fail lint on duplicate rules

a little closer

test duplicate rules

alerter/rules/localStore.go

@@ -43,6 +43,15 @@ func FromPath(path, region string) (*fileStore, error) {
 		}
 		return nil
 	})
+
+	knownRules := map[string]bool{}
+	for _, rule := range s.Rules() {
+		key := rule.Namespace + "/" + rule.Name
+		if knownRules[key] {
+			return nil, fmt.Errorf("duplicate rule %s", key)
+		}
+		knownRules[key] = true
+	}
 	return s, err
 
 }

alerter/rules/localStore_test.go

@@ -72,6 +72,49 @@ spec:
   destination: "peoplewhocare"
 `
 
+var dupeRule = `apiVersion: adx-mon.azure.com/v1
+kind: AlertRule
+metadata:
+  name: alert-rule-one
+  namespace: namespace-one
+spec:
+  database: SomeDB
+  interval: 1h
+  query: |
+    BadThings
+    | where stuff  > 1
+    | summarize count() by region
+    | extend Severity=3
+    | extend  Title = "Bad Things!"
+    | extend  Summary  =  "Bad Things! Oh no"
+    | extend CorrelationId = region
+    | extend TSG="http://gofixit.com"
+  autoMitigateAfter: 2h
+  destination: "peoplewhocare"
+
+---
+
+apiVersion: adx-mon.azure.com/v1
+kind: AlertRule
+metadata:
+  name: alert-rule-one
+  namespace: namespace-one
+spec:
+  database: SomeDB
+  interval: 1h
+  query: |
+    BadThings
+    | where stuff  > 1
+    | summarize count() by region
+    | extend Severity=3
+    | extend  Title = "Bad Things!"
+    | extend  Summary  =  "Bad Things! Oh no"
+    | extend CorrelationId = region
+    | extend TSG="http://gofixit.com"
+  autoMitigateAfter: 2h
+  destination: "peoplewhocare"
+`
+
 // has incorrect indentation, which leads to unknown field errors
 var invalidRuleExample = `apiVersion: adx-mon.azure.com/v1
 kind: AlertRule
@@ -192,6 +235,11 @@ func TestFromPath(t *testing.T) {
 	err = os.WriteFile(multiTestfile, []byte(multiRule), 0644)
 	require.NoError(t, err)
 
+	dupeRuleDirectory := t.TempDir()
+	dupeTestfile := filepath.Join(dupeRuleDirectory, "dupetest.yaml")
+	err = os.WriteFile(dupeTestfile, []byte(dupeRule), 0644)
+	require.NoError(t, err)
+
 	invalidFileDirectory := t.TempDir()
 	invalidTestfile := filepath.Join(invalidFileDirectory, "invalid.yaml")
 	err = os.WriteFile(invalidTestfile, []byte(invalidRuleExample), 0644)
@@ -259,6 +307,11 @@ func TestFromPath(t *testing.T) {
 			path:      invalidAnnotationFileDirectory,
 			expectErr: true,
 		},
+		{
+			name:      "dupe namespace/name in dir should return error",
+			path:      dupeRuleDirectory,
+			expectErr: true,
+		},
 	}
 
 	for _, tc := range testcases {

alerter/service.go

@@ -153,6 +153,7 @@ func Lint(ctx context.Context, opts *AlerterOpts, path string) error {
 	if err != nil {
 		return err
 	}
+
 	logger.Infof("Linting rules from path=%s", path)
 
 	lint := NewLinter()