fix(sre): generate error_rate SLO entry instead of empty slos: []

CHANGELOG.md

@@ -7,6 +7,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ---
 
+## [0.4.2] - 2026-03-18
+
+### Fixed
+- **`scaffold sre` empty `slos: []` when `--slo-type error_rate`** — `generate_slo_manifest()` in
+  `cli/scaffold_sre.py` had no branch for the `error_rate` SLO type, leaving `slo.yaml` with an
+  empty `slos: []` list. Sloth/OpenSLO tooling therefore received no SLO objectives. A dedicated
+  `error_rate` SLO entry (with matching SLI queries and alerting config) is now generated when
+  `--slo-type error_rate` is specified.
+
+---
+
 ## [0.4.1] - 2026-03-17
 
 ### Changed

cli/__version__.py

@@ -1,3 +1,3 @@
 """Single source of truth for the devopsos package version."""
 
-__version__ = "0.4.1"
+__version__ = "0.4.2"

cli/scaffold_sre.py

@@ -347,6 +347,28 @@ def generate_slo_manifest(args):
             },
         })
 
+    if args.slo_type in ("error_rate", "all"):
+        slos.append({
+            "name": "error_rate",
+            "description": f"{name} error rate SLO — error rate stays below {round(100 - args.slo_target, 4)}%",
+            "objective": args.slo_target,
+            "sli": {
+                "events": {
+                    "error_query": f"rate(http_requests_total{{job=\"{name}\",status=~\"(5..)\"}}[{{{{.window}}}}])",
+                    "total_query": f"rate(http_requests_total{{job=\"{name}\"}}[{{{{.window}}}}])",
+                }
+            },
+            "alerting": {
+                "name": f"{name.title()}ErrorRateSLO",
+                "labels": {"team": args.team},
+                "annotations": {
+                    "runbook": f"https://wiki.example.com/runbooks/{name}/error-rate",
+                },
+                "page_alert": {"labels": {"severity": "critical"}},
+                "ticket_alert": {"labels": {"severity": "warning"}},
+            },
+        })
+
     if args.slo_type in ("latency", "all"):
         slos.append({
             "name": "latency",

tests/test_comprehensive.py

@@ -854,21 +854,11 @@ def test_slo_manifest_latency_entry(self):
         slo_names = [s["name"] for s in manifest["slos"]]
         assert "latency" in slo_names
 
-    # BUG-2: error_rate SLO type produces empty slos list in manifest
-    @pytest.mark.xfail(
-        strict=True,
-        reason=(
-            "BUG-2: generate_slo_manifest() only checks for 'availability' and "
-            "'latency' slo_type values. When slo_type='error_rate', neither "
-            "condition matches so the slos list is empty. An error_rate SLO "
-            "entry should be generated for slo_type='error_rate'."
-        ),
-    )
     def test_slo_manifest_error_rate_bug(self):
         """
         BUG-2: When slo_type='error_rate', generate_slo_manifest() should
         return at least one SLO entry capturing the error rate objective,
-        but currently returns an empty slos list.
+        and that entry should have name == 'error_rate'.
         """
         args = _sre_args(slo_type="error_rate")
         manifest = scaffold_sre.generate_slo_manifest(args)
@@ -877,13 +867,16 @@ def test_slo_manifest_error_rate_bug(self):
             "Expected at least one SLO entry for error_rate type, "
             "got empty list."
         )
+        slo_names = [s["name"] for s in manifest["slos"]]
+        assert "error_rate" in slo_names
 
     def test_slo_manifest_all_type_has_both_slos(self):
         args = _sre_args(slo_type="all")
         manifest = scaffold_sre.generate_slo_manifest(args)
         slo_names = [s["name"] for s in manifest["slos"]]
         assert "availability" in slo_names
         assert "latency" in slo_names
+        assert "error_rate" in slo_names
 
     def test_alertmanager_config_slack_receiver(self):
         args = _sre_args(slack_channel="#platform-alerts")