fix(process): resolve POSIX backslash basenames through PATH (#2471)

Co-authored-by: morluto <76467478+morluto@users.noreply.github.com>

src/process/capture/ProcessScenarioRuntimeValidation.test.ts

@@ -17,6 +17,28 @@ import {
   resolveProcessScenarioRuntimePaths,
 } from "./ProcessScenarioRuntimeValidation.js";
 import { parseProcessScenario } from "../../domain/process/processScenario.js";
+import { createTestTempDirectory } from "../../../tests/fixtures/temporaryDirectory.js";
+
+it.skipIf(process.platform === "win32")(
+  "resolves a literal backslash in a POSIX executable basename through PATH",
+  async () => {
+    const root = await createTestTempDirectory("rea-process-posix-basename-");
+    const bin = join(root, "bin");
+    await mkdir(bin);
+    const command = "selected\\node";
+    const selected = join(bin, command);
+    await symlink(process.execPath, selected);
+    await expect(resolveExecutable(command, root, bin)).resolves.toBe(selected);
+    const resolved = await resolveProcessScenarioRuntimePaths(
+      parseProcessScenario({
+        executable: command,
+        working_directory: root,
+        environment: { PATH: bin },
+      }),
+    );
+    expect(resolved.executable).toBe(selected);
+  },
+);
 
 it("preserves the caller-selected executable symlink for process invocation", async () => {
   const root = await mkdtemp(join(tmpdir(), "rea-process-executable-alias-"));

src/process/capture/ProcessScenarioRuntimeValidation.ts

@@ -1,6 +1,6 @@
 import { constants as fsConstants } from "node:fs";
 import { access, realpath, stat } from "node:fs/promises";
-import { delimiter, isAbsolute, join, resolve } from "node:path";
+import { delimiter, isAbsolute, join, resolve, sep } from "node:path";
 
 import type { ProcessScenario } from "../../domain/process/processScenario.js";
 import { AnalysisInputError } from "../../domain/analysisErrorCore.js";
@@ -71,7 +71,9 @@ export const resolveExecutable = async (
         : resolve(workingDirectory, directory),
     );
   const candidates =
-    isAbsolute(command) || command.includes("/") || command.includes("\\")
+    isAbsolute(command) ||
+    command.includes("/") ||
+    (sep === "\\" && command.includes("\\"))
       ? [resolve(workingDirectory, command)]
       : directories.map((directory) => join(directory, command));
   const failures: string[] = [];

tests/boundary/process/processCaptureNormalization.test.ts

@@ -28,6 +28,35 @@ const identitySchema = z.object({
 const itWithLinuxCaptureCapability =
   process.platform === "linux" ? itWithCaptureCapability : it.skip;
 
+itWithCaptureCapability(
+  "captures a POSIX PATH executable with a literal backslash in its basename",
+  async () => {
+    const root = await createTestTempDirectory("rea-process-backslash-name-");
+    const bin = join(root, "bin");
+    await mkdir(bin);
+    const command = "selected\\node";
+    const selected = join(bin, command);
+    await symlink(process.execPath, selected);
+    const scenario = parseProcessScenario({
+      executable: command,
+      working_directory: root,
+      environment: { PATH: bin },
+      arguments: ["-e", 'process.stdout.write("selected executable")'],
+      settle_ms: 100,
+    });
+    const result = await captureProcessScenario(scenario);
+    if (!result.ok) throw result.error;
+    expect(result.value.frames.map(({ data }) => data).join("")).toBe(
+      "selected executable",
+    );
+    expect(result.value.exit).toMatchObject({ code: 0, reason: "exited" });
+    expect(result.value.cleanup).toMatchObject({
+      owned_process_group: "verified",
+      temporary_root: "removed",
+    });
+  },
+);
+
 itWithCaptureCapability(
   "preserves numeric reports and original normalized PTY text in Evidence",
   async () => {