do not write unnecessarily

Changes

@@ -1,6 +1,8 @@
 Revision history for {{$dist->name}}
 
 {{$NEXT}}
+  - Don't write file if __DATA__ hasn't changed (gh#2)
+  - Add ->unchanged method (gh#2)
 
 0.01      2024-12-03 17:15:21 -0700
   - initial version

README.md

@@ -77,6 +77,32 @@ $writer->update_file;
 
 Update the existing Perl source file, OR create a new Perl source file with just the `__DATA__` section.
 
+\[version 0.02\]
+
+Starting with version 0.02, this method will not write to the file if the content won't change.
+
+## unchanged
+
+\[version 0.02\]
+
+```perl
+my $bool = $self->unchanged;
+```
+
+Returns:
+
+- \`undef\`
+
+    If </update\_file> hasn't been called yet.
+
+- \`0\`
+
+    If the last call to </update\_file> modified the file.
+
+- \`1\`
+
+    If the last call to </update\_file> did not modify the file.
+
 # CAVEATS
 
 Added text files will get an added trailing new line if they do not already have

lib/Data/Section/Writer.pm

@@ -38,7 +38,7 @@ The name of the Perl source file.  If not provided then the source for the calle
 
   use Path::Tiny ();
   use Carp ();
-  use Class::Tiny qw( perl_filename _files );
+  use Class::Tiny qw( perl_filename _files _same );
   use Ref::Util qw( is_blessed_ref );
   use MIME::Base64 qw(encode_base64);
 
@@ -114,13 +114,18 @@ Returns the C<__DATA__> section.
 
 Update the existing Perl source file, OR create a new Perl source file with just the C<__DATA__> section.
 
+[version 0.02]
+
+Starting with version 0.02, this method will not write to the file if the content won't change.
+
 =cut
 
   sub update_file ($self) {
     my $perl;
+    my $orig;
 
     if(-f $self->perl_filename) {
-      $perl = $self->perl_filename->slurp_utf8;
+      $orig = $perl = $self->perl_filename->slurp_utf8;
 
       if($perl =~ /^__DATA__/) {
         $perl = '';
@@ -137,14 +142,51 @@ Update the existing Perl source file, OR create a new Perl source file with just
       $perl = '';
     }
 
+    $perl .= $self->render_section;
+
+    if(defined $orig && $orig eq $perl) {
+      $self->_same(1);
+      return $self;
+    } else {
+      $self->_same(0);
+    }
+
     # re-write the perl with the
-    $self->perl_filename->spew_utf8(
-      $perl . $self->render_section,
-    );
+    $self->perl_filename->spew_utf8($perl);
 
     return $self;
   }
 
+=head2 unchanged
+
+[version 0.02]
+
+ my $bool = $self->unchanged;
+
+Returns:
+
+=over 4
+
+=item `undef`
+
+If </update_file> hasn't been called yet.
+
+=item `0`
+
+If the last call to </update_file> modified the file.
+
+=item `1`
+
+If the last call to </update_file> did not modify the file.
+
+=back
+
+=cut
+
+  sub unchanged ($self) {
+      return $self->_same;
+  }
+
 }
 
 1;

t/data_section_writer.t

@@ -52,10 +52,20 @@ is(
     };
     call render_section => $section;
 
+    call unchanged => U();
+
     call update_file => object {
       prop isa => 'Data::Section::Writer';
     };
 
+    call unchanged => F();
+
+    call update_file => object {
+      prop isa => 'Data::Section::Writer';
+    };
+
+    call unchanged => T();
+
   },
   'add_section_file',
 );