Now also get the example queries as YAML

Via the command line: `python manage.py examples <backend> --format
<format>`.

Via API call: `.../examples/<backend>?format=<format>`.

The only supported formats are `tsv` and `yaml`. The default is `tsv`.

backend/management/commands/examples.py

@@ -1,16 +1,12 @@
-from django.core.management.base import BaseCommand, CommandError
-from django.db.models import TextChoices
+from django.core.management.base import BaseCommand
 from backend.models import Backend
-from backend.models import Link
 from backend.models import Example
-from pprint import pprint
-import requests
-import sys
 import re
 
+
 # Command to get the example queries from the particular backend, with one line
 # per query, in the format:
-# 
+#
 # name of query<TAB>SPARQL query in one line without newlines
 #
 # TODO: Provide option to return result as JSON.
@@ -19,7 +15,7 @@ class Command(BaseCommand):
 
     # Copied from warmup.py, is this really needed?
     def __init__(self, *args, **kwargs):
-        super().__init__( *args, **kwargs)
+        super().__init__(*args, **kwargs)
 
     # Custom log function.
     def log(self, msg=""):
@@ -28,6 +24,12 @@ def log(self, msg=""):
     # Command line arguments.
     def add_arguments(self, parser):
         parser.add_argument("slug", nargs=1, help="Slug of the backend")
+        parser.add_argument(
+            "--output-format",
+            choices=["tsv", "yaml"],
+            default="tsv",
+            help="Output format (default: tsv)",
+        )
 
     # This defines the actual behavior.
     def handle(self, *args, returnLog=False, **options):
@@ -41,33 +43,47 @@ def handle(self, *args, returnLog=False, **options):
         try:
             backend = Backend.objects.filter(slug=slug).get()
         except Exception as e:
-            self.log(f"Error finding config with slug \"{slug}\": {e}")
+            self.log(f'Error finding config with slug "{slug}": {e}')
             return
         # self.log()
         # self.log(f"ID of backend \"{slug}\" is: {backend.pk}")
         # self.log()
         # self.log(f"Keys of Example table: {Example._meta.fields}")
-        result = []
-        for example in Example.objects.filter(backend=backend).order_by("sortKey"):
-            query_name = example.name
-            query_string = self.normalize_query(example.query)
-            result.append(f"{query_name}\t{query_string}")
-        self.log(f"Returning {len(result)} example queries for backend \"{slug}\"")
-        return "\n".join(result) + "\n"
+        output_format = options.get("output_format", "tsv")
+        if output_format == "tsv":
+            result = []
+            for example in Example.objects.filter(backend=backend).order_by("sortKey"):
+                query_name = example.name
+                query_string = self.normalize_query(example.query)
+                result.append(f"{query_name}\t{query_string}")
+            self.log(f'Returning {len(result)} example queries for backend "{slug}"')
+            return "\n".join(result) + "\n"
+        else:
+            result = [f"kb: {backend.slug}", "queries:"]
+            for example in Example.objects.filter(backend=backend).order_by("sortKey"):
+                query_name = example.name
+                # Indent each line by four spaces.
+                query_string = re.sub(r"^", "    ", example.query, flags=re.MULTILINE)
+                result.append(f"- name: {query_name}\n"
+                              f"  query: |\n"
+                              f"{query_string}")
+            return "\n".join(result) + "\n"
+
+
 
     # Helper function for normalizing a query (translated from
     # static/js/helper.js).
     def normalize_query(self, query):
         # Replace # in IRIs by %23.
-        query = re.sub(r'(<[^>]+)#', r'\1%23', query)
+        query = re.sub(r"(<[^>]+)#", r"\1%23", query)
         # Remove comments.
-        query = re.sub(r'#.*\n', ' ', query, flags=re.MULTILINE)
+        query = re.sub(r"#.*\n", " ", query, flags=re.MULTILINE)
         # Re-replace %23 in IRIs by #.
-        query = re.sub(r'(<[^>]+)%23', r'\1#', query)
+        query = re.sub(r"(<[^>]+)%23", r"\1#", query)
         # Replace all sequences of whitespace by a single space.
-        query = re.sub(r'\s+', ' ', query)
+        query = re.sub(r"\s+", " ", query)
         # Remove . before }.
-        query = re.sub(r'\s*\.\s*}', ' }', query)
+        query = re.sub(r"\s*\.\s*}", " }", query)
         # Remove any trailing whitespace.
         query = query.strip()
 

backend/views.py

@@ -182,13 +182,19 @@ def warmup(request, backend, target):
 
 # Handle API request like https://qlever.cs.uni-freiburg.de/api/examples/wikidata
 def examples(request, backend):
-    print_to_log(f'Call of "examples" in views.py with backend = "{backend}"')
+    output_format = request.GET.get("format", "tsv")
+    print_to_log(f"Call of `examples` in `views.py` with backend={backend}"
+                 f" and output_format={output_format}")
     command = ExamplesCommand()
     try:
-        examples_tsv = command.handle(returnLog=True, slug=[backend])
+        examples_tsv = command.handle(returnLog=True, slug=[backend],
+                                      output_format=output_format)
     except Exception as e:
         return HttpResponse("Error: " + str(e), status=500)
-    return HttpResponse(examples_tsv, content_type="text/tab-separated-values")
+    if output_format == "yaml":
+        return HttpResponse(examples_tsv, content_type="text/yaml")
+    else:
+        return HttpResponse(examples_tsv, content_type="text/tab-separated-values")
 
 
 # Handle API request like https://qlever.cs.uni-freiburg.de/api/prefixes/wikidata