osbuild: add description() methods

We already allow loading from a description. This adds the opposite
direction to export Pipelines, Stages, and Assemblers.

test/test_osbuild.py

@@ -0,0 +1,77 @@
+
+import osbuild
+import unittest
+
+
+class TestDescriptions(unittest.TestCase):
+    def test_canonical(self):
+        """Degenerate case. Make sure we always return the same canonical
+        description when passing empty or null values."""
+
+        cases = [
+            {},
+            { "assembler": None },
+            { "stages": [] },
+            { "build": {} },
+            { "build": None }
+        ]
+        for pipeline in cases:
+            with self.subTest(pipeline):
+                self.assertEqual(osbuild.load(pipeline).description(), {})
+
+    def test_stage(self):
+        name = "org.osbuild.test"
+        options = { "one": 1 }
+        cases = [
+            (osbuild.Stage(name, None, None, {}), {"name": name}),
+            (osbuild.Stage(name, None, None, None), {"name": name}),
+            (osbuild.Stage(name, None, None, options), {"name": name, "options": options}),
+        ]
+        for stage, description in cases:
+            with self.subTest(description):
+                self.assertEqual(stage.description(), description)
+
+    def test_assembler(self):
+        name = "org.osbuild.test"
+        options = { "one": 1 }
+        cases = [
+            (osbuild.Assembler(name, {}), {"name": name}),
+            (osbuild.Assembler(name, None), {"name": name}),
+            (osbuild.Assembler(name, options), {"name": name, "options": options}),
+        ]
+        for assembler, description in cases:
+            with self.subTest(description):
+                self.assertEqual(assembler.description(), description)
+
+    def test_pipeline(self):
+        build = osbuild.Pipeline()
+        build.add_stage("org.osbuild.test", { "one": 1 })
+
+        pipeline = osbuild.Pipeline()
+        pipeline.set_build(build)
+        pipeline.add_stage("org.osbuild.test", { "one": 2 })
+        pipeline.set_assembler("org.osbuild.test")
+
+        self.assertEqual(pipeline.description(), {
+              "build": {
+                "stages": [
+                  {
+                    "name": "org.osbuild.test",
+                    "options": { "one": 1 }
+                  }
+                ]
+              },
+              "stages": [
+                {
+                  "name": "org.osbuild.test",
+                  "options": { "one": 2 }
+                }
+              ],
+              "assembler": {
+                "name": "org.osbuild.test"
+              }
+            })
+
+
+if __name__ == "__main__":
+    unittest.main()