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feat(evaluation)!: add $flagd.timestamp and fix property naming per specification (#36)
## Description The evaluator was missing `$flagd.timestamp` support and using non-compliant property naming (`flagKey` instead of `$flagd.flagKey`). Both properties must match the pattern `^\\$flagd\\.((timestamp)|(flagKey))$` per `schemas/targeting.json` lines 48-54. **Changes:** - Added `$flagd.timestamp` injection (unix seconds via `SystemTime`, defaults to 0 if unavailable) - Fixed `flagKey` → `$flagd.flagKey` to match specification - Store as nested object `{"$flagd": {"flagKey": "...", "timestamp": ...}}` for JSON Logic dot notation - Added 6 tests covering timestamp injection, flagKey matching, and combined usage - Documented context enrichment in README with time-based and flag-specific examples **Example:** ```json { "targeting": { "if": [ { "and": [ {"==": [{"var": "$flagd.flagKey"}, "myFlag"]}, {">": [{"var": "$flagd.timestamp"}, 1704067200]} ] }, "enabled", "disabled" ] } } ``` ## Related Issue <!-- Issue linking handled separately by system --> ## Type of Change - [x] `feat`: New feature (minor version bump) - [ ] `fix`: Bug fix (patch version bump) - [ ] `docs`: Documentation only changes - [ ] `chore`: Maintenance tasks, dependency updates - [ ] `refactor`: Code refactoring without functional changes - [ ] `test`: Adding or updating tests - [ ] `ci`: CI/CD changes - [ ] `perf`: Performance improvements - [ ] `build`: Build system changes - [ ] `style`: Code style/formatting changes ## PR Title Format Title follows Conventional Commits format with breaking change indicator (`!`). ## Testing - [x] Unit tests added/updated - [x] Integration tests added/updated - [x] Manual testing performed - [x] All tests pass (`cargo test`) - 319 tests - [x] Code is formatted (`cargo fmt`) - [x] Clippy checks pass (`cargo clippy -- -D warnings`) - [x] WASM builds successfully (if applicable) ## Breaking Changes - [x] This PR includes breaking changes - [x] Documentation has been updated to reflect breaking changes - [ ] Migration guide included (if needed) **Breaking:** `flagKey` renamed to `$flagd.flagKey`. Targeting rules using `{"var": "flagKey"}` must change to `{"var": "$flagd.flagKey"}`. Previous implementation was non-compliant with specification. ## Additional Notes - Used `u64` for timestamp to avoid overflow - `targetingKey` unchanged (not part of `$flagd` namespace) - CodeQL: 0 alerts <!-- START COPILOT ORIGINAL PROMPT --> <details> <summary>Original prompt</summary> > > ---- > > *This section details on the original issue you should resolve* > > <issue_title>Support for `$flagd.timestamp` is missing based on provider specification</issue_title> > <issue_description>## Problem > > According to the provider specification (`docs/reference/specifications/providers.md`), in-process flagd providers should inject `$flagd.timestamp` (a unix timestamp in seconds of the time of evaluation) into the JsonLogic evaluation context. However, it appears that support for this property is missing in current implementations. > > ### Specification reference: > > | Property | Description | > > | ------------------ | ------------------------------------------------------- | > > | `$flagd.flagKey` | the identifier for the flag being evaluated | > > | `$flagd.timestamp` | a unix timestamp (in seconds) of the time of evaluation | > > ## Expected Behavior > - `$flagd. timestamp` should be injected into the JsonLogic evaluation context, as described in the provider specification. > > ## Observed Behavior > - Providers do not currently inject `$flagd.timestamp`, which may cause targeting rules relying on this property to fail or behave incorrectly. > > ## Steps to Reproduce > 1. Implement a custom targeting rule in JsonLogic that references `$flagd.timestamp`. > 2. Observe that the property is missing during flag evaluation. > > ## Additional context > - Provider specification file: [`docs/reference/specifications/providers.md`](https://github. com/open-feature/flagd/blob/main/docs/reference/specifications/providers.md) > > Please add support for `$flagd.timestamp` in all relevant provider implementations.</issue_description> > > ## Comments on the Issue (you are @copilot in this section) > > <comments> > </comments> > </details> <!-- START COPILOT CODING AGENT SUFFIX --> - Fixes #35 <!-- START COPILOT CODING AGENT TIPS --> --- 💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more [Copilot coding agent tips](https://gh.io/copilot-coding-agent-tips) in the docs. --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: aepfli <9987394+aepfli@users.noreply.github.com>
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Lines changed: 265 additions & 11 deletions

