No "invalid" status notification when rust-analyzer fails to discover a workspace

[bstaletic]

YCM relies on receiving rust-analyzer/status with either ready or invalid as a signal that rust-analyzer has finished all the background work at startup.

https://github.com/ycm-core/ycmd/blob/master/ycmd/completers/rust/rust_completer.py#L117-L119

However, the version available through rustup, as well as the current master (844e1aa7), never send the notification if there's no actual workspace. Instead, I only see a window/showMessage notification. An example trace of exchanged messages:

2020-08-20 16:26:28,826 - DEBUG - TX: Sending message: b'Content-Length: 987\r\n\r\n{"id":1,"jsonrpc":"2.0","method":"initialize","params":{"capabilities":{"experimental":{"statusNotification":true},"textDocument":{"codeAction":{"codeActionLiteralSupport":{"codeActionKind":{"valueSet":["","quickfix","refactor","refactor.extract","refactor.inline","refactor.rewrite","source","source.organizeImports"]}}},"completion":{"completionItem":{"documentationFormat":["plaintext","markdown"]},"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]}},"hover":{"contentFormat":["plaintext","markdown"]},"signatureHelp":{"signatureInformation":{"documentationFormat":["plaintext","markdown"],"parameterInformation":{"labelOffsetSupport":true}}},"synchronization":{"didSave":true}},"workspace":{"configuration":true}},"initializationOptions":{},"processId":12967,"rootPath":"/home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd","rootUri":"file:///home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd"}}'
2020-08-20 16:26:28,830 - DEBUG - RX: Received message: b'{"jsonrpc":"2.0","id":1,"result":{"capabilities":{"callHierarchyProvider":true,"codeActionProvider":{"codeActionKinds":["","quickfix","refactor","refactor.extract","refactor.inline","refactor.rewrite"]},"codeLensProvider":{"resolveProvider":true},"completionProvider":{"triggerCharacters":[":","."]},"definitionProvider":true,"documentFormattingProvider":true,"documentHighlightProvider":true,"documentOnTypeFormattingProvider":{"firstTriggerCharacter":"=","moreTriggerCharacter":[".",">"]},"documentSymbolProvider":true,"experimental":{"joinLines":true,"onEnter":true,"parentModule":true,"runnables":{"kinds":["cargo"]},"ssr":true},"foldingRangeProvider":true,"hoverProvider":true,"implementationProvider":true,"referencesProvider":true,"renameProvider":{"prepareProvider":true},"selectionRangeProvider":true,"semanticTokensProvider":{"documentProvider":{"edits":true},"legend":{"tokenModifiers":["documentation","declaration","definition","static","abstract","deprecated","readonly","constant","controlFlow","injected","mutable","consuming","unsafe","attribute"],"tokenTypes":["comment","keyword","string","number","regexp","operator","namespace","type","struct","class","interface","enum","typeParameter","function","member","property","macro","variable","parameter","label","attribute","boolean","builtinType","enumMember","escapeSequence","formatSpecifier","generic","lifetime","punctuation","selfKeyword","typeAlias","union","unresolvedReference"]},"rangeProvider":true},"signatureHelpProvider":{"triggerCharacters":["(",","]},"textDocumentSync":{"change":2,"openClose":true,"save":{}},"typeDefinitionProvider":true,"workspaceSymbolProvider":true},"serverInfo":{"name":"rust-analyzer","version":"844e1aa"}}}'
2020-08-20 16:26:28,831 - DEBUG - TX: Sending notification: b'Content-Length: 52\r\n\r\n{"jsonrpc":"2.0","method":"initialized","params":{}}'
2020-08-20 16:26:28,831 - DEBUG - TX: Sending notification: b'Content-Length: 86\r\n\r\n{"jsonrpc":"2.0","method":"workspace/didChangeConfiguration","params":{"settings":{}}}'
2020-08-20 16:26:28,831 - DEBUG - TX: Sending notification: b'Content-Length: 144\r\n\r\n{"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"languageId":"rust","text":"\\n","uri":"file:///foo.rs","version":1}}}'
2020-08-20 16:26:28,849 - DEBUG - RX: Received message: b'{"jsonrpc":"2.0","method":"window/showMessage","params":{"message":"rust-analyzer failed to discover workspace","type":1}}'
2020-08-20 16:26:28,849 - DEBUG - RX: Received message: b'{"jsonrpc":"2.0","id":0,"method":"client/registerCapability","params":{"registrations":[{"id":"textDocument/didSave","method":"textDocument/didSave","registerOptions":{"documentSelector":[{"pattern":"**/*.rs"},{"pattern":"**/Cargo.toml"},{"pattern":"**/Cargo.lock"}],"includeText":false}}]}}'
2020-08-20 16:26:28,849 - DEBUG - TX: Sending response: b'Content-Length: 38\r\n\r\n{"id":0,"jsonrpc":"2.0","result":null}'
2020-08-20 16:26:28,855 - DEBUG - RX: Received message: b'{"jsonrpc":"2.0","id":1,"method":"workspace/configuration","params":{"items":[{"section":"rust-analyzer"}]}}'
2020-08-20 16:26:28,855 - DEBUG - TX: Sending response: b'Content-Length: 40\r\n\r\n{"id":1,"jsonrpc":"2.0","result":[null]}'

This is the rust-analyzer log with RA_LOG set to rust-analyzer=trace:

[INFO  rust_analyzer] lifecycle: server started
[INFO  rust_analyzer::config] Config::update({})
[INFO  rust_analyzer::main_loop] initial config: Config {
        client_caps: ClientCapsConfig {
            location_link: false,
            line_folding_only: false,
            hierarchical_symbols: false,
            code_action_literals: true,
            work_done_progress: false,
            code_action_group: false,
            resolve_code_action: false,
            hover_actions: false,
            status_notification: true,
            signature_help_label_offsets: true,
        },
        publish_diagnostics: true,
        diagnostics: DiagnosticsConfig {
            disable_experimental: false,
            disabled: {},
        },
        diagnostics_map: DiagnosticsMapConfig {
            warnings_as_info: [],
            warnings_as_hint: [],
        },
        lru_capacity: None,
        proc_macro_srv: None,
        files: FilesConfig {
            watcher: Notify,
            exclude: [],
        },
        notifications: NotificationsConfig {
            cargo_toml_not_found: true,
        },
        cargo_autoreload: true,
        cargo: CargoConfig {
            no_default_features: false,
            all_features: false,
            features: [],
            load_out_dirs_from_check: false,
            target: None,
        },
        rustfmt: Rustfmt {
            extra_args: [],
        },
        flycheck: Some(
            CargoCommand {
                command: "check",
                target_triple: None,
                all_targets: true,
                no_default_features: false,
                all_features: false,
                features: [],
                extra_args: [],
            },
        ),
        inlay_hints: InlayHintsConfig {
            type_hints: true,
            parameter_hints: true,
            chaining_hints: true,
            max_length: None,
        },
        completion: CompletionConfig {
            enable_postfix_completions: true,
            add_call_parenthesis: true,
            add_call_argument_snippets: true,
            snippet_cap: None,
        },
        assist: AssistConfig {
            snippet_cap: None,
            allowed: None,
        },
        call_info_full: true,
        lens: LensConfig {
            run: true,
            debug: true,
            implementations: true,
        },
        hover: HoverConfig {
            implementations: true,
            run: true,
            debug: true,
            goto_type_def: true,
        },
        with_sysroot: true,
        linked_projects: [],
        root_path: AbsPathBuf(
            "/home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd",
        ),
    }
[INFO  rust_analyzer::main_loop] handle_event(Notification(Notification { method: "workspace/didChangeConfiguration", params: Object({"settings": Object({})}) }))
[INFO  rust_analyzer::main_loop] handle_event(Workspaces([]))
[INFO  rust_analyzer::reload] reloading projects: []
[INFO  rust_analyzer::main_loop] handle_event(Notification { method: "textDocument/didOpen" })
[INFO  rust_analyzer::main_loop] handle_event(Response(Response { id: RequestId(U64(0)), result: None, error: None }))
[INFO  rust_analyzer::main_loop] handle_event(Response(Response { id: RequestId(U64(1)), result: Some(Array([Null])), error: None }))
[DEBUG rust_analyzer::main_loop] config update response: 'Response { id: RequestId(U64(1)), result: Some(Array([Null])), error: None }
[INFO  rust_analyzer::config] Config::update(null)