fix: preserve trailing newlines in stripLineNumbers for apply_diff (#8227)

Co-authored-by: Roo Code <roomote@roocode.com>
Co-authored-by: Matt Rubens <mrubens@users.noreply.github.com>

src/core/diff/strategies/__tests__/multi-search-replace-trailing-newline.spec.ts

@@ -0,0 +1,163 @@
+import { MultiSearchReplaceDiffStrategy } from "../multi-search-replace"
+
+describe("MultiSearchReplaceDiffStrategy - trailing newline preservation", () => {
+	let strategy: MultiSearchReplaceDiffStrategy
+
+	beforeEach(() => {
+		strategy = new MultiSearchReplaceDiffStrategy()
+	})
+
+	it("should preserve trailing newlines in SEARCH content with line numbers", async () => {
+		// This test verifies the fix for issue #8020
+		// The regex should not consume trailing newlines, allowing stripLineNumbers to work correctly
+		const originalContent = `class Example {
+    constructor() {
+        this.value = 0;
+    }
+}`
+		const diffContent = `<<<<<<< SEARCH
+1 | class Example {
+2 |     constructor() {
+3 |         this.value = 0;
+4 |     }
+5 | }
+=======
+class Example {
+    constructor() {
+        this.value = 1;
+    }
+}
+>>>>>>> REPLACE`
+
+		const result = await strategy.applyDiff(originalContent, diffContent)
+		expect(result.success).toBe(true)
+		if (result.success) {
+			expect(result.content).toBe(`class Example {
+    constructor() {
+        this.value = 1;
+    }
+}`)
+		}
+	})
+
+	it("should handle Windows line endings with trailing newlines and line numbers", async () => {
+		const originalContent = "function test() {\r\n    return true;\r\n}\r\n"
+		const diffContent = `<<<<<<< SEARCH
+1 | function test() {
+2 |     return true;
+3 | }
+=======
+function test() {
+    return false;
+}
+>>>>>>> REPLACE`
+
+		const result = await strategy.applyDiff(originalContent, diffContent)
+		expect(result.success).toBe(true)
+		if (result.success) {
+			// Should preserve Windows line endings
+			expect(result.content).toBe("function test() {\r\n    return false;\r\n}\r\n")
+		}
+	})
+
+	it("should handle multiple search/replace blocks with trailing newlines", async () => {
+		const originalContent = `function one() {
+    return 1;
+}
+
+function two() {
+    return 2;
+}`
+		const diffContent = `<<<<<<< SEARCH
+1 | function one() {
+2 |     return 1;
+3 | }
+=======
+function one() {
+    return 10;
+}
+>>>>>>> REPLACE
+
+<<<<<<< SEARCH
+5 | function two() {
+6 |     return 2;
+7 | }
+=======
+function two() {
+    return 20;
+}
+>>>>>>> REPLACE`
+
+		const result = await strategy.applyDiff(originalContent, diffContent)
+		expect(result.success).toBe(true)
+		if (result.success) {
+			expect(result.content).toBe(`function one() {
+    return 10;
+}
+
+function two() {
+    return 20;
+}`)
+		}
+	})
+
+	it("should handle content with line numbers at the last line", async () => {
+		// This specifically tests the scenario from the bug report
+		const originalContent = `                List<ContactInfoItemResp> addressInfoList = new ArrayList<>(CollectionUtils.size(repairInfoList) > 10 ? 10
+                                : CollectionUtils.size(repairInfoList) + CollectionUtils.size(homeAddressInfoList)
+                                                + CollectionUtils.size(idNoAddressInfoList) + CollectionUtils.size(workAddressInfoList)
+                                                + CollectionUtils.size(personIdentityInfoList));`
+
+		const diffContent = `<<<<<<< SEARCH
+1476 |                 List<ContactInfoItemResp> addressInfoList = new ArrayList<>(CollectionUtils.size(repairInfoList) > 10 ? 10
+1477 |                                 : CollectionUtils.size(repairInfoList) + CollectionUtils.size(homeAddressInfoList)
+1478 |                                                 + CollectionUtils.size(idNoAddressInfoList) + CollectionUtils.size(workAddressInfoList)
+1479 |                                                 + CollectionUtils.size(personIdentityInfoList));
+=======
+                
+                // Filter addresses if optimization is enabled
+                if (isAddressDisplayOptimizeEnabled()) {
+                    homeAddressInfoList = filterAddressesByThreeYearRule(homeAddressInfoList);
+                    personIdentityInfoList = filterAddressesByThreeYearRule(personIdentityInfoList);
+                    idNoAddressInfoList = filterAddressesByThreeYearRule(idNoAddressInfoList);
+                    workAddressInfoList = filterAddressesByThreeYearRule(workAddressInfoList);
+                }
+                
+                List<ContactInfoItemResp> addressInfoList = new ArrayList<>(CollectionUtils.size(repairInfoList) > 10 ? 10
+                                : CollectionUtils.size(repairInfoList) + CollectionUtils.size(homeAddressInfoList)
+                                                + CollectionUtils.size(idNoAddressInfoList) + CollectionUtils.size(workAddressInfoList)
+                                                + CollectionUtils.size(personIdentityInfoList));
+>>>>>>> REPLACE`
+
+		const result = await strategy.applyDiff(originalContent, diffContent)
+		expect(result.success).toBe(true)
+		if (result.success) {
+			expect(result.content).toContain("// Filter addresses if optimization is enabled")
+			expect(result.content).toContain("if (isAddressDisplayOptimizeEnabled())")
+			// Verify the last line doesn't have line numbers
+			expect(result.content).not.toContain("1488 |")
+			expect(result.content).not.toContain("1479 |")
+		}
+	})
+
+	it("should correctly strip line numbers even when last line has no trailing newline", async () => {
+		const originalContent = "line 1\nline 2\nline 3" // No trailing newline
+		const diffContent = `<<<<<<< SEARCH
+1 | line 1
+2 | line 2
+3 | line 3
+=======
+line 1
+modified line 2
+line 3
+>>>>>>> REPLACE`
+
+		const result = await strategy.applyDiff(originalContent, diffContent)
+		expect(result.success).toBe(true)
+		if (result.success) {
+			expect(result.content).toBe("line 1\nmodified line 2\nline 3")
+			// Verify no line numbers remain
+			expect(result.content).not.toContain(" | ")
+		}
+	})
+})

src/integrations/misc/extract-text.ts

@@ -163,7 +163,16 @@ export function stripLineNumbers(content: string, aggressive: boolean = false):
 
 	// Join back with original line endings (carriage return (\r) + line feed (\n) or just line feed (\n))
 	const lineEnding = content.includes("\r\n") ? "\r\n" : "\n"
-	return processedLines.join(lineEnding)
+	let result = processedLines.join(lineEnding)
+
+	// Preserve trailing newline if present in original content
+	if (content.endsWith(lineEnding)) {
+		if (!result.endsWith(lineEnding)) {
+			result += lineEnding
+		}
+	}
+
+	return result
 }
 
 /**