Function getSnippetForPatch

src/tools/FileEditTool/utils.ts:417–457

(
  patch: StructuredPatchHunk[],
  newFile: string,
)

 * @returns The snippet text with line numbers and the starting line number
 */
export function getSnippetForPatch(
  patch: StructuredPatchHunk[],
  newFile: string,
): { formattedSnippet: string; startLine: number } {
  if (patch.length === 0) {
    // No changes, return empty snippet
    return { formattedSnippet: '', startLine: 1 }
  }

  // Find the first and last changed lines across all hunks
  let minLine = Infinity
  let maxLine = -Infinity

  for (const hunk of patch) {
    if (hunk.oldStart < minLine) {
      minLine = hunk.oldStart
    }
    // For the end line, we need to consider the new lines count since we're showing the new file
    const hunkEnd = hunk.oldStart + (hunk.newLines || 0) - 1
    if (hunkEnd > maxLine) {
      maxLine = hunkEnd
    }
  }

  // Calculate the range with context
  const startLine = Math.max(1, minLine - CONTEXT_LINES)
  const endLine = maxLine + CONTEXT_LINES

  // Split the new file into lines and get the snippet
  const fileLines = newFile.split(/\r?\n/)
  const snippetLines = fileLines.slice(startLine - 1, endLine)
  const snippet = snippetLines.join('\n')

  // Add line numbers
  const formattedSnippet = addLineNumbers({
    content: snippet,
    startLine,
  })

  return { formattedSnippet, startLine }
}

/**
 * Gets a snippet from a file showing the context around a single edit.