── base.md5
│ ├── base.caml
│ ├── base.base_internalhash_types
│ └── base
├── @opam/core_kernel@opam:v0.13.0 [built]
│ ├── core_kernel.weak_pointer
│ ├── core_kernel.weak_hashtbl
│ ├── core_kernel.weak_array
│ ├── core_kernel.version_util
│ ├── core_kernel.uuid
│ ├── core_kernel.uopt
│ ├── core_kernel.unpack_buffer
│ ├── core_kernel.univ
│ ├── core_kernel.tuple_pool
│ ├── core_kernel.total_map
│ ├── core_kernel.timing_wheel
│ ├── core_kernel.thread_safe_queue
│ ├── core_kernel.thread_pool_cpu_affinity
│ ├── core_kernel.sexp_hidden_in_test
│ ├── core_kernel.rope
│ ├── core_kernel.pooled_hashtbl
│ ├── core_kernel.pairing_heap
│ ├── core_kernel.moption
│ ├── core_kernel.linked_stack
│ ├── core_kernel.limiter
│ ├── core_kernel.int_set
│ ├── core_kernel.hash_heap
│ ├── core_kernel.force_once
│ ├── core_kernel.flags
│ ├── core_kernel.fheap
│ ├── core_kernel.composition_infix
│ ├── core_kernel.bounded_int_table
│ ├── core_kernel.binary_packing
│ ├── core_kernel.base_for_tests
│ ├── core_kernel.balanced_reducer
│ └── core_kernel
├── @opam/dune@opam:2.2.0 [built]
│ ├── dune.configurator
│ └── dune
├── @opam/expect_test_helpers_kernel@opam:v0.13.0 [built]
│ ├── expect_test_helpers_kernel.expect_test_helpers_base
│ └── expect_test_helpers_kernel
├── @opam/fmt@opam:0.8.8 [built]
│ ├── fmt.tty
│ ├── fmt.top
│ ├── fmt.cli
│ └── fmt
├── @opam/menhir@opam:20200123 [built]
│ └── menhir
├── @opam/merlin@opam:3.3.3 [built]
│ └── merlin
├── @opam/odoc@opam:1.5.0 [built]
│ ├── odoc.xref
│ ├── odoc.parser
│ ├── odoc.odoc
│ ├── odoc.model
│ ├── odoc.loader
│ ├── odoc.html
│ ├── odoc.compat
│ └── odoc
├── @opam/patdiff@opam:v0.13.0 [built]
│ ├── patdiff.lib
│ └── patdiff
├── @opam/ppx_deriving@opam:4.4 [built]
│ ├── ppx_deriving.std
│ ├── ppx_deriving.show
│ ├── ppx_deriving.runtime
│ ├── ppx_deriving.ord
│ ├── ppx_deriving.map
│ ├── ppx_deriving.make
│ ├── ppx_deriving.iter
│ ├── ppx_deriving.fold
│ ├── ppx_deriving.eq
│ ├── ppx_deriving.enum
│ ├── ppx_deriving.create
│ ├── ppx_deriving.api
│ └── ppx_deriving
├── @opam/ppx_expect@opam:v0.13.0 [built]
│ ├── ppx_expect.payload
│ ├── ppx_expect.matcher
│ ├── ppx_expect.evaluator
│ ├── ppx_expect.config
│ ├── ppx_expect.common
│ ├── ppx_expect.collector
│ └── ppx_expect
├── @opam/rtop@opam:3.5.2 [built]
│ └── rtop
├── @opam/sedlex@opam:2.1 [built]
│ ├── sedlex.ppx
│ └── sedlex
├── @opam/stdio@opam:v0.13.0 [built]
│ └── stdio
├── @pesy/esy-pesy@0.1.0-alpha.5 [built]
│ ├── pesy--esy-pesy.utils
│ ├── pesy--esy-pesy.lib
│ ├── pesy--esy-pesy.errors
│ └── pesy--esy-pesy
├── @reason-native/console@0.1.0 [built]
│ ├── console.lib
│ └── console
├── @reason-native/pastel@0.3.0 [built]
│ ├── pastel.lib
│ ├── pastel.internal
│ └── pastel
├── @reason-native/rely@3.2.1 [built]
│ ├── rely.lib
│ ├── rely.internal
│ └── rely
├── ocaml@4.8.1000 [built]
└── refmterr@3.3.0 [built]
├── refmterr.lib
└── refmterr
```

Reproduziere den Fehler, indem du eine Reason-Datei bearbeitest, die `let%expect_test` enthält, mit dem im Bericht angegebenen esy-Setup, und vergleiche die Editor-Diagnosen mit `esy dune runtest`. Verfolge den im Bericht gezeigten Build-Befehl des Language Servers und seinen `ppx_expect`-Aufruf. Als erledigt gilt die Aufgabe, wenn Reason-Dateien die I/O-Diagnose nicht mehr erhalten und der bestehende Testbefehl weiterhin erfolgreich ist.

Vom Indexierungsmodell aus dem Issue-Text verfasst.