[mdatagen] Fix metric tests on boolean attributes (open-telemetry#11169)

#### Description

Since commit 8f3ca8a, `mdatagen` improperly generates metric tests:
boolean attributes are always expected to be `true` in the output, no
matter what the injected test value was. For example, [this line in
collector-contrib](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/19b01db307d984e62f81f1880b63327ba092cd81/receiver/apachesparkreceiver/internal/metadata/generated_metrics_test.go#L1250)
is incorrectly changed to expect `true` instead of `false` after
updating mdatagen and running it again.

The reason is [this
line](https://github.com/open-telemetry/opentelemetry-collector/blob/8f3ca8aaf58539e5afab54d365f97624efe7cbc3/cmd/mdatagen/templates/metrics_test.go.tmpl#L182),
which attempts to generate `assert.True` or `assert.False` based on the
expected test value. However, `(attributeInfo $attr).TestValue` does not
return a boolean but the *string* `true` or `false`, both of which are
considered "truthy" by the templating engine.

#### Testing
I manually rebuilt mdatagen, ran `make generate` in collector-contrib,
and ran the tests, to confirm that the test related to the previously
mentioned change was no longer failing.

.chloggen/fix-mdatagen-metrics-bool-attr.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: mdatagen
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix incorrect generation of metric tests with boolean attributes.
+
+# One or more tracking issues or pull requests related to the change
+issues: [11169]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

cmd/mdatagen/internal/samplereceiver/documentation.md

@@ -84,6 +84,7 @@ metrics:
 | ---- | ----------- | ------ |
 | string_attr | Attribute with any string value. | Any Str |
 | boolean_attr | Attribute with a boolean value. | Any Bool |
+| boolean_attr2 | Another attribute with a boolean value. | Any Bool |
 
 ### optional.metric.empty_unit
 

cmd/mdatagen/internal/samplereceiver/metadata.yaml

@@ -43,27 +43,27 @@ resource_attributes:
 
   map.resource.attr:
     description: Resource attribute with a map value.
-    type: map 
+    type: map
     enabled: true
 
   string.resource.attr_disable_warning:
     description: Resource attribute with any string value.
     type: string
-    enabled: true 
+    enabled: true
     warnings:
       if_enabled_not_set: This resource_attribute will be disabled by default soon.
 
   string.resource.attr_remove_warning:
     description: Resource attribute with any string value.
     type: string
-    enabled: false 
+    enabled: false
     warnings:
       if_configured: This resource_attribute is deprecated and will be removed soon.
 
   string.resource.attr_to_be_removed:
     description: Resource attribute with any string value.
     type: string
-    enabled: true 
+    enabled: true
     warnings:
       if_enabled: This resource_attribute is deprecated and will be removed soon.
 
@@ -86,6 +86,12 @@ attributes:
     description: Attribute with a boolean value.
     type: bool
 
+  # This 2nd boolean attribute allows us to test both values for boolean attributes,
+  # as test values are based on the parity of the attribute name length.
+  boolean_attr2:
+    description: Another attribute with a boolean value.
+    type: bool
+
   slice_attr:
     description: Attribute with a slice value.
     type: slice
@@ -114,7 +120,7 @@ metrics:
     unit: "1"
     gauge:
       value_type: double
-    attributes: [string_attr, boolean_attr]
+    attributes: [string_attr, boolean_attr, boolean_attr2]
     warnings:
       if_configured: This metric is deprecated and will be removed soon.
 

cmd/mdatagen/loader_test.go

@@ -149,6 +149,13 @@ func TestLoadMetadata(t *testing.T) {
 						},
 						FullName: "boolean_attr",
 					},
+					"boolean_attr2": {
+						Description: "Another attribute with a boolean value.",
+						Type: ValueType{
+							ValueType: pcommon.ValueTypeBool,
+						},
+						FullName: "boolean_attr2",
+					},
 					"slice_attr": {
 						Description: "Attribute with a slice value.",
 						Type: ValueType{
@@ -190,7 +197,7 @@ func TestLoadMetadata(t *testing.T) {
 						Gauge: &gauge{
 							MetricValueType: MetricValueType{pmetric.NumberDataPointValueTypeDouble},
 						},
-						Attributes: []attributeName{"string_attr", "boolean_attr"},
+						Attributes: []attributeName{"string_attr", "boolean_attr", "boolean_attr2"},
 					},
 					"optional.metric.empty_unit": {
 						Enabled:     false,

cmd/mdatagen/templates/metrics_test.go.tmpl

@@ -179,7 +179,7 @@ func TestMetricsBuilder(t *testing.T) {
 					attrVal, ok {{ if eq $i 0 }}:{{ end }}= dp.Attributes().Get("{{ (attributeInfo $attr).Name }}")
 					assert.True(t, ok)
 					{{- if eq (attributeInfo $attr).Type.String "Bool"}}
-					assert.{{- if (attributeInfo $attr).TestValue }}True{{ else }}False{{- end }}(t, attrVal.{{ (attributeInfo $attr).Type }}()
+					assert.{{- if eq (attributeInfo $attr).TestValue "true" }}True{{ else }}False{{- end }}(t, attrVal.{{ (attributeInfo $attr).Type }}()
 					{{- else }}
 					assert.EqualValues(t, {{ (attributeInfo $attr).TestValue }}, attrVal.{{ (attributeInfo $attr).Type }}()
 					{{- end }}