[BUG] apply_diff fail to strip the line number at last line in SEARCH and REPLACE

[liyi3c]

Problem (one or two sentences)

When using Roo for complex requirement coding, occasionally the last line of the code editor appears with a line number.

Context (who is affected and when)

developers use roo to do coding task may has this issue.
the apply_diff example:

`<<<<<<< SEARCH
1473 | ContactRelaEnum.MS.name(), addressList, contactStatusMap, SensitiveType.ADDRESS, curSector);
1474 | }
1475 | }
1476 | List 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));
=======
1473 | ContactRelaEnum.MS.name(), addressList, contactStatusMap, SensitiveType.ADDRESS, curSector);
1474 | }
1475 | }
1476 |
1477 | //
1478 | if (isAddressDisplayOptimizeEnabled()) {
1479 | homeAddressInfoList = filterAddressesByThreeYearRule(homeAddressInfoList);
1480 | personIdentityInfoList = filterAddressesByThreeYearRule(personIdentityInfoList);
1481 | idNoAddressInfoList = filterAddressesByThreeYearRule(idNoAddressInfoList);
1482 | workAddressInfoList = filterAddressesByThreeYearRule(workAddressInfoList);
1483 | }
1484 |
1485 | List addressInfoList = new ArrayList<>(CollectionUtils.size(repairInfoList) > 10 ? 10
1486 | : CollectionUtils.size(repairInfoList) + CollectionUtils.size(homeAddressInfoList)
1487 | + CollectionUtils.size(idNoAddressInfoList) + CollectionUtils.size(workAddressInfoList)
1488 | + CollectionUtils.size(personIdentityInfoList));

REPLACE`

and after stripLineNumbers, the result is

we debug and found this regex in multi-search-replace.ts will remove the last \n in SEARCH and REPLACE
let matches = [ ...diffContent.matchAll( /(?:^|\n)(?<!\\)<<<<<<< SEARCH>?\s*\n((?:\:start_line:\s*(\d+)\s*\n))?((?:\:end_line:\s*(\d+)\s*\n))?((?<!\\)-------\s*\n)?([\s\S]*?)(?:\n)?(?:(?<=\n)(?<!\\)=======\s*\n)([\s\S]*?)(?:\n)?(?:(?<=\n)(?<!\\)>>>>>>> REPLACE)(?=\n|$)/g, ), ]

1488 | \t\t\t\t\t\t+ CollectionUtils.size(personIdentityInfoList));\r\n
becomes
1488 | \t\t\t\t\t\t+ CollectionUtils.size(personIdentityInfoList));\r

thus stripLineNumbers() cannot match the line number

Reproduction steps

1. Windows, Roo 3.28.2, model is qwen3-coder-480b
2. The input is a feature design document, but that doesn’t matter here
3. After 20–30 LLM rounds, the accumulated multi-turn context exceeds 100K. This may cause the LLM to be unstable when using apply_diff. When Roo begins editing a Java file, there is a certain probability that the last line of the edit will appear with a line number.

Expected result

no line number

Actual result

it has line number at the last edited line

Variations tried (optional)

No response

App Version

3.28.2

API Provider (optional)

OpenAI Compatible

Model Used (optional)

qwen3-coder-480b

Roo Code Task Links (optional)

No response

Relevant logs or errors (optional)

[roomote]

I'm exploring a potential fix for the line number stripping issue in apply_diff. I'll investigate the regex pattern in multi-search-replace.ts and work on preserving the trailing newline character to ensure stripLineNumbers() functions correctly.

[roomote]

I've opened PR #8021 with a fix for this issue: #8021

The fix modifies the stripLineNumbers function to preserve trailing newlines, ensuring that line numbers are correctly stripped from the last line even when the regex captures content without trailing newlines.

The solution includes comprehensive test coverage and all existing tests pass without regression. CI checks are currently running on the PR.