Make the Fix-It JSON writer produce proper JSON

While here, also sort and deduplicate output entries, and stop having
the Python script try to

The Python script is still messing up the files in some cases, but
I haven't tracked it down. Instead, I have a small Swift program
that does the same thing more easily.

lib/Basic/Edit.cpp

@@ -13,6 +13,7 @@
 #include "llvm/Support/raw_ostream.h"
 #include "swift/Basic/Edit.h"
 #include "swift/Basic/SourceManager.h"
+#include <algorithm>
 
 using namespace swift;
 
@@ -34,8 +35,42 @@ void SourceEdits::addEdit(SourceManager &SM, CharSourceRange Range,
 
 void swift::
 writeEditsInJson(const SourceEdits &AllEdits, llvm::raw_ostream &OS) {
-  OS << "[\n";
-  for (auto &Edit : AllEdits.getEdits()) {
+  // Sort the edits so they occur from the last to the first within a given
+  // source file. That's the order in which applying non-overlapping edits
+  // will succeed.
+  std::vector<SourceEdits::Edit> allEdits(AllEdits.getEdits().begin(),
+                                          AllEdits.getEdits().end());
+  std::sort(allEdits.begin(), allEdits.end(),
+            [&](const SourceEdits::Edit &lhs, const SourceEdits::Edit &rhs) {
+    // Sort first based on the path. This keeps the edits for a given
+    // file together.
+    if (lhs.Path < rhs.Path)
+      return true;
+    else if (lhs.Path > rhs.Path)
+      return false;
+
+    // Then sort based on offset, with larger offsets coming earlier.
+    return lhs.Offset > rhs.Offset;
+  });
+
+  // Remove duplicate edits.
+  allEdits.erase(
+      std::unique(allEdits.begin(), allEdits.end(),
+      [&](const SourceEdits::Edit &lhs, const SourceEdits::Edit &rhs) {
+        return lhs.Path == rhs.Path && lhs.Text == rhs.Text &&
+          lhs.Offset == rhs.Offset && lhs.Length == rhs.Length;
+      }),
+      allEdits.end());
+
+  OS << "[";
+  bool first = true;
+  for (auto &Edit : allEdits) {
+    if (first) {
+      first = false;
+    } else {
+      OS << ",";
+    }
+    OS << "\n";
     OS << " {\n";
     OS << "  \"file\": \"";
     OS.write_escaped(Edit.Path) << "\",\n";
@@ -44,9 +79,9 @@ writeEditsInJson(const SourceEdits &AllEdits, llvm::raw_ostream &OS) {
       OS << "  \"remove\": " << Edit.Length << ",\n";
     if (!Edit.Text.empty()) {
       OS << "  \"text\": \"";
-      OS.write_escaped(Edit.Text) << "\",\n";
+      OS.write_escaped(Edit.Text) << "\"\n";
     }
-    OS << " },\n";
+    OS << " }";
   }
-  OS << "]\n";
+  OS << "\n]\n";
 }

test/diagnostics/verifier.swift

@@ -50,5 +50,5 @@ extension Crap {} // expected-error {{non-nominal type 'Crap' (aka '() -> ()') c
 // CHECK-FIXITS: {
 // CHECK-FIXITS: "file":
 // CHECK-FIXITS: "offset":
-// CHECK-FIXITS: "text": " as! Int",
-// CHECK-FIXITS: },
+// CHECK-FIXITS: "text": " as! Int"
+// CHECK-FIXITS: }

utils/apply-fixit-edits.py

@@ -34,8 +34,6 @@ def apply_edits(path):
     for remap_file in remap_files:
         with open(remap_file) as f:
             json_data = f.read()
-        json_data = json_data.replace(",\n }", "\n }")
-        json_data = json_data.replace(",\n]", "\n]")
         curr_edits = json.loads(json_data)
         for ed in curr_edits:
             fname = ed["file"]