From fad0db2a0bfce141badfbb88d9056f323f85eb96 Mon Sep 17 00:00:00 2001
From: Sheetal Nandi <shkamat@microsoft.com>
Date: Thu, 10 Sep 2015 09:21:01 -0700
Subject: [PATCH] Report error if output file is among the input files

---
 src/compiler/diagnosticInformationMap.generated.ts | 1 +
 src/compiler/diagnosticMessages.json               | 4 ++++
 src/compiler/emitter.ts                            | 7 +++++++
 3 files changed, 12 insertions(+)

diff --git a/src/compiler/diagnosticInformationMap.generated.ts b/src/compiler/diagnosticInformationMap.generated.ts
index af48e67d964..59f97a9a6ef 100644
--- a/src/compiler/diagnosticInformationMap.generated.ts
+++ b/src/compiler/diagnosticInformationMap.generated.ts
@@ -513,6 +513,7 @@ namespace ts {
         Option_0_cannot_be_specified_without_specifying_option_1: { code: 5052, category: DiagnosticCategory.Error, key: "Option '{0}' cannot be specified without specifying option '{1}'." },
         Option_0_cannot_be_specified_with_option_1: { code: 5053, category: DiagnosticCategory.Error, key: "Option '{0}' cannot be specified with option '{1}'." },
         A_tsconfig_json_file_is_already_defined_at_Colon_0: { code: 5053, category: DiagnosticCategory.Error, key: "A 'tsconfig.json' file is already defined at: '{0}'." },
+        Could_not_write_file_0_which_is_one_of_the_input_files: { code: 5054, category: DiagnosticCategory.Error, key: "Could not write file '{0}' which is one of the input files." },
         Concatenate_and_emit_output_to_single_file: { code: 6001, category: DiagnosticCategory.Message, key: "Concatenate and emit output to single file." },
         Generates_corresponding_d_ts_file: { code: 6002, category: DiagnosticCategory.Message, key: "Generates corresponding '.d.ts' file." },
         Specifies_the_location_where_debugger_should_locate_map_files_instead_of_generated_locations: { code: 6003, category: DiagnosticCategory.Message, key: "Specifies the location where debugger should locate map files instead of generated locations." },
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 7abec7b7c43..b0c877799c9 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -2042,6 +2042,10 @@
         "category": "Error",
         "code": 5053
     },
+    "Could not write file '{0}' which is one of the input files.": {
+        "category": "Error",
+        "code": 5054
+    },
 
     "Concatenate and emit output to single file.": {
         "category": "Message",
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index d84b7b70ada..a37401b9fae 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -7153,6 +7153,13 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
         }
 
         function emitFile(jsFilePath: string, sourceFile?: SourceFile) {
+            if (forEach(host.getSourceFiles(), sourceFile => jsFilePath === sourceFile.fileName)) {
+                // TODO(shkamat) Verify if this works if same file is referred via different paths ..\foo\a.js and a.js refering to same one
+                // Report error and dont emit this file
+                diagnostics.push(createCompilerDiagnostic(Diagnostics.Could_not_write_file_0_which_is_one_of_the_input_files, jsFilePath));
+                return;
+            }
+
             emitJavaScript(jsFilePath, sourceFile);
 
             if (compilerOptions.declaration) {