Error out on lexer failure

src/dfmt/formatter.d

@@ -16,7 +16,17 @@ import dfmt.tokens;
 import dfmt.wrapping;
 import std.array;
 
-void format(OutputRange)(string source_desc, ubyte[] buffer, OutputRange output,
+/**
+ * Formats the code contained in `buffer` into `output`.
+ * Params:
+ *     source_desc = A description of where `buffer` came from. Usually a file name.
+ *     buffer = The raw source code.
+ *     output = The output range that will have the formatted code written to it.
+ *     formatterConfig = Formatter configuration.
+ * Returns: `true` if the formatting succeeded, `false` of a lexing error. This
+ *     function can return `true` if parsing failed.
+ */
+bool format(OutputRange)(string source_desc, ubyte[] buffer, OutputRange output,
         Config* formatterConfig)
 {
     LexerConfig config;
@@ -33,11 +43,18 @@ void format(OutputRange)(string source_desc, ubyte[] buffer, OutputRange output,
     auto visitor = new FormatVisitor(&astInformation);
     visitor.visit(mod);
     astInformation.cleanup();
-    auto tokens = byToken(buffer, config, &cache).array();
+    auto tokenRange = byToken(buffer, config, &cache);
+    auto app = appender!(Token[])();
+    for (; !tokenRange.empty(); tokenRange.popFront())
+        app.put(tokenRange.front());
+    auto tokens = app.data;
+    if (!tokenRange.messages.empty)
+        return false;
     auto depths = generateDepthInfo(tokens);
     auto tokenFormatter = TokenFormatter!OutputRange(buffer, tokens, depths,
             output, &astInformation, formatterConfig);
     tokenFormatter.format();
+    return true;
 }
 
 immutable(short[]) generateDepthInfo(const Token[] tokens) pure nothrow @trusted

src/dfmt/main.d

@@ -19,14 +19,14 @@ static immutable VERSION = () {
 
     version (built_with_dub)
     {
-    	enum DFMT_VERSION = import("dubhash.txt").strip;
+        enum DFMT_VERSION = import("dubhash.txt").strip;
     }
     else
     {
-    	/**
-    	 * Current build's Git commit hash
-    	 */
-    	enum DFMT_VERSION = import("githash.txt").strip;
+        /**
+         * Current build's Git commit hash
+         */
+        enum DFMT_VERSION = import("githash.txt").strip;
     }
 
     return DFMT_VERSION ~ DEBUG_SUFFIX;
@@ -211,7 +211,7 @@ else
                 else
                     break;
             }
-            format("stdin", buffer, output.lockingTextWriter(), &config);
+            return format("stdin", buffer, output.lockingTextWriter(), &config);
         }
         else
         {
@@ -219,6 +219,7 @@ else
 
             if (args.length >= 2)
                 inplace = true;
+            int retVal;
             while (args.length > 0)
             {
                 const path = args.front;
@@ -253,11 +254,13 @@ else
                     f.rawRead(buffer);
                     if (inplace)
                         output = File(path, "wb");
-                    format(path, buffer, output.lockingTextWriter(), &config);
+                    bool formatResult = format(path, buffer, output.lockingTextWriter(), &config);
+                    if (!formatResult)
+                        retVal = 1;
                 }
             }
+            return retVal;
         }
-        return 0;
     }
 }