feat: Colorize cargo check diagnostics in VSCode via text decorations

crates/flycheck/src/lib.rs

@@ -47,6 +47,7 @@ pub enum FlycheckConfig {
         features: Vec<String>,
         extra_args: Vec<String>,
         extra_env: FxHashMap<String, String>,
+        ansi_color_output: bool,
     },
     CustomCommand {
         command: String,
@@ -293,12 +294,21 @@ impl FlycheckActor {
                 extra_args,
                 features,
                 extra_env,
+                ansi_color_output,
             } => {
                 let mut cmd = Command::new(toolchain::cargo());
                 cmd.arg(command);
                 cmd.current_dir(&self.root);
-                cmd.args(["--workspace", "--message-format=json", "--manifest-path"])
-                    .arg(self.root.join("Cargo.toml").as_os_str());
+                cmd.arg("--workspace");
+
+                cmd.arg(if *ansi_color_output {
+                    "--message-format=json-diagnostic-rendered-ansi"
+                } else {
+                    "--message-format=json"
+                });
+
+                cmd.arg("--manifest-path");
+                cmd.arg(self.root.join("Cargo.toml").as_os_str());
 
                 for target in target_triples {
                     cmd.args(["--target", target.as_str()]);

crates/rust-analyzer/src/config.rs

@@ -160,7 +160,9 @@ config_data! {
         check_noDefaultFeatures | checkOnSave_noDefaultFeatures: Option<bool>         = "null",
         /// Override the command rust-analyzer uses instead of `cargo check` for
         /// diagnostics on save. The command is required to output json and
-        /// should therefore include `--message-format=json` or a similar option.
+        /// should therefore include `--message-format=json` or a similar option
+        /// (if your client supports the `colorDiagnosticOutput` experimental
+        /// capability, you can use `--message-format=json-diagnostic-rendered-ansi`).
         ///
         /// If you're changing this because you're using some tool wrapping
         /// Cargo, you might also want to change
@@ -1006,6 +1008,11 @@ impl Config {
         self.experimental("serverStatusNotification")
     }
 
+    /// Whether the client supports colored output for full diagnostics from `checkOnSave`.
+    pub fn color_diagnostic_output(&self) -> bool {
+        self.experimental("colorDiagnosticOutput")
+    }
+
     pub fn publish_diagnostics(&self) -> bool {
         self.data.diagnostics_enable
     }
@@ -1204,6 +1211,7 @@ impl Config {
                 },
                 extra_args: self.data.check_extraArgs.clone(),
                 extra_env: self.check_on_save_extra_env(),
+                ansi_color_output: self.color_diagnostic_output(),
             },
         }
     }

