fix rename error if using 'LF' eol in windows (#748)

* fix rename error if using 'LF' eol in windows

* slicing document text by vscode.api

Author: drzunny

src/client/common/utils.ts

@@ -8,7 +8,7 @@ import * as path from 'path';
 import * as fs from 'fs';
 import * as child_process from 'child_process';
 import * as settings from './configSettings';
-import { CancellationToken } from 'vscode';
+import { CancellationToken, TextDocument, Range, Position } from 'vscode';
 import { isNotInstalledError } from './helpers';
 import { mergeEnvVariables, parseEnvFile } from './envFileParser';
 
@@ -301,4 +301,22 @@ export function getCustomEnvVars(): any {
         }
     }
     return null;
+}
+
+export function getWindowsLineEndingCount(document:TextDocument, offset:Number)  {
+    const eolPattern = new RegExp('\r\n', 'g');
+    const readBlock = 1024;
+    let count = 0;
+
+    // In order to prevent the one-time loading of large files from taking up too much memory
+    for (let pos = 0; pos < offset; pos += readBlock)   {
+        let startAt = document.positionAt(pos)
+        let endAt = document.positionAt(pos + readBlock);
+
+        let text = document.getText(new Range(startAt, endAt));
+        let cr = text.match(eolPattern);
+        
+        count += cr ? cr.length : 0;
+    }
+    return count;
 }

src/client/refactor/proxy.ts

@@ -6,7 +6,7 @@ import * as child_process from 'child_process';
 import { IPythonSettings } from '../common/configSettings';
 import { REFACTOR } from '../common/telemetryContracts';
 import { sendTelemetryEvent, Delays } from '../common/telemetry';
-import { IS_WINDOWS, getCustomEnvVars } from '../common/utils';
+import { IS_WINDOWS, getCustomEnvVars, getWindowsLineEndingCount } from '../common/utils';
 import { mergeEnvVariables } from '../common/envFileParser';
 
 export class RefactorProxy extends vscode.Disposable {
@@ -39,8 +39,11 @@ export class RefactorProxy extends vscode.Disposable {
         // get line count
         // Rope always uses LF, instead of CRLF on windows, funny isn't it
         // So for each line, reduce one characer (for CR)
+        // But Not all Windows users use CRLF
         const offset = document.offsetAt(position);
-        return offset - position.line;
+        const winEols = getWindowsLineEndingCount(document, offset);        
+        
+        return offset - winEols;
     }
     rename<T>(document: vscode.TextDocument, name: string, filePath: string, range: vscode.Range, options?: vscode.TextEditorOptions): Promise<T> {
         if (!options) {