From 2c4801ea4731ffe11f44b7bef8abecdd1e6ed4e4 Mon Sep 17 00:00:00 2001
From: Vladimir Matveev <vladima@microsoft.com>
Date: Fri, 15 May 2015 14:28:02 -0700
Subject: [PATCH 1/3] during file update request only changed portion of the
 text from the host

---
 src/services/services.ts | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/services/services.ts b/src/services/services.ts
index 9fb495ee931..3f3e40da367 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1829,7 +1829,34 @@ module ts {
             if (version !== sourceFile.version) {
                 // Once incremental parsing is ready, then just call into this function.
                 if (!disableIncrementalParsing) {
-                    let newSourceFile = updateSourceFile(sourceFile, scriptSnapshot.getText(0, scriptSnapshot.getLength()), textChangeRange, aggressiveChecks);
+                    let newText: string;
+                    
+                    // grab the fragment from the beginning of the original text to the beginning of the span
+                    let prefix = textChangeRange.span.start !== 0
+                        ? sourceFile.text.substr(0, textChangeRange.span.start)
+                        : "";
+                    
+                    // grab the fragment from the end of the span till the end of the original text
+                    let suffix = textChangeRange.span.start + textChangeRange.span.length !== sourceFile.text.length
+                            ? sourceFile.text.substr(textChangeRange.span.start + textChangeRange.span.length)
+                            : "";
+
+                    if (textChangeRange.newLength === 0) {
+                        // edit was a deletion - just combine prefix and suffix
+                        newText = prefix && suffix ? prefix + suffix : prefix || suffix;
+                    }
+                    else {
+                        // it was actual edit, fetch the fragment of new text that correspond to new span
+                        let changedText = scriptSnapshot.getText(textChangeRange.span.start, textChangeRange.span.start + textChangeRange.newLength);
+                        // combine prefix, changed text and suffix
+                        newText = prefix && suffix 
+                            ? prefix + changedText + suffix
+                            : prefix
+                                ? (prefix + changedText) 
+                                : (changedText + suffix);
+                    }
+
+                    let newSourceFile = updateSourceFile(sourceFile, newText, textChangeRange, aggressiveChecks);
                     setSourceFileFields(newSourceFile, scriptSnapshot, version);
                     // after incremental parsing nameTable might not be up-to-date
                     // drop it so it can be lazily recreated later

From d3a2dc0c644c882b7947dba014baa582ed2d6cdd Mon Sep 17 00:00:00 2001
From: Vladimir Matveev <vladima@microsoft.com>
Date: Fri, 15 May 2015 15:28:02 -0700
Subject: [PATCH 2/3] addressed PR feedback

---
 src/services/services.ts | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/services/services.ts b/src/services/services.ts
index 3f3e40da367..a799f421239 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1836,9 +1836,10 @@ module ts {
                         ? sourceFile.text.substr(0, textChangeRange.span.start)
                         : "";
                     
+                    let textChangeRangeEnd = textChangeRange.span.start + textChangeRange.span.length;
                     // grab the fragment from the end of the span till the end of the original text
-                    let suffix = textChangeRange.span.start + textChangeRange.span.length !== sourceFile.text.length
-                            ? sourceFile.text.substr(textChangeRange.span.start + textChangeRange.span.length)
+                    let suffix = textChangeRangeEnd !== sourceFile.text.length
+                            ? sourceFile.text.substr(textChangeRangeEnd)
                             : "";
 
                     if (textChangeRange.newLength === 0) {

From 66a91c33fb8df028c253fde6471509a8e834ad76 Mon Sep 17 00:00:00 2001
From: Vladimir Matveev <vladima@microsoft.com>
Date: Fri, 15 May 2015 16:36:58 -0700
Subject: [PATCH 3/3] use textSpanEnd instead of handrolled version

---
 src/services/services.ts | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/services/services.ts b/src/services/services.ts
index a799f421239..a6a26f0b60b 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1836,11 +1836,10 @@ module ts {
                         ? sourceFile.text.substr(0, textChangeRange.span.start)
                         : "";
                     
-                    let textChangeRangeEnd = textChangeRange.span.start + textChangeRange.span.length;
                     // grab the fragment from the end of the span till the end of the original text
-                    let suffix = textChangeRangeEnd !== sourceFile.text.length
-                            ? sourceFile.text.substr(textChangeRangeEnd)
-                            : "";
+                    let suffix = textSpanEnd(textChangeRange.span) !== sourceFile.text.length
+                        ? sourceFile.text.substr(textSpanEnd(textChangeRange.span))
+                        : "";
 
                     if (textChangeRange.newLength === 0) {
                         // edit was a deletion - just combine prefix and suffix