4 files changed, 67 insertions, 40 deletions

diff --git a/editors/code/src/cargo.ts b/editors/code/src/cargo.ts
index a328ba9bd..2a2c2e0e1 100644
--- a/editors/code/src/cargo.ts
+++ b/editors/code/src/cargo.ts
@@ -1,6 +1,9 @@
 import * as cp from 'child_process';
+import * as os from 'os';
+import * as path from 'path';
 import * as readline from 'readline';
 import { OutputChannel } from 'vscode';
+import { isValidExecutable } from './util';
 
 interface CompilationArtifact {
     fileName: string;
@@ -10,17 +13,9 @@ interface CompilationArtifact {
 }
 
 export class Cargo {
-    rootFolder: string;
-    env?: Record<string, string>;
-    output: OutputChannel;
-
-    public constructor(cargoTomlFolder: string, output: OutputChannel, env: Record<string, string> | undefined = undefined) {
-        this.rootFolder = cargoTomlFolder;
-        this.output = output;
-        this.env = env;
-    }
+    constructor(readonly rootFolder: string, readonly output: OutputChannel) { }
 
-    public async artifactsFromArgs(cargoArgs: string[]): Promise<CompilationArtifact[]> {
+    private async artifactsFromArgs(cargoArgs: string[]): Promise<CompilationArtifact[]> {
         const artifacts: CompilationArtifact[] = [];
 
         try {
@@ -37,17 +32,13 @@ export class Cargo {
                                 isTest: message.profile.test
                             });
                         }
-                    }
-                    else if (message.reason === 'compiler-message') {
+                    } else if (message.reason === 'compiler-message') {
                         this.output.append(message.message.rendered);
                     }
                 },
-                stderr => {
-                    this.output.append(stderr);
-                }
+                stderr => this.output.append(stderr),
             );
-        }
-        catch (err) {
+        } catch (err) {
             this.output.show(true);
             throw new Error(`Cargo invocation has failed: ${err}`);
         }
@@ -55,9 +46,8 @@ export class Cargo {
         return artifacts;
     }
 
-    public async executableFromArgs(args: string[]): Promise<string> {
-        const cargoArgs = [...args]; // to remain  args unchanged
-        cargoArgs.push("--message-format=json");
+    async executableFromArgs(args: readonly string[]): Promise<string> {
+        const cargoArgs = [...args, "--message-format=json"];
 
         const artifacts = await this.artifactsFromArgs(cargoArgs);
 
@@ -70,24 +60,27 @@ export class Cargo {
         return artifacts[0].fileName;
     }
 
-    runCargo(
+    private runCargo(
         cargoArgs: string[],
         onStdoutJson: (obj: any) => void,
         onStderrString: (data: string) => void
     ): Promise<number> {
-        return new Promise<number>((resolve, reject) => {
-            const cargo = cp.spawn('cargo', cargoArgs, {
+        return new Promise((resolve, reject) => {
+            let cargoPath;
+            try {
+                cargoPath = getCargoPathOrFail();
+            } catch (err) {
+                return reject(err);
+            }
+
+            const cargo = cp.spawn(cargoPath, cargoArgs, {
                 stdio: ['ignore', 'pipe', 'pipe'],
-                cwd: this.rootFolder,
-                env: this.env,
+                cwd: this.rootFolder
             });
 
-            cargo.on('error', err => {
-                reject(new Error(`could not launch cargo: ${err}`));
-            });
-            cargo.stderr.on('data', chunk => {
-                onStderrString(chunk.toString());
-            });
+            cargo.on('error', err => reject(new Error(`could not launch cargo: ${err}`)));
+
+            cargo.stderr.on('data', chunk => onStderrString(chunk.toString()));
 
