Add option --warning-exit-0 to exit 0 instead of 3 with warnings

ChangeLog

@@ -1,5 +1,13 @@
 2020-10-20  Jay Berkenbilt  <ejb@ql.org>
 
+	* Add --warning-exit-0 option to the qpdf command line. When
+	specified, qpdf will exit with a status of 0 rather than 3 when
+	there are warnings without errors. Combine with --no-warn to
+	completely ignore warnings.
+
+	* Bug fix: fix further cases in which errors were written to
+	stdout. Fixes #438.
+
 	* Build option: add --disable-rpath option to ./configure, which
 	disables passing -rpath to the linker when building shared
 	libraries with libtool. Fixes #422.

TODO

@@ -1,9 +1,6 @@
 Candidates for upcoming release
 ===============================
 
-* Quick issues:
-  * Add --warning-exit-0 option. Search for --no-warn in the docs.
-
 * Easy build/test
   * #352: building standalone executables (lambda layer)
   * #460: potential malware in fuzzer seed corpus

manual/qpdf-manual.xml

@@ -603,7 +603,9 @@ make
       <listitem>
        <para>
         <literal>0</literal>: no errors or warnings were found. The
-        file may still have problems qpdf can't detect.
+        file may still have problems qpdf can't detect. If
+        <option>--warning-exit-0</option> was specified, exit status 0
+        is used even if there are warnings.
        </para>
       </listitem>
       <listitem>
@@ -618,7 +620,9 @@ make
         able to recover from. In some cases, the resulting file may
         still be damaged. Note that qpdf still exits with status
         <literal>3</literal> if it finds warnings even when
-        <option>--no-warn</option> is specified.
+        <option>--no-warn</option> is specified. With
+        <option>--warning-exit-0</option>, warnings without errors
+        exit with status 0 instead of 3.
        </para>
       </listitem>
      </itemizedlist>
@@ -778,7 +782,19 @@ make
        <para>
         Suppress writing of warnings to stderr. If warnings were
         detected and suppressed, <command>qpdf</command> will still
-        exit with exit code 3.
+        exit with exit code 3. See also
+        <option>--warning-exit-0</option>.
+       </para>
+      </listitem>
+     </varlistentry>
+     <varlistentry>
+      <term><option>--warning-exit-0</option></term>
+      <listitem>
+       <para>
+        If warnings are found but no errors, exit with exit code 0
+        instead 3. When combined with <option>--no-warn</option>, the
+        effect is for <command>qpdf</command> to completely ignore
+        warnings.
        </para>
       </listitem>
      </varlistentry>

qpdf/qpdf.cc

@@ -30,7 +30,7 @@
 #include <qpdf/QIntC.hh>
 
 static int constexpr EXIT_ERROR = 2;
-static int constexpr EXIT_WARNING = 3;
+static int EXIT_WARNING = 3;    // may be changed to 0 at runtime
 
 // For is-encrypted and requires-password
 static int constexpr EXIT_IS_NOT_ENCRYPTED = 2;
@@ -773,6 +773,7 @@ class ArgParser
     void argVerbose();
     void argProgress();
     void argNoWarn();
+    void argWarningExitZero();
     void argDeterministicId();
     void argStaticId();
     void argStaticAesIv();
@@ -1017,6 +1018,7 @@ ArgParser::initOptionTable()
     (*t)["verbose"] = oe_bare(&ArgParser::argVerbose);
     (*t)["progress"] = oe_bare(&ArgParser::argProgress);
     (*t)["no-warn"] = oe_bare(&ArgParser::argNoWarn);
+    (*t)["warning-exit-0"] = oe_bare(&ArgParser::argWarningExitZero);
     (*t)["deterministic-id"] = oe_bare(&ArgParser::argDeterministicId);
     (*t)["static-id"] = oe_bare(&ArgParser::argStaticId);
     (*t)["static-aes-iv"] = oe_bare(&ArgParser::argStaticAesIv);
@@ -1230,6 +1232,7 @@ ArgParser::argHelp()
         << "--verbose               provide additional informational output\n"
         << "--progress              give progress indicators while writing output\n"
         << "--no-warn               suppress warnings\n"
+        << "--warning-exit-0        exit with code 0 instead of 3 if there are warnings\n"
         << "--linearize             generated a linearized (web optimized) file\n"
         << "--replace-input         use in place of specifying an output file; qpdf will\n"
         << "                        replace the input file with the output\n"
@@ -1621,8 +1624,11 @@ ArgParser::argHelp()
         << "Ordinarily, qpdf exits with a status of 0 on success or a status of 2\n"
         << "if any errors occurred.  If there were warnings but not errors, qpdf\n"
         << "exits with a status of 3. If warnings would have been issued but --no-warn\n"
-        << "was given, an exit status of 3 is still used. qpdf does not use exit\n"
+        << "was given, an exit status of 3 is still used. If you want qpdf to exit\n"
-        << "status 1, since that is used by the shell if it can't execute qpdf.\n";
+        << "with status 0 when there are warnings, use the --warning-exit-0 flag.\n"
+        << "When --no-warn and --warning-exit-0 are used together, the effect is for\n"
+        << "qpdf to completely ignore warnings.  qpdf does not use exit status 1,\n"
+        << "since that is used by the shell if it can't execute qpdf.\n";
 }
 
 void
@@ -2118,6 +2124,12 @@ ArgParser::argNoWarn()
     o.suppress_warnings = true;
 }
 
+void
+ArgParser::argWarningExitZero()
+{
+    ::EXIT_WARNING = 0;
+}
+
 void
 ArgParser::argDeterministicId()
 {

qpdf/qtest/qpdf.test

@@ -2472,7 +2472,7 @@ my @badfiles = ("not a PDF file", 			# 1
                 "startxref to space then eof",          # 38
 		);
 
-$n_tests += @badfiles + 6;
+$n_tests += @badfiles + 7;
 
 # Test 6 contains errors in the free table consistency, but we no
 # longer have any consistency check for this since it is not important
@@ -2499,6 +2499,10 @@ for (my $i = 1; $i <= scalar(@badfiles); ++$i)
 $td->runtest("Suppress warnings",
              {$td->COMMAND => "qpdf --no-warn bad14.pdf a.pdf"},
              {$td->STRING => "", $td->EXIT_STATUS => 3});
+$td->runtest("Suppress warnings",
+             {$td->COMMAND =>
+                  "qpdf --no-warn --warning-exit-0 bad14.pdf a.pdf"},
+             {$td->STRING => "", $td->EXIT_STATUS => 0});
 $td->runtest("Suppress warnings with --check",
              {$td->COMMAND => "qpdf --check --no-warn bad14.pdf"},
              {$td->FILE => "bad14-check-no-warn.out",