Validate JSON build output against schema.

Author: fniephaus

common.json

@@ -39,7 +39,8 @@
         "python3": "==3.8.10",
         "pip:pylint": "==2.4.4",
         "pip:lazy-object-proxy": "==1.6.0",
-        "pip:ninja_syntax": "==1.7.2"
+        "pip:ninja_syntax": "==1.7.2",
+        "pip:jsonschema": "==4.6.1"
       },
       "python_version": "3"
     },

substratevm/mx.substratevm/mx_substratevm.py

@@ -53,6 +53,9 @@
 from mx_gate import Task
 from mx_unittest import _run_tests, _VMLauncher
 
+import json
+from jsonschema import validate as json_validate
+
 import sys
 
 if sys.version_info[0] < 3:
@@ -356,6 +359,16 @@ def svm_gate_body(args, tasks):
         if t:
             with native_image_context(IMAGE_ASSERTION_FLAGS) as native_image:
                 image_demo_task()
+    
+    with Task('image demos json build output', tasks, tags=[GraalTags.helloworld]) as t:
+        if t:
+            with open(join(suite.dir, '..', 'docs', 'reference-manual', 'native-image', 'assets', 'build-output-schema-v0.9.0.json')) as f:
+                json_schema = json.load(f)
+            with native_image_context(IMAGE_ASSERTION_FLAGS) as native_image:
+                with tempfile.NamedTemporaryFile(prefix="build_json") as json_file:
+                    image_demo_task(['-H:BuildOutputJSONFile', json_file.name])
+                    if not json_validate(json.load(json_file),json_schema):
+                        mx.abort('JSON build output did not validate against the schema.')
 
     with Task('image demos debuginfo', tasks, tags=[GraalTags.helloworld_debug]) as t:
         if t: