crashes when typing Elixir in an new, unsaved file set to Elixir language

[simonmcconnell]

Environment

• Elixir & Erlang versions (elixir --version): 1.14.5 & 25.3.2.2
• Elixir Language Server version: 0.15.1
• Operating system: Debian 12 (remoted in from Windows 11 using the built in remote development)
• Editor or IDE name (e.g. Emacs/VSCode): VSCode
• Editor Plugin/LSP Client name and version: 0.15.1

Running /home/cmo/.vscode-server/extensions/jakebecker.elixir-ls-0.15.1/elixir-ls-release/launch.sh
Looking for ASDF install in /home/cmo/.asdf/asdf.sh
ASDF found, relaunching in bash shell
Looking for ASDF install in /home/cmo/.asdf/asdf.sh
Sourcing ASDF
Installing ElixirLS release v0.15.0
Running in /home/cmo/app
Install complete
[Info  - 3:05:16 pm] Started ElixirLS v0.15.0
[Info  - 3:05:16 pm] Running in /home/cmo/app
[Info  - 3:05:16 pm] ElixirLS built with elixir "1.14.5" on OTP "25"
[Info  - 3:05:16 pm] Running on elixir "1.14.5 (compiled with Erlang/OTP 25)" on OTP "25"
[Info  - 3:05:17 pm] Protocols are not consolidated
[Info  - 3:05:17 pm] Elixir sources not found (checking in /home/build/elixir). Code navigation to Elixir modules disabled.
dets: file "/home/cmo/app/.elixir_ls/calls.dets" not properly closed, repairing ...
[Info  - 3:05:19 pm] Loaded DETS databases in 420ms
[Info  - 3:05:19 pm] Starting build with MIX_ENV: test MIX_TARGET: host

Current behavior

I was working on my project, created a new file with ctrl+n, changed the Language Mode for the file to Elixir, formatted it. When I type some code in, the completion backend seems to crash ElixirLS.

