fix: resolve Windows ENAMETOOLONG error in Claude Code integration (#5631)

src/integrations/claude-code/__tests__/run.spec.ts

@@ -1,4 +1,4 @@
-import { describe, test, expect, vi, beforeEach } from "vitest"
+import { describe, test, expect, vi, beforeEach, afterEach } from "vitest"
 
 // Mock vscode workspace
 vi.mock("vscode", () => ({
@@ -10,6 +10,13 @@ vi.mock("vscode", () => ({
 				},
 			},
 		],
+		fs: {
+			writeFile: vi.fn().mockResolvedValue(undefined),
+			delete: vi.fn().mockResolvedValue(undefined),
+		},
+	},
+	Uri: {
+		file: vi.fn((path: string) => ({ fsPath: path })),
 	},
 }))
 
@@ -86,6 +93,15 @@ vi.mock("readline", () => ({
 	},
 }))
 
+// Mock path and os modules
+vi.mock("path", () => ({
+	join: vi.fn((...args: string[]) => args.join("/")),
+}))
+
+vi.mock("os", () => ({
+	tmpdir: vi.fn(() => "/tmp"),
+}))
+
 describe("runClaudeCode", () => {
 	beforeEach(() => {
 		vi.clearAllMocks()
@@ -287,4 +303,193 @@ describe("runClaudeCode", () => {
 		consoleErrorSpy.mockRestore()
 		await generator.return(undefined)
 	})
+
+	test("should use command line argument for short system prompts", async () => {
+		const { runClaudeCode } = await import("../run")
+		const shortSystemPrompt = "You are a helpful assistant"
+		const options = {
+			systemPrompt: shortSystemPrompt,
+			messages: [{ role: "user" as const, content: "Hello" }],
+		}
+
+		const generator = runClaudeCode(options)
+
+		// Consume at least one item to trigger process spawn
+		await generator.next()
+
+		// Clean up the generator
+		await generator.return(undefined)
+
+		// Verify execa was called with system prompt as command line argument
+		const [, args, execaOptions] = mockExeca.mock.calls[0]
+		expect(args).toContain("--system-prompt")
+		expect(args).toContain(shortSystemPrompt)
+
+		// Verify no environment variable was set for short prompt
+		expect(execaOptions.env?.CLAUDE_CODE_SYSTEM_PROMPT).toBeUndefined()
+	})
+
+	test("should use temporary file for long system prompts to avoid Windows ENAMETOOLONG error", async () => {
+		const { runClaudeCode } = await import("../run")
+		// Create a system prompt longer than MAX_COMMAND_LINE_LENGTH (7000 chars)
+		const longSystemPrompt = "You are a helpful assistant. " + "A".repeat(7000)
+		const options = {
+			systemPrompt: longSystemPrompt,
+			messages: [{ role: "user" as const, content: "Hello" }],
+		}
+
+		const generator = runClaudeCode(options)
+
+		// Consume at least one item to trigger process spawn
+		await generator.next()
+
+		// Clean up the generator
+		await generator.return(undefined)
+
+		// Verify execa was called with --system-prompt @filepath pattern
+		const [, args, execaOptions] = mockExeca.mock.calls[0]
+		expect(args).toContain("--system-prompt")
+
+		// Find the system prompt argument
+		const systemPromptIndex = args.indexOf("--system-prompt")
+		expect(systemPromptIndex).toBeGreaterThan(-1)
+		const systemPromptArg = args[systemPromptIndex + 1]
+
+		// Verify it uses the @filepath pattern for temp files
+		expect(systemPromptArg).toMatch(/^@.*claude-system-prompt-.*\.txt$/)
+
+		// Verify the long system prompt is not directly in the arguments
+		expect(args).not.toContain(longSystemPrompt)
+
+		// Verify no environment variable was set for system prompt
+		expect(execaOptions.env?.CLAUDE_CODE_SYSTEM_PROMPT).toBeUndefined()
+	})
+
+	test("should handle exactly MAX_COMMAND_LINE_LENGTH system prompt using command line", async () => {
+		const { runClaudeCode } = await import("../run")
+		// Create a system prompt exactly at the threshold (7000 chars)
+		const exactLengthPrompt = "A".repeat(7000)
+		const options = {
+			systemPrompt: exactLengthPrompt,
+			messages: [{ role: "user" as const, content: "Hello" }],
+		}
+
+		const generator = runClaudeCode(options)
+
+		// Consume at least one item to trigger process spawn
+		await generator.next()
+
+		// Clean up the generator
