fix issue #1141: immediately report FATAL and PANIC (#1142)

errors reported at the FATAL or PANIC levels should immediately be reported
to Postgres since they ultimately abort the transaction.

ERRORs continue to be converted into panics, and everything else is also
immediately reported to Postgres but since they only emit messages,
there's no change to flow control.

As a drive-by, I also added a few functions to the "bad_ideas" example to interactively test this change.  It's not really feasible for the test suite to somehow test that a test causes the backend, or the entire cluster, to crash, which is what PANIC and FATAL do.

pgrx-examples/bad_ideas/src/lib.rs

@@ -10,10 +10,47 @@ use pgrx::prelude::*;
 use pgrx::{check_for_interrupts, info, register_xact_callback, PgRelation, PgXactCallbackEvent};
 use std::fs::File;
 use std::io::Write;
+use std::panic::catch_unwind;
 use std::process::Command;
 
 pgrx::pg_module_magic!();
 
+#[pg_extern]
+fn panic(s: &str) -> bool {
+    catch_unwind(|| {
+        PANIC!("{}", s);
+    })
+    .ok();
+    true
+}
+
+#[pg_extern]
+fn fatal(s: &str) -> bool {
+    catch_unwind(|| {
+        FATAL!("{}", s);
+    })
+    .ok();
+    true
+}
+
+#[pg_extern]
+fn error(s: &str) -> bool {
+    catch_unwind(|| {
+        error!("{}", s);
+    })
+    .ok();
+    true
+}
+
+#[pg_extern]
+fn warning(s: &str) -> bool {
+    catch_unwind(|| {
+        warning!("{}", s);
+    })
+    .ok();
+    true
+}
+
 #[pg_extern]
 fn exec<'a>(
     command: &'a str,

pgrx-pg-sys/src/submodules/panic.rs

@@ -152,14 +152,18 @@ pub struct ErrorReportWithLevel {
 
 impl ErrorReportWithLevel {
     fn report(self) {
-        // ONLY if the log level is >=ERROR, we convert ourselves into a Rust panic and ask
-        // rust to raise us as a `panic!()`
-        //
-        // Lesser levels (INFO, WARNING, LOG, etc) will just emit a message which isn't a panic condition
-        if crate::ERROR <= self.level as _ {
-            panic_any(self)
-        } else {
-            do_ereport(self)
+        match self.level {
+            // ERRORs get converted into panics so they can perform proper stack unwinding
+            PgLogLevel::ERROR => panic_any(self),
+
+            // FATAL and PANIC are reported directly to Postgres -- they abort the process
+            PgLogLevel::FATAL | PgLogLevel::PANIC => {
+                do_ereport(self);
+                unreachable!()
+            }
+
+            // Everything else (INFO, WARN, LOG, DEBUG, etc) are reported to Postgres too but they only emit messages
+            _ => do_ereport(self),
         }
     }