feat: syntax highlighting for turtle output

pyproject.toml

@@ -34,6 +34,9 @@ dependencies = [
   "sparqlwrapper~=2.0",
 ]
 
+[project.optional-dependencies]
+highlights = ["pygments ~= 2.17"]
+
 [project.entry-points]
 "xnat.cli" = { img2catalog = "img2catalog.cli_app:cli_click" }
 

src/img2catalog/cli_app.py

@@ -1,11 +1,24 @@
 import logging
+import sys
 from pathlib import Path
 
 import click
 import xnat
 from click_option_group import MutuallyExclusiveOptionGroup, optgroup
 from rdflib import URIRef
 
+if sys.stdout.isatty():
+    try:
+        from pygments import highlight
+        from pygments.formatters import TerminalFormatter
+        from pygments.lexers import TurtleLexer
+
+        syntax_highlight = True
+    except ImportError:
+        syntax_highlight = False
+else:
+    syntax_highlight = False
+
 from img2catalog import log
 from img2catalog.__about__ import __version__
 from img2catalog.configmanager import load_img2catalog_configuration
@@ -205,7 +218,11 @@ def output_dcat(ctx: click.Context, output: click.Path, format: str):
 
     else:
         logger.debug("Sending output to stdout")
-        print(g.serialize(format=format))
+        serialized_output = g.serialize(format=format)
+        if format == "turtle" and syntax_highlight:
+            click.echo(highlight(serialized_output, TurtleLexer(), TerminalFormatter(bg="dark")))
+        else:
+            print(serialized_output)
 
 
 @click.option("-f", "--fdp", envvar=FDP_SERVER_ENV, type=str, required=True, help="URL of FDP to push datasets to")