Replace strings in Dancer2 config with environment variables

lib/Dancer2/Core/Role/ConfigReader.pm

@@ -232,6 +232,12 @@ sub load_config_file {
     }
 
     # TODO handle mergeable entries
+
+    if( defined $config->{'env_var_replace'} && $config->{'env_var_replace'} ) {
+        warn "Apply environment variables to config\n" if $ENV{DANCER_CONFIG_VERBOSE};
+        $self->_replace_env_vars($config);
+    }
+
     return $config;
 }
 
@@ -275,6 +281,48 @@ sub _compile_config_entry {
     return $trigger->( $self, $value, $config );
 }
 
+# Attn. We are traversing along the original data structure all the time,
+# using references, and changing values on the spot, not returning anything.
+sub _replace_env_vars {
+    my ( $self, $entry ) = @_;
+    if( ref $entry ne 'HASH' && ref $entry ne 'ARRAY' ) {
+        croak 'Param entry is not HASH or ARRAY';
+    }
+    if( ref $entry eq 'HASH' ) {
+        foreach my $value (values %{ $entry }) {
+            if( (ref $value) =~ m/(HASH|ARRAY)/msx ) {
+                $self->_replace_env_vars( $value );
+            } elsif( (ref $value) =~ m/(CODE|REF|GLOB)/msx ) {
+                # Pretty much anything else except SCALAR. Do nothing
+                1;
+            } else {
+                if( $value ) {
+                    while( my ($k, $v) = each %ENV) {
+                        $value =~ s/ \$ [{] ENV:$k [}] /$v/gmsx;
+                    }
+                }
+            }
+        }
+    } else {
+        # ref $entry is 'ARRAY'
+        foreach my $value (@{ $entry }) {
+            if( (ref $value) =~ m/(HASH|ARRAY)/msx ) {
+                $self->_replace_env_vars( $value );
+            } elsif( (ref $value) =~ m/(CODE|REF|GLOB)/msx ) {
+                # Pretty much anything else except SCALAR. Do nothing
+                1;
+            } else {
+                if( $value ) {
+                    while( my ($k, $v) = each %ENV) {
+                        $value =~ s/ \$ [{] ENV:$k [}] /$v/gmsx;
+                    }
+                }
+            }
+        }
+    }
+    return;
+}
+
 1;
 
 __END__

t/config_reader.t

@@ -186,4 +186,28 @@ like( exception { Foo->foo() }, qr{Foo::foo}, "traces are enabled", );
     is $f->config_location, $tmpdir;
 }
 
+{
+    # Test _replace_env_vars
+    local $ENV{'SOME_ENV'} = 'Some Value';
+    my $cfg = { aa => 1,
+        coderef => sub { 1; },
+        name => 'Value "${ENV:SOME_ENV}" is.', ## no critic (ValuesAndExpressions::RequireInterpolationOfMetachars)
+        object => (
+            bless { name => 'Value "${ENV:SOME_ENV}" is.' }, ## no critic (ValuesAndExpressions::RequireInterpolationOfMetachars)
+            'An::Object'),
+        a => { bb => 2, b => { cc => 3, c => {
+                    name => 'Value "${ENV:SOME_ENV}" is.', ## no critic (ValuesAndExpressions::RequireInterpolationOfMetachars)
+                    dd => 4, d => [
+                        'ee',
+                        'Value "${ENV:SOME_ENV}" is.', ## no critic (ValuesAndExpressions::RequireInterpolationOfMetachars)
+                    ],
+                }, }, }, };
+    $f->_replace_env_vars( $cfg );
+    is( $cfg->{'name'}, 'Value "Some Value" is.', 'Replace with env var at root' );
+    is( $cfg->{'a'}->{'b'}->{'c'}->{'name'}, 'Value "Some Value" is.', 'Replace with env var at random' );
+    is( $cfg->{'a'}->{'b'}->{'c'}->{'d'}->[1], 'Value "Some Value" is.', 'Replace with env var in an array' );
+    is( $cfg->{'object'}->{'name'}, 'Value "${ENV:SOME_ENV}" is.',  ## no critic (ValuesAndExpressions::RequireInterpolationOfMetachars)
+        'Not Replaced inside an object' );
+}
+
 done_testing;