feat(core): migrate read_file to 1-based start_line/end_line parameters (#19526)

packages/core/src/utils/fileUtils.ts

@@ -53,7 +53,7 @@ export async function loadWasmBinary(
 }
 
 // Constants for text file processing
-const DEFAULT_MAX_LINES_TEXT_FILE = 2000;
+export const DEFAULT_MAX_LINES_TEXT_FILE = 2000;
 const MAX_LINE_LENGTH_TEXT_FILE = 2000;
 
 // Default values for encoding and separator format
@@ -399,16 +399,17 @@ export interface ProcessedFileReadResult {
  * Reads and processes a single file, handling text, images, and PDFs.
  * @param filePath Absolute path to the file.
  * @param rootDirectory Absolute path to the project root for relative path display.
- * @param offset Optional offset for text files (0-based line number).
- * @param limit Optional limit for text files (number of lines to read).
+ * @param _fileSystemService Currently unused in this function; kept for signature stability.
+ * @param startLine Optional 1-based line number to start reading from.
+ * @param endLine Optional 1-based line number to end reading at (inclusive).
  * @returns ProcessedFileReadResult object.
  */
 export async function processSingleFileContent(
   filePath: string,
   rootDirectory: string,
-  fileSystemService: FileSystemService,
-  offset?: number,
-  limit?: number,
+  _fileSystemService: FileSystemService,
+  startLine?: number,
+  endLine?: number,
 ): Promise<ProcessedFileReadResult> {
   try {
     if (!fs.existsSync(filePath)) {
@@ -474,14 +475,24 @@ export async function processSingleFileContent(
         const lines = content.split('\n');
         const originalLineCount = lines.length;
 
-        const startLine = offset || 0;
-        const effectiveLimit =
-          limit === undefined ? DEFAULT_MAX_LINES_TEXT_FILE : limit;
-        // Ensure endLine does not exceed originalLineCount
-        const endLine = Math.min(startLine + effectiveLimit, originalLineCount);
-        // Ensure selectedLines doesn't try to slice beyond array bounds if startLine is too high
-        const actualStartLine = Math.min(startLine, originalLineCount);
-        const selectedLines = lines.slice(actualStartLine, endLine);
+        let sliceStart = 0;
+        let sliceEnd = originalLineCount;
+
+        if (startLine !== undefined || endLine !== undefined) {
+          sliceStart = startLine ? startLine - 1 : 0;
+          sliceEnd = endLine
+            ? Math.min(endLine, originalLineCount)
+            : Math.min(
+                sliceStart + DEFAULT_MAX_LINES_TEXT_FILE,
+                originalLineCount,
+              );
+        } else {
+          sliceEnd = Math.min(DEFAULT_MAX_LINES_TEXT_FILE, originalLineCount);
+        }
+
+        // Ensure selectedLines doesn't try to slice beyond array bounds
+        const actualStart = Math.min(sliceStart, originalLineCount);
+        const selectedLines = lines.slice(actualStart, sliceEnd);
 
         let linesWereTruncatedInLength = false;
         const formattedLines = selectedLines.map((line) => {
@@ -494,17 +505,18 @@ export async function processSingleFileContent(
           return line;
         });
 
-        const contentRangeTruncated =
-          startLine > 0 || endLine < originalLineCount;
-        const isTruncated = contentRangeTruncated || linesWereTruncatedInLength;
+        const isTruncated =
+          actualStart > 0 ||
+          sliceEnd < originalLineCount ||
+          linesWereTruncatedInLength;
         const llmContent = formattedLines.join('\n');
 
         // By default, return nothing to streamline the common case of a successful read_file.
         let returnDisplay = '';
-        if (contentRangeTruncated) {
+        if (actualStart > 0 || sliceEnd < originalLineCount) {
           returnDisplay = `Read lines ${
-            actualStartLine + 1
-          }-${endLine} of ${originalLineCount} from ${relativePathForDisplay}`;
+            actualStart + 1
+          }-${sliceEnd} of ${originalLineCount} from ${relativePathForDisplay}`;
           if (linesWereTruncatedInLength) {
             returnDisplay += ' (some lines were shortened)';
           }
@@ -517,7 +529,7 @@ export async function processSingleFileContent(
           returnDisplay,
           isTruncated,
           originalLineCount,
-          linesShown: [actualStartLine + 1, endLine],
+          linesShown: [actualStart + 1, sliceEnd],
         };
       }
       case 'image':