Allow some tests to compile-check solo.

Allows us to test items that might interfere with other
tests when run in a giant EVAL'd environment.

(E.g. having multiple exports of the same name that are
only conflicting across multiple files)

solo implies that don't have to wrap the code in
anything.

Author: coke

writing-docs/EXAMPLES.md

@@ -89,6 +89,14 @@ example in the code.
         $x = frob();
     =end code
 
+### Complicated Examples
+
+Some examples are too complicated to be run using our EVAL trick.
+Tag these with `:solo`, and they will be run as a separate standalone
+script. This is slower, so only use it on those examples that require
+it. Anything using `unit` or `export` is a good candidate. Note that
+using this tag means the code is not wrapped as it is for the EVAL path.
+
 ### Failures
 
 Some examples fail with compile time exceptions and would interrupt the test

xt/examples-compilation.t

@@ -10,6 +10,7 @@ use v6;
 }
 
 use Test;
+use File::Temp;
 
 use lib 'lib';
 use Pod::Convenience;
@@ -46,6 +47,7 @@ sub walk($arg) {
 
 # Extract all the examples from the given files
 my @examples;
+
 my $counts = BagHash.new;
 for @files -> $file {
     for extract-pod($file.IO).contents -> $chunk {
@@ -65,6 +67,7 @@ for @files -> $file {
                 'ok-test',   $chunk.config<ok-test> // "",
                 'preamble',  $chunk.config<preamble> // "",
                 'method',    $chunk.config<method> // "",
+                'solo',      $chunk.config<solo> // "",
             );
         }
     }
@@ -90,37 +93,52 @@ for @examples -> $eg {
     # Further wrap in an anonymous class (so bare method works)
     # Add in empty routine bodies if needed
 
-    my $code = 'no worries; ';
-    $code ~= "if False \{\nclass :: \{\n";
-    $code ~= $eg<preamble> ~ ";\n";
-
-    for $eg<contents>.lines -> $line {
-        $code ~= $line;
-        if $line.trim.starts-with(any(<multi method proto only sub>)) && !$line.trim.ends-with(any('}',',')) && $eg<method> eq "" {
-           $code ~= " \{}";
-        }
-        if $eg<method> eq "" || $eg<method> eq "False" {
-            $code ~= "\n";
+    my $code;
+    if $eg<solo> {
+        $code = $eg<contents>;
+    } else {
+        $code = 'no worries; ';
+        $code ~= "if False \{\nclass :: \{\n";
+        $code ~= $eg<preamble> ~ ";\n";
+
+        for $eg<contents>.lines -> $line {
+            $code ~= $line;
+            if $line.trim.starts-with(any(<multi method proto only sub>)) && !$line.trim.ends-with(any('}',',')) && $eg<method> eq "" {
+               $code ~= " \{}";
+            }
+            if $eg<method> eq "" || $eg<method> eq "False" {
+                $code ~= "\n";
+            }
         }
+        $code ~= "\{}\n" if $eg<method> eq "True";
+        $code ~= "\n}}";
     }
-    $code ~= "\{}\n" if $eg<method> eq "True";
-    $code ~= "\n}}";
 
     my $msg = "$eg<file> chunk $eg<count> starts with “" ~ starts-with($eg<contents>) ~ "” compiles";
 
-    my $status;
+    my $has-error;
     {
-        temp $*OUT = open :w, $*SPEC.devnull;
-        temp $*ERR = open :w, $*SPEC.devnull;
-        try EVAL $code;
-        $status = $!;
-        close $*OUT;
-        close $*ERR;
+        # Does the test require its own file?
+        if $eg<solo> {
+            my ($tmp_fname, $tmp_io) = tempfile;
+            $tmp_io.spurt: $code, :close;
+            my $proc = Proc::Async.new($*EXECUTABLE, '-c', $tmp_fname);
+            $proc.stdout.tap: {;};
+            $proc.stderr.tap: {;};
+            $has-error = ! await $proc.start;
+        } else {
+            temp $*OUT = open :w, $*SPEC.devnull;
+            temp $*ERR = open :w, $*SPEC.devnull;
+            try EVAL $code;
+            $has-error = $!;
+            close $*OUT;
+            close $*ERR;
+        }
     }
     todo(1) if $eg<todo>;
-    if $status {
+    if $has-error {
         diag $eg<contents>;
-        diag $status;
+        diag $has-error;
         flunk $msg;
     } else {
         pass $msg;