Bug 1820611 - Document string list behavior with empty lists

docs/dev/core/internal/payload.md

@@ -59,10 +59,18 @@ A [String](../../../book/reference/metrics/string.md) is represented by its stri
 
 A [String List](../../../book/reference/metrics/string_list.md) is represented as an array of strings.
 
+#### Example
+
 ```json
 ["sample string", "another one"]
 ```
 
+An empty list is accepted and send as one:
+
+```json
+[]
+```
+
 ### Timespan
 
 A [Timespan](../../../book/reference/metrics/timespan.md) is represented as an object of their duration as an integer and the time unit.
@@ -288,3 +296,13 @@ A [Rate](../../../book/reference/metrics/rate.md) is represented by its `numerat
     "denominator": 7,
 }
 ```
+
+### Text
+
+A [Text](../../../book/reference/metrics/text.md) is represented by its string value.
+
+#### Example
+
+```json
+"sample string"
+```

docs/user/reference/metrics/string.md

@@ -114,15 +114,15 @@ Glean.searchDefault.name.set("wikipedia");
 
 {{#include ../../../shared/tab_footer.md}}
 
-#### Limits
-
-* Fixed maximum string length: 100. Longer strings are truncated. This is measured in the number of bytes when the string is encoded in UTF-8.
-
 #### Recorded errors
 
 * [`invalid_overflow`](../../user/metrics/error-reporting.md): if the string is too long. (Prior to Glean 31.5.0, this recorded an `invalid_value`).
 * [`invalid_type`](../../user/metrics/error-reporting.md): if a non-string value is given.
 
+#### Limits
+
+* Fixed maximum string length: 100. Longer strings are truncated. This is measured in the number of bytes when the string is encoded in UTF-8.
+
 ## Testing API
 
 ### `testGetValue`

docs/user/reference/metrics/string_list.md

@@ -107,6 +107,7 @@ Glean.search.engines.add("duck duck go");
 ### `set`
 
 Set the metric to a specific list of strings.
+An empty list is accepted.
 
 {{#include ../../../shared/tab_header.md}}
 <div data-lang="Kotlin" class="tab">
@@ -181,8 +182,8 @@ Glean.search.engines.set(["wikipedia", "duck duck go"]);
 
 #### Recorded errors
 
-* `invalid_overflow`: if the string is too long. (Prior to Glean 31.5.0, this recorded an `invalid_value`).
-* `invalid_value`: if the list is too long.
+* [`invalid_overflow`](../../user/metrics/error-reporting.md): if any string in the list is too long, see [Limits](#limits-1) below. (Prior to Glean 31.5.0, this recorded an `invalid_value`).
+* [`invalid_value`](../../user/metrics/error-reporting.md): if the list is too long, see [Limits](#limits-1) below.
 * [`invalid_type`](../../user/metrics/error-reporting.md): if a non-string array is given.
 
 #### Limits

glean-core/rlb/tests/schema.rs

@@ -115,6 +115,10 @@ fn validate_against_schema() {
     stringlist_metric.add("one".into());
     stringlist_metric.add("two".into());
 
+    // Let's make sure an empty array is accepted.
+    let stringlist_metric2 = StringListMetric::new(common("stringlist2"));
+    stringlist_metric2.set(vec![]);
+
     let timespan_metric = TimespanMetric::new(common("timespan"), TimeUnit::Nanosecond);
     timespan_metric.start();
     timespan_metric.stop();