+		await generator.return(undefined)
+
+		// Verify execa was called with system prompt as command line argument (at threshold)
+		const [, args, execaOptions] = mockExeca.mock.calls[0]
+		expect(args).toContain("--system-prompt")
+		expect(args).toContain(exactLengthPrompt)
+
+		// Verify no temporary file was used (no @ prefix)
+		const systemPromptIndex = args.indexOf("--system-prompt")
+		const systemPromptArg = args[systemPromptIndex + 1]
+		expect(systemPromptArg).not.toMatch(/^@/)
+	})
+
+	test("should handle system prompt one character over threshold using temporary file", async () => {
+		const { runClaudeCode } = await import("../run")
+		// Create a system prompt one character over the threshold (7001 chars)
+		const overThresholdPrompt = "A".repeat(7001)
+		const options = {
+			systemPrompt: overThresholdPrompt,
+			messages: [{ role: "user" as const, content: "Hello" }],
+		}
+
+		const generator = runClaudeCode(options)
+
+		// Consume at least one item to trigger process spawn
+		await generator.next()
+
+		// Clean up the generator
+		await generator.return(undefined)
+
+		// Verify execa was called with --system-prompt @filepath pattern
+		const [, args, execaOptions] = mockExeca.mock.calls[0]
+		expect(args).toContain("--system-prompt")
+
+		// Find the system prompt argument
+		const systemPromptIndex = args.indexOf("--system-prompt")
+		const systemPromptArg = args[systemPromptIndex + 1]
+
+		// Verify it uses the @filepath pattern for temp files
+		expect(systemPromptArg).toMatch(/^@.*claude-system-prompt-.*\.txt$/)
+
+		// Verify the long system prompt is not directly in the arguments
+		expect(args).not.toContain(overThresholdPrompt)
+
+		// Verify no environment variable was set
+		expect(execaOptions.env?.CLAUDE_CODE_SYSTEM_PROMPT).toBeUndefined()
+	})
+
+	test("should preserve existing environment variables when using temporary files", async () => {
+		const { runClaudeCode } = await import("../run")
+
+		// Mock process.env to have some existing variables
+		const originalEnv = process.env
+		process.env = {
+			...originalEnv,
+			EXISTING_VAR: "existing_value",
+			PATH: "/usr/bin:/bin",
+		}
+
+		const longSystemPrompt = "You are a helpful assistant. " + "A".repeat(7000)
+		const options = {
+			systemPrompt: longSystemPrompt,
+			messages: [{ role: "user" as const, content: "Hello" }],
+		}
+
+		const generator = runClaudeCode(options)
+
+		// Consume at least one item to trigger process spawn
+		await generator.next()
+
+		// Clean up the generator
+		await generator.return(undefined)
+
+		// Verify environment variables include existing ones but no CLAUDE_CODE_SYSTEM_PROMPT
+		const [, , execaOptions] = mockExeca.mock.calls[0]
+		expect(execaOptions.env).toEqual({
+			...process.env,
+			CLAUDE_CODE_MAX_OUTPUT_TOKENS: expect.any(String), // Always set by the implementation
+		})
+
+		// Verify no system prompt environment variable was set
+		expect(execaOptions.env?.CLAUDE_CODE_SYSTEM_PROMPT).toBeUndefined()
+
+		// Restore original environment
+		process.env = originalEnv
+	})
+
+	test("should work with empty system prompt", async () => {
+		const { runClaudeCode } = await import("../run")
+		const options = {
+			systemPrompt: "",
+			messages: [{ role: "user" as const, content: "Hello" }],
+		}
+
+		const generator = runClaudeCode(options)
+
+		// Consume at least one item to trigger process spawn
+		await generator.next()
+
+		// Clean up the generator
+		await generator.return(undefined)
+
+		// Verify execa was called with empty system prompt as command line argument
+		const [, args, execaOptions] = mockExeca.mock.calls[0]
+		expect(args).toContain("--system-prompt")
+		expect(args).toContain("")
+
+		// Verify no temporary file was used (no @ prefix)
+		const systemPromptIndex = args.indexOf("--system-prompt")
+		const systemPromptArg = args[systemPromptIndex + 1]
+		expect(systemPromptArg).not.toMatch(/^@/)
+	})
 })