docs/dev/lsp-extensions.md

@@ -792,3 +792,29 @@ export interface ClientCommandOptions {
     commands: string[];
 }
 ```
+
+## Colored Diagnostic Output
+
+**Experimental Client Capability:** `{ "colorDiagnosticOutput": boolean }`
+
+If this capability is set, the "full compiler diagnostics" provided by `checkOnSave`
+will include ANSI color and style codes to render the diagnostic in a similar manner
+as `cargo`. This is translated into `--message-format=json-diagnostic-rendered-ansi`
+when flycheck is run, instead of the default `--message-format=json`.
+
+The full compiler rendered diagnostics are included in the server response
+regardless of this capability:
+
+```typescript
+// https://microsoft.github.io/language-server-protocol/specifications/specification-current#diagnostic
+export interface Diagnostic {
+    ...
+    data?: {
+        /**
+         * The human-readable compiler output as it would be printed to a terminal.
+         * Includes ANSI color and style codes if the client has set the experimental
+         * `colorDiagnosticOutput` capability.
+         */
+        rendered?: string;
+    };
+}

docs/user/generated_config.adoc

@@ -173,7 +173,9 @@ Whether to pass `--no-default-features` to Cargo. Defaults to
 --
 Override the command rust-analyzer uses instead of `cargo check` for
 diagnostics on save. The command is required to output json and
-should therefore include `--message-format=json` or a similar option.
+should therefore include `--message-format=json` or a similar option
+(if your client supports the `colorDiagnosticOutput` experimental
+capability, you can use `--message-format=json-diagnostic-rendered-ansi`).
 
 If you're changing this because you're using some tool wrapping
 Cargo, you might also want to change

editors/code/package.json

@@ -35,6 +35,7 @@
         "test": "cross-env TEST_VARIABLE=test node ./out/tests/runTests.js"
     },
     "dependencies": {
+        "anser": "^2.1.1",
         "d3": "^7.6.1",
         "d3-graphviz": "^5.0.2",
         "vscode-languageclient": "^8.0.2"
@@ -643,7 +644,7 @@
                     ]
                 },
                 "rust-analyzer.check.overrideCommand": {
-                    "markdownDescription": "Override the command rust-analyzer uses instead of `cargo check` for\ndiagnostics on save. The command is required to output json and\nshould therefore include `--message-format=json` or a similar option.\n\nIf you're changing this because you're using some tool wrapping\nCargo, you might also want to change\n`#rust-analyzer.cargo.buildScripts.overrideCommand#`.\n\nIf there are multiple linked projects, this command is invoked for\neach of them, with the working directory being the project root\n(i.e., the folder containing the `Cargo.toml`).\n\nAn example command would be:\n\n```bash\ncargo check --workspace --message-format=json --all-targets\n```\n.",
+                    "markdownDescription": "Override the command rust-analyzer uses instead of `cargo check` for\ndiagnostics on save. The command is required to output json and\nshould therefore include `--message-format=json` or a similar option\n(if your client supports the `colorDiagnosticOutput` experimental\ncapability, you can use `--message-format=json-diagnostic-rendered-ansi`).\n\nIf you're changing this because you're using some tool wrapping\nCargo, you might also want to change\n`#rust-analyzer.cargo.buildScripts.overrideCommand#`.\n\nIf there are multiple linked projects, this command is invoked for\neach of them, with the working directory being the project root\n(i.e., the folder containing the `Cargo.toml`).\n\nAn example command would be:\n\n```bash\ncargo check --workspace --message-format=json --all-targets\n```\n.",
                     "default": null,
                     "type": [
                         "null",

editors/code/src/client.ts

@@ -1,8 +1,10 @@
+import * as anser from "anser";
 import * as lc from "vscode-languageclient/node";
 import * as vscode from "vscode";
 import * as ra from "../src/lsp_ext";
 import * as Is from "vscode-languageclient/lib/common/utils/is";
 import { assert } from "./util";
+import * as diagnostics from "./diagnostics";
 import { WorkspaceEdit } from "vscode";
 import { Config, substituteVSCodeVariables } from "./config";
 import { randomUUID } from "crypto";
@@ -120,12 +122,12 @@ export async function createClient(
             },
             async handleDiagnostics(
                 uri: vscode.Uri,
-                diagnostics: vscode.Diagnostic[],
+                diagnosticList: vscode.Diagnostic[],
                 next: lc.HandleDiagnosticsSignature
             ) {
                 const preview = config.previewRustcOutput;
                 const errorCode = config.useRustcErrorCode;
-                diagnostics.forEach((diag, idx) => {
+                diagnosticList.forEach((diag, idx) => {
                     // Abuse the fact that VSCode leaks the LSP diagnostics data field through the
                     // Diagnostic class, if they ever break this we are out of luck and have to go
                     // back to the worst diagnostics experience ever:)
@@ -138,9 +140,10 @@ export async function createClient(
                         ?.rendered;
                     if (rendered) {
                         if (preview) {
+                            const decolorized = anser.ansiToText(rendered);
                             const index =
-                                rendered.match(/^(note|help):/m)?.index || rendered.length;
-                            diag.message = rendered
+                                decolorized.match(/^(note|help):/m)?.index || rendered.length;
+                            diag.message = decolorized
                                 .substring(0, index)
                                 .replace(/^ -->[^\n]+\n/m, "");
                         }
@@ -154,16 +157,16 @@ export async function createClient(
                         }
                         diag.code = {
                             target: vscode.Uri.from({
-                                scheme: "rust-analyzer-diagnostics-view",
-                                path: "/diagnostic message",
+                                scheme: diagnostics.URI_SCHEME,
+                                path: `/diagnostic message [${idx.toString()}]`,
                                 fragment: uri.toString(),
                                 query: idx.toString(),
                             }),
                             value: value ?? "Click for full compiler diagnostic",
                         };
                     }
                 });
-                return next(uri, diagnostics);
+                return next(uri, diagnosticList);
             },
             async provideHover(
                 document: vscode.TextDocument,
@@ -330,6 +333,7 @@ class ExperimentalFeatures implements lc.StaticFeature {
         caps.codeActionGroup = true;
         caps.hoverActions = true;
         caps.serverStatusNotification = true;
+        caps.colorDiagnosticOutput = true;
         caps.commands = {
             commands: [
                 "rust-analyzer.runSingle",