[Error - 2:56:49 pm] GenServer ElixirLS.LanguageServer.Server terminating
** (FunctionClauseError) no function clause matching in ElixirLS.LanguageServer.SourceFile.formatter_for/2
    (language_server 0.15.0) lib/language_server/source_file.ex:236: ElixirLS.LanguageServer.SourceFile.formatter_for("untitled:Untitled-1", "/home/cmo/app")
    (language_server 0.15.0) lib/language_server/server.ex:709: ElixirLS.LanguageServer.Server.handle_request/2
    (language_server 0.15.0) lib/language_server/server.ex:518: ElixirLS.LanguageServer.Server.handle_request_packet/3
    (language_server 0.15.0) lib/language_server/server.ex:176: ElixirLS.LanguageServer.Server.handle_cast/2
    (stdlib 4.3.1.1) gen_server.erl:1123: :gen_server.try_dispatch/4
    (stdlib 4.3.1.1) gen_server.erl:1200: :gen_server.handle_msg/6
    (stdlib 4.3.1.1) proc_lib.erl:240: :proc_lib.init_p_do_apply/3
Last message: {:"$gen_cast", {:receive_packet, %{"id" => 1271, "jsonrpc" => "2.0", "method" => "textDocument/completion", "params" => %{"context" => %{"triggerCharacter" => "@", "triggerKind" => 2}, "position" => %{"character" => 25, "line" => 2}, "textDocument" => %{"uri" => "untitled:Untitled-1"}}}}}
State: %ElixirLS.LanguageServer.Server{server_instance_id: "XdedLIjKKjdzCpUaSJ7ZyvLPnyZl4sAc", build_ref: #Reference<0.1115380041.1547436033.78918>, dialyzer_sup: #PID<0.326.0>, client_capabilities: %{"general" => %{"markdown" => %{"parser" => "marked", "version" => "1.1.0"}, "positionEncodings" => ["utf-16"], "regularExpressions" => %{"engine" => "ECMAScript", "version" => "ES2020"}, "staleRequestSupport" => %{"cancel" => true, "retryOnContentModified" => ["textDocument/semanticTokens/full", "textDocument/semanticTokens/range", "textDocument/semanticTokens/full/delta"]}}, "notebookDocument" => %{"synchronization" => %{"dynamicRegistration" => true, "executionSummarySupport" => true}}, "textDocument" => %{"callHierarchy" => %{"dynamicRegistration" => true}, "codeAction" => %{"codeActionLiteralSupport" => %{"codeActionKind" => %{"valueSet" => ["", "quickfix", "refactor", "refactor.extract", "refactor.inline", "refactor.rewrite", "source", "source.organizeImports"]}}, "dataSupport" => true, "disabledSupport" => true, "dynamicRegistration" => true, "honorsChangeAnnotations" => false, "isPreferredSupport" => true, "resolveSupport" => %{"properties" => ["edit"]}}, "codeLens" => %{"dynamicRegistration" => true}, "colorProvider" => %{"dynamicRegistration" => true}, "completion" => %{"completionItem" => %{"commitCharactersSupport" => true, "deprecatedSupport" => true, "documentationFormat" => ["markdown", "plaintext"], "insertReplaceSupport" => true, "insertTextModeSupport" => %{"valueSet" => [1, 2]}, "labelDetailsSupport" => true, "preselectSupport" => true, "resolveSupport" => %{"properties" => ["documentation", "detail", "additionalTextEdits"]}, "snippetSupport" => true, "tagSupport" => %{"valueSet" => [1]}}, "completionItemKind" => %{"valueSet" => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25]}, "completionList" => %{"itemDefaults" => ["commitCharacters", "editRange", "insertTextFormat", "insertTextMode"]}, "contextSupport" => true, "dynamicRegistration" => true, "insertTextMode" => 2}, "declaration" => %{"dynamicRegistration" => true, "linkSupport" => true}, "definition" => %{"dynamicRegistration" => true, "linkSupport" => true}, "diagnostic" => %{"dynamicRegistration" => true, "relatedDocumentSupport" => false}, "documentHighlight" => %{"dynamicRegistration" => true}, "documentLink" => %{"dynamicRegistration" => true, "tooltipSupport" => true}, "documentSymbol" => %{"dynamicRegistration" => true, "hierarchicalDocumentSymbolSupport" => true, "labelSupport" => true, "symbolKind" => %{"valueSet" => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26]}, "tagSupport" => %{"valueSet" => [1]}}, "foldingRange" => %{"dynamicRegistration" => true, "foldingRange" => %{"collapsedText" => false}, "foldingRangeKind" => %{"valueSet" => ["comment", "imports", "region"]}, "lineFoldingOnly" => true, "rangeLimit" => 5000}, "formatting" => %{"dynamicRegistration" => true}, "hover" => %{"contentFormat" => ["markdown", "plaintext"], "dynamicRegistration" => true}, "implementation" => %{"dynamicRegistration" => true, "linkSupport" => true}, "inlayHint" => %{"dynamicRegistration" => true, "resolveSupport" => %{"properties" => ["tooltip", "textEdits", "label.tooltip", "label.location", "label.command"]}}, "inlineValue" => %{"dynamicRegistration" => true}, "linkedEditingRange" => %{"dynamicRegistration" => true}, "onTypeFormatting" => %{"dynamicRegistration" => true}, "publishDiagnostics" => %{"codeDescriptionSupport" => true, "dataSupport" => true, "relatedInformation" => true, "tagSupport" => %{"valueSet" => [1, 2]}, "versionSupport" => false}, "rangeFormatting" => %{"dynamicRegistration" => true}, "references" => %{"dynamicRegistration" => true}, "rename" => %{"dynamicRegistration" => true, "honorsChangeAnnotations" => true, "prepareSupport" => true, "prepareSupportDefaultBehavior" => 1}, "selectionRange" => %{"dynamicRegistration" => true}, "semanticTokens" => %{"augmentsSyntaxTokens" => true, "dynamicRegistration" => true, "formats" => ["relative"], "multilineTokenSupport" => false, "overlappingTokenSupport" => false, "requests" => %{"full" => %{"delta" => true}, "range" => true}, "serverCancelSupport" => true, "tokenModifiers" => ["declaration", "definition", "readonly", "static", "deprecated", "abstract", "async", "modification", "documentation", "defaultLibrary"], "tokenTypes" => ["namespace", "type", "class", "enum", "interface", "struct", "typeParameter", "parameter", "variable", ...]}, "signatureHelp" => %{"contextSupport" => true, "dynamicRegistration" => true, "signatureInformation" => %{"activeParameterSupport" => true, "documentationFormat" => ["markdown", "plaintext"], "parameterInformation" => %{"labelOffsetSupport" => true}}}, "synchronization" => %{"didSave" => true, "dynamicRegistration" => true, "willSave" => true, "willSaveWaitUntil" => true}, "typeDefinition" => %{"dynamicRegistration" => true, "linkSupport" => true}, "typeHierarchy" => %{"dynamicRegistration" => true}}, "window" => %{"showDocument" => %{"support" => true}, "showMessage" => %{"messageActionItem" => %{"additionalPropertiesSupport" => true}}, "workDoneProgress" => true}, "workspace" => %{"applyEdit" => true, "codeLens" => %{"refreshSupport" => true}, "configuration" => true, "diagnostics" => %{"refreshSupport" => true}, "didChangeConfiguration" => %{"dynamicRegistration" => true}, "didChangeWatchedFiles" => %{"dynamicRegistration" => true, "relativePatternSupport" => true}, "executeCommand" => %{"dynamicRegistration" => true}, "fileOperations" => %{"didCreate" => true, "didDelete" => true, "didRename" => true, "dynamicRegistration" => true, "willCreate" => true, "willDelete" => true, "willRename" => true}, "inlayHint" => %{"refreshSupport" => true}, "inlineValue" => %{"refreshSupport" => true}, "semanticTokens" => %{"refreshSupport" => true}, "symbol" => %{"dynamicRegistration" => true, "resolveSupport" => %{"properties" => ["location.range"]}, "symbolKind" => %{"valueSet" => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, ...]}, "tagSupport" => %{"valueSet" => [1]}}, "workspaceEdit" => %{"changeAnnotationSupport" => %{"groupsOnLabel" => true}, "documentChanges" => true, "failureHandling" => "textOnlyTransactional", "normalizesLineEndings" => true, "resourceOperations" => ["create", "rename", "delete"]}}}, root_uri: "file:///home/cmo/app", project_dir: "/home/cmo/app", settings: %{}, build_diagnostics: [%Mix.Task.Compiler.Diagnostic{file: "/home/cmo/app/lib/app/participation.ex", severity: :warning, message: "invalid association `user` in schema App.Participation: associated schema User does not exist", position: 1, compiler_name: "Elixir", details: nil}], dialyzer_diagnostics: [%Mix.Task.Compiler.Diagnostic{file: "/h (truncated)
[Error - 2:56:49 pm] GenServer #PID<0.326.0> terminating

Expected behavior

Doesn't crash.