Don't crash on @file when file doesn't exist (fixes #265)

When @file is used and file doesn't exist, just treat it as a normal
argument.

ChangeLog

@@ -1,5 +1,10 @@
 2018-12-23  Jay Berkenbilt  <ejb@ql.org>
 
+	* When specifying @arg on the command line, if the file "arg" does
+	not exist, just treat this is a normal argument. This makes it
+	easier to deal with files whose names start with the @ character.
+	Fixes #265.
+
 	* Tweak completion so it works with zsh as well using
 	bashcompinit.
 

qpdf/qpdf.cc

@@ -1408,7 +1408,24 @@ ArgParser::handleArgFileArguments()
     new_argv.push_back(PointerHolder<char>(true, QUtil::copy_string(argv[0])));
     for (int i = 1; i < argc; ++i)
     {
+        char* argfile = 0;
         if ((strlen(argv[i]) > 1) && (argv[i][0] == '@'))
+        {
+            try
+            {
+                argfile = 1 + argv[i];
+                if (strcmp(argfile, "-") != 0)
+                {
+                    fclose(QUtil::safe_fopen(argfile, "rb"));
+                }
+            }
+            catch (std::runtime_error&)
+            {
+                // The file's not there; treating as regular option
+                argfile = 0;
+            }
+        }
+        if (argfile)
         {
             readArgsFromFile(1+argv[i]);
         }

qpdf/qtest/qpdf.test

@@ -150,7 +150,7 @@ foreach my $c (@completion_tests)
 show_ntests();
 # ----------
 $td->notify("--- Argument Parsing ---");
-$n_tests += 3;
+$n_tests += 4;
 
 $td->runtest("required argument",
              {$td->COMMAND => "qpdf --password minimal.pdf"},
@@ -167,6 +167,11 @@ $td->runtest("required argument with choices",
 	     {$td->REGEXP => "must be given as --decode-level=\\{.*all.*\\}",
                   $td->EXIT_STATUS => 2},
              $td->NORMALIZE_NEWLINES);
+copy("minimal.pdf", '@file.pdf');
+$td->runtest("\@file exists and file doesn't",
+             {$td->COMMAND => "qpdf --check \@file.pdf"},
+             {$td->FILE => "check-at-file.out", $td->EXIT_STATUS => 0},
+             $td->NORMALIZE_NEWLINES);
 
 show_ntests();
 # ----------
@@ -1100,6 +1105,7 @@ $td->notify("--- Overwrite self ---");
 $n_tests += 1;
 
 copy("minimal.pdf", "a.pdf");
+# Also tests @- for reading args from stdin
 $td->runtest("don't overwrite self",
              {$td->COMMAND => "(echo a.pdf; echo a.pdf) | qpdf \@-"},
              {$td->REGEXP => "input file and output file are the same.*",
@@ -3384,5 +3390,5 @@ sub get_md5_checksum
 sub cleanup
 {
     system("rm -rf *.ps *.pnm ?.pdf ?.qdf *.enc* tif1 tif2 tiff-cache");
-    system("rm -rf *split-out* ???-kfo.pdf *.tmpout");
+    system("rm -rf *split-out* ???-kfo.pdf *.tmpout \@file.pdf");
 }

qpdf/qtest/qpdf/check-at-file.out

@@ -0,0 +1,6 @@
+checking @file.pdf
+PDF Version: 1.3
+File is not encrypted
+File is not linearized
+No syntax or stream encoding errors found; the file may still contain
+errors that qpdf cannot detect