Report suppressed warnings count

This also triggers if there is one warning, which seems a little weird,
but it seems mostly reasonable.

src/input/ReaderBackend.cc

@@ -250,13 +250,17 @@ void ReaderBackend::Info(const char* msg) {
     MsgThread::Info(msg);
 }
 
+void ReaderBackend::StopWarningSuppression() {
+    suppress_warnings = false;
+    if ( warnings_suppressed > 0 )
+        Warning(Fmt("Suppressed %zu warning(s)", warnings_suppressed));
+    warnings_suppressed = 0;
+}
+
 void ReaderBackend::FailWarn(bool is_error, const char* msg, bool suppress_future) {
     if ( is_error )
         Error(msg);
     else {
-        // suppress error message when we are already in error mode.
-        // There is no reason to repeat it every second.
-        if ( ! suppress_warnings )
         Warning(msg);
 
         if ( suppress_future )
@@ -264,8 +268,10 @@ void ReaderBackend::FailWarn(bool is_error, const char* msg, bool suppress_futur
     }
 }
 void ReaderBackend::Warning(const char* msg) {
-    if ( suppress_warnings )
+    if ( suppress_warnings ) {
+        warnings_suppressed++;
         return;
+    }
 
     SendOut(new ReaderErrorMessage(frontend, ReaderErrorMessage::WARNING, msg));
     MsgThread::Warning(msg);

src/input/ReaderBackend.h

@@ -203,7 +203,7 @@ public:
      */
     void FailWarn(bool is_error, const char* msg, bool suppress_future = false);
 
-    inline void StopWarningSuppression() { suppress_warnings = false; };
+    void StopWarningSuppression();
 
     // Overridden from MsgThread.
     bool OnHeartbeat(double network_time, double current_time) override;
@@ -365,6 +365,7 @@ private:
     // this is an internal indicator in case the read is currently in a failed state
     // it's used to suppress duplicate error messages.
     bool suppress_warnings = false;
+    size_t warnings_suppressed = 0;
 };
 
 } // namespace zeek::input

src/input/readers/ascii/Ascii.cc

@@ -139,14 +139,14 @@ bool Ascii::OpenFile() {
     if ( ! file.is_open() ) {
         FailWarn(fail_on_file_problem, Fmt("Init: cannot open %s", fname.c_str()), true);
 
-        return ! fail_on_file_problem;
+        return false;
     }
 
     if ( ReadHeader(false) == false ) {
         FailWarn(fail_on_file_problem, Fmt("Init: cannot open %s; problem reading file header", fname.c_str()), true);
 
         file.close();
-        return ! fail_on_file_problem;
+        return false;
     }
 
     if ( ! read_location ) {

testing/btest/Baseline/scripts.base.frameworks.input.invalid-lines-duplicate/.stderrwithoutfirstline

@@ -1,5 +1,7 @@
 ### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
 warning: ..<...>/Input::READER_ASCII: ../input.log, line 3: Not enough fields in line 'hello' of ../input.log. Found 0 fields, want positions 1 and -1
+warning: ..<...>/Input::READER_ASCII: ../input.log, line 9: Suppressed 5 warning(s)
 warning: ..<...>/Input::READER_ASCII: ../input.log, line 10: Not enough fields in line 'hello' of ../input.log. Found 0 fields, want positions 1 and -1
+warning: ..<...>/Input::READER_ASCII: ../input.log, line 16: Suppressed 6 warning(s)
 received termination signal
 >>>