feat: Add filtering-strict capability

docs/service_spec.md

@@ -134,6 +134,12 @@ and will send a `?filter=name` query parameter along with streaming/polling requ
 For tests that involve filtering, the test harness will set the `filter` property of the `streaming` or `polling` configuration
 object. The property will either be omitted if no filter is requested, or a non-empty string if requested.
 
+#### Capability `"filtering-strict"`
+
+When initially adding support for the `filtering` capability, the test harness assumed there were no character restrictions on the payload filter key. Later investigation has determined this is not the case.
+
+If this capability is set, the test harness will send a filter key that contains a character that is not allowed in a filter key. The test service should ignore the invalid key and connect as if no filter was specified.
+
 #### Capability `"evaluation-hooks"`
 
 This means that the SDK has support for hooks and has the ability to register evaluation hooks.

sdktests/common_tests_base.go

@@ -2,6 +2,7 @@ package sdktests
 
 import (
 	"fmt"
+	"regexp"
 
 	"github.com/launchdarkly/go-sdk-common/v3/ldcontext"
 	m "github.com/launchdarkly/go-test-helpers/v2/matchers"
@@ -49,6 +50,18 @@ type environmentFilter struct {
 	o.Maybe[string]
 }
 
+// IsValid returns true if the filter key is a valid environment key.
+//
+// In this context, valid means either is missing, or passes the required regex.
+func (p environmentFilter) IsValid() bool {
+	if !p.IsDefined() {
+		return true
+	}
+
+	regex := regexp.MustCompile(`^[a-zA-Z0-9][._\-a-zA-Z0-9]*$`)
+	return regex.MatchString(p.Value())
+}
+
 // String returns a human-readable representation of the filter key,
 // suitable for test output.
 func (p environmentFilter) String() string {
@@ -59,12 +72,15 @@ func (p environmentFilter) String() string {
 // named "filter" with its value.
 // If the filter is not present, it checks that the query parameter map *does not* contain
 // a parameter named "filter".
-func (p environmentFilter) Matcher() m.Matcher {
+func (p environmentFilter) Matcher(strict bool) m.Matcher {
 	hasFilter := m.MapIncluding(
 		m.KV("filter", m.Equal(p.Value())),
 	)
+
 	if !p.IsDefined() {
 		hasFilter = m.Not(hasFilter)
+	} else if strict && !p.IsValid() {
+		hasFilter = m.Not(hasFilter)
 	}
 	return UniqueQueryParameters().Should(hasFilter)
 }

sdktests/common_tests_poll_request.go

@@ -139,7 +139,7 @@ func (c CommonPollingTests) RequestURLPath(t *ldtest.T, pathMatcher func(flagReq
 
 								request := dataSource.Endpoint().RequireConnection(t, time.Second)
 								m.In(t).For("request path").Assert(request.URL.Path, pathMatcher(method))
-								m.In(t).For("filter key").Assert(request.URL.RawQuery, filter.Matcher())
+								m.In(t).For("filter key").Assert(request.URL.RawQuery, filter.Matcher(t.Capabilities().Has(servicedef.CapabilityFilteringStrict)))
 							})
 						}
 					})

sdktests/common_tests_stream_request.go

@@ -87,7 +87,7 @@ func (c CommonStreamingTests) RequestURLPath(t *ldtest.T, pathMatcher func(flagR
 
 								request := dataSource.Endpoint().RequireConnection(t, time.Second)
 								m.In(t).For("request path").Assert(request.URL.Path, pathMatcher(method))
-								m.In(t).For("filter key").Assert(request.URL.RawQuery, filter.Matcher())
+								m.In(t).For("filter key").Assert(request.URL.RawQuery, filter.Matcher(t.Capabilities().Has(servicedef.CapabilityFilteringStrict)))
 							})
 						}
 					})

servicedef/service_params.go

@@ -27,6 +27,7 @@ const (
 	CapabilityTags               = "tags"
 	CapabilityUserType           = "user-type"
 	CapabilityFiltering          = "filtering"
+	CapabilityFilteringStrict    = "filtering-strict"
 	CapabilityAutoEnvAttributes  = "auto-env-attributes"
 	CapabilityMigrations         = "migrations"
 	CapabilityEventSampling      = "event-sampling"