Function reconstructNewFile

core/edit/lazy/deterministic.ts:23–99

(
  oldFile: string,
  newFile: string,
  lazyBlockReplacements: AstReplacements,
)

}

function reconstructNewFile(
  oldFile: string,
  newFile: string,
  lazyBlockReplacements: AstReplacements,
): string {
  // Sort acc by reverse line number
  lazyBlockReplacements
    .sort((a, b) => a.nodeToReplace.startIndex - b.nodeToReplace.startIndex)
    .reverse();

  // Reconstruct entire file by replacing lazy blocks with the replacement nodes
  const oldFileLines = oldFile.split("\n");
  const newFileChars = newFile.split("");
  for (const {
    nodeToReplace: lazyBlockNode,
    replacementNodes,
  } of lazyBlockReplacements) {
    // Get the full string from the replacement nodes
    let replacementText = "";
    if (replacementNodes.length > 0) {
      const startPosition = replacementNodes[0].startPosition;
      const endPosition =
        replacementNodes[replacementNodes.length - 1].endPosition;
      const replacementLines = oldFileLines.slice(
        startPosition.row,
        endPosition.row + 1,
      );
      replacementLines[0] = replacementLines[0].slice(startPosition.column);
      replacementLines[replacementLines.length - 1] = replacementLines[
        replacementLines.length - 1
      ].slice(0, endPosition.column);
      replacementText = replacementLines.join("\n");

      // Replace the lazy block
      newFileChars.splice(
        lazyBlockNode.startIndex,
        lazyBlockNode.text.length,
        replacementText,
      );
    } else {
      // If there are no replacements, then we want to strip the surrounding whitespace
      // The example in calculator-exp.js.diff is a test where this is necessary
      const lazyBlockStart = lazyBlockNode.startIndex;
      const lazyBlockEnd = lazyBlockNode.endIndex - 1;

      // Remove leading whitespace up to two new lines
      let startIndex = lazyBlockStart;
      let newLinesFound = 0;
      while (
        startIndex > 0 &&
        newFileChars[startIndex - 1]?.trim() === "" &&
        newLinesFound < 2
      ) {
        startIndex--;
        if (newFileChars[startIndex - 1] === "\n") {
          newLinesFound++;
        }
      }