             const rl = readline.createInterface({ input: cargo.stdout });
             rl.on('line', line => {
@@ -103,4 +96,28 @@ export class Cargo {
             });
         });
     }
-}
\ No newline at end of file
+}
+
+// Mirrors `ra_env::get_path_for_executable` implementation
+function getCargoPathOrFail(): string {
+    const envVar = process.env.CARGO;
+    const executableName = "cargo";
+
+    if (envVar) {
+        if (isValidExecutable(envVar)) return envVar;
+
+        throw new Error(`\`${envVar}\` environment variable points to something that's not a valid executable`);
+    }
+
+    if (isValidExecutable(executableName)) return executableName;
+
+    const standardLocation = path.join(os.homedir(), '.cargo', 'bin', executableName);
+
+    if (isValidExecutable(standardLocation)) return standardLocation;
+
+    throw new Error(
+        `Failed to find \`${executableName}\` executable. ` +
+        `Make sure \`${executableName}\` is in \`$PATH\`, ` +
+        `or set \`${envVar}\` to point to a valid executable.`
+    );
+}
diff --git a/editors/code/src/commands/runnables.ts b/editors/code/src/commands/runnables.ts
index d77e8188c..2ed150e25 100644
--- a/editors/code/src/commands/runnables.ts
+++ b/editors/code/src/commands/runnables.ts
@@ -119,8 +119,11 @@ export function debugSingle(ctx: Ctx): Cmd {
         }
 
         if (!debugEngine) {
-            vscode.window.showErrorMessage(`Install [CodeLLDB](https://marketplace.visualstudio.com/items?itemName=${lldbId})`
-                + ` or [MS C++ tools](https://marketplace.visualstudio.com/items?itemName=${cpptoolsId}) extension for debugging.`);
+            vscode.window.showErrorMessage(
+                `Install [CodeLLDB](https://marketplace.visualstudio.com/items?itemName=${lldbId}) ` +
+                `or [MS C++ tools](https://marketplace.visualstudio.com/items?itemName=${cpptoolsId}) ` +
+                `extension for debugging.`
+            );
             return;
         }
 
diff --git a/editors/code/src/main.ts b/editors/code/src/main.ts
index efd56a84b..9b020d001 100644
--- a/editors/code/src/main.ts
+++ b/editors/code/src/main.ts
@@ -8,10 +8,9 @@ import { activateInlayHints } from './inlay_hints';
 import { activateStatusDisplay } from './status_display';
 import { Ctx } from './ctx';
 import { Config, NIGHTLY_TAG } from './config';
-import { log, assert } from './util';
+import { log, assert, isValidExecutable } from './util';
 import { PersistentState } from './persistent_state';
 import { fetchRelease, download } from './net';
-import { spawnSync } from 'child_process';
 import { activateTaskProvider } from './tasks';
 
 let ctx: Ctx | undefined;
@@ -179,10 +178,7 @@ async function bootstrapServer(config: Config, state: PersistentState): Promise<
 
     log.debug("Using server binary at", path);
 
-    const res = spawnSync(path, ["--version"], { encoding: 'utf8' });
-    log.debug("Checked binary availability via --version", res);
-    log.debug(res, "--version output:", res.output);
-    if (res.status !== 0) {
+    if (!isValidExecutable(path)) {
         throw new Error(`Failed to execute ${path} --version`);
     }
 
diff --git a/editors/code/src/util.ts b/editors/code/src/util.ts
index 6f91f81d6..127a9e911 100644
--- a/editors/code/src/util.ts
+++ b/editors/code/src/util.ts
@@ -1,6 +1,7 @@
 import * as lc from "vscode-languageclient";
 import * as vscode from "vscode";
 import { strict as nativeAssert } from "assert";
+import { spawnSync } from "child_process";
 
 export function assert(condition: boolean, explanation: string): asserts condition {
     try {
@@ -82,3 +83,13 @@ export function isRustDocument(document: vscode.TextDocument): document is RustD
 export function isRustEditor(editor: vscode.TextEditor): editor is RustEditor {
     return isRustDocument(editor.document);
 }
+
+export function isValidExecutable(path: string): boolean {
+    log.debug("Checking availability of a binary at", path);
+
+    const res = spawnSync(path, ["--version"], { encoding: 'utf8' });
+
+    log.debug(res, "--version output:", res.output);
+
+    return res.status === 0;
+}