fix(jetbrains): render multi-hunk diffs

.changeset/jetbrains-multihunk-diff-viewer.md

@@ -0,0 +1,5 @@
+---
+"@kilocode/kilo-jetbrains": patch
+---
+
+Render multi-hunk modified-file diffs correctly in the JetBrains diff viewer.

packages/kilo-jetbrains/frontend/src/main/kotlin/ai/kilocode/client/diff/DiffPatchReconstruct.kt

@@ -53,11 +53,14 @@ internal object DiffPatchReconstruct {
                 }
             }
         }
-        // Both producers (CLI snapshot and branchDiff) emit a single full-context hunk. A patch with
-        // several hunks, or one whose header lengths don't match the reconstructed body, has elided
-        // context: reconstructing would place every line at the wrong number, so fall back to the
-        // raw-patch view (renderable = false) instead of showing a misaligned side-by-side diff.
-        if (hunks != 1 || oldSeen != oldLen || newSeen != newLen) return DiffSides("", "", false)
+        // A patch may carry several hunks (limited-context git output) or a single full-context hunk.
+        // We concatenate every hunk body into contiguous before/after text: unchanged context lines
+        // anchor each region so the resulting side-by-side still colors adds/removes correctly. The
+        // elided gaps between hunks collapse (line numbers restart at 1), which is acceptable for a
+        // "what changed" view and far better than the all-green raw-patch fallback. We still bail when
+        // there is no hunk, or when the header lengths don't match the reconstructed body (truncated
+        // context), because that would place lines against the wrong side.
+        if (hunks < 1 || oldSeen != oldLen || newSeen != newLen) return DiffSides("", "", false)
         val left = if (added(patch)) "" else before.toString().removeSuffix("\n")
         val right = if (deleted(patch)) "" else after.toString().removeSuffix("\n")
         return DiffSides(left, right, true)

packages/kilo-jetbrains/frontend/src/test/kotlin/ai/kilocode/client/diff/DiffPatchReconstructTest.kt

@@ -133,7 +133,42 @@ class DiffPatchReconstructTest {
     }
 
     @Test
-    fun `multi hunk partial context patch is not renderable`() {
+    fun `multi hunk patch reconstructs concatenated changed regions`() {
+        // Turn/tool diffs are ordinary limited-context git output with several hunks. The reconstruction
+        // stitches each hunk body into contiguous before/after text so the diff editor colors the
+        // changes instead of dumping the raw patch as all-added lines. Inter-hunk gaps collapse.
+        val dto = DiffFileDto(
+            file = "src/A.kt",
+            additions = 2,
+            deletions = 2,
+            patch = """
+                diff --git a/src/A.kt b/src/A.kt
+                --- a/src/A.kt
+                +++ b/src/A.kt
+                @@ -1,3 +1,3 @@
+                 one
+                -two
+                +TWO
+                 three
+                @@ -20,3 +20,3 @@
+                 twenty
+                -x
+                +X
+                 z
+            """.trimIndent(),
+        )
+
+        val sides = DiffPatchReconstruct.sides(dto)
+
+        assertTrue(sides.renderable)
+        assertEquals("one\ntwo\nthree\ntwenty\nx\nz", sides.before)
+        assertEquals("one\nTWO\nthree\ntwenty\nX\nz", sides.after)
+    }
+
+    @Test
+    fun `multi hunk patch with truncated context is not renderable`() {
+        // header claims 3 old / 3 new lines per hunk but the body carries only 2 of each: reconstructing
+        // would misalign the sides, so fall back to the raw-patch view.
         val dto = DiffFileDto(
             file = "src/A.kt",
             additions = 2,

packages/kilo-jetbrains/frontend/src/test/kotlin/ai/kilocode/client/diff/KiloDiffEditorContentTest.kt

@@ -291,6 +291,31 @@ class KiloDiffEditorContentTest : BasePlatformTestCase() {
         assertEquals("hello\nworld", contents[1])
     }
 
+    fun `test diff request reconstructs multi hunk modified patch`() {
+        // Regression: multi-hunk modified diffs used to fall back to an empty original + raw patch on
+        // the right, rendering every line as added. They now reconstruct into a real side-by-side diff.
+        val patch = """
+            diff --git a/src/App.kt b/src/App.kt
+            --- a/src/App.kt
+            +++ b/src/App.kt
+            @@ -1,3 +1,3 @@
+             one
+            -two
+            +TWO
+             three
+            @@ -20,3 +20,3 @@
+             twenty
+            -x
+            +X
+             z
+        """.trimIndent()
+        val request = diffRequest(project, file("src/App.kt", 2, 2, patch = patch)) as SimpleDiffRequest
+        val contents = request.contents.map(::content)
+
+        assertEquals("one\ntwo\nthree\ntwenty\nx\nz", contents[0])
+        assertEquals("one\nTWO\nthree\ntwenty\nX\nz", contents[1])
+    }
+
     fun `test tree displays absolute files relative to workspace`() {
         val parent = Disposer.newDisposable()
         try {