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‎README.md‎

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@@ -379,6 +379,61 @@ dealloc.apply(contextPtr, contextBytes.length);
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dealloc.apply(resultPtr, resultLen);
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```
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### Context Enrichment
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The evaluator automatically enriches the evaluation context with standard `$flagd` properties according to the [flagd provider specification](https://flagd.dev/reference/specifications/providers/#in-process-resolver). These properties are available in targeting rules via JSON Logic's `var` operator.
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**Injected Properties:**
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| Property | Type | Description | Example Access |
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|----------|------|-------------|----------------|
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| `$flagd.flagKey` | string | The key of the flag being evaluated | `{"var": "$flagd.flagKey"}` |
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| `$flagd.timestamp` | number | Unix timestamp in seconds at evaluation time | `{"var": "$flagd.timestamp"}` |
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| `targetingKey` | string | Key for consistent hashing (from context or empty string) | `{"var": "targetingKey"}` |
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**Example - Time-based Feature Flag:**
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```json
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{
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"flags": {
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"limitedTimeOffer": {
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"state": "ENABLED",
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"variants": {
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"active": true,
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"expired": false
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},
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"defaultVariant": "expired",
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"targeting": {
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"if": [
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{
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"and": [
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{">=": [{"var": "$flagd.timestamp"}, 1704067200]},
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{"<": [{"var": "$flagd.timestamp"}, 1735689600]}
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]
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},
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"active",
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"expired"
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]
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}
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}
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}
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}
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```
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**Example - Flag-specific Logic:**
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```json
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{
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"targeting": {
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"if": [
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{"==": [{"var": "$flagd.flagKey"}, "debugMode"]},
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"enabled",
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"disabled"
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]
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}
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}
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```
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**Note:** The `$flagd` properties are stored as a nested object in the evaluation context: `{"$flagd": {"flagKey": "...", "timestamp": ...}}`. This allows JSON Logic to access them using dot notation (e.g., `{"var": "$flagd.timestamp"}`).
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## JSON Schema Validation
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The evaluator automatically validates flag configurations against the official [flagd-schemas](https://github.com/open-feature/flagd-schemas) before storing them. This ensures that your flag configurations match the expected structure and catches errors early.

‎src/evaluation.rs‎

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@@ -180,28 +180,44 @@ impl EvaluationResult {
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/// Enriches the evaluation context with standard flagd fields.
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///
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/// According to the flagd specification, the evaluation context should include:
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/// - `flagKey`: The key of the flag being evaluated
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/// - `$flagd.flagKey`: The key of the flag being evaluated
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/// - `$flagd.timestamp`: Unix timestamp (in seconds) of the time of evaluation
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/// - `targetingKey`: A key used for consistent hashing (extracted from context or empty)
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/// - All custom fields from the original context
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///
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/// Note: `timestamp` is not included in this WASM implementation as it requires
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/// system time which may not be available in all WASM runtimes.
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/// The `$flagd` properties are stored as a nested object to support dot notation access
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/// in JSON Logic (e.g., `{"var": "$flagd.timestamp"}`).
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///
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/// # Arguments
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/// * `flag_key` - The key of the flag being evaluated
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/// * `context` - The original evaluation context
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///
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/// # Returns
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/// An enriched context with flagKey and targetingKey added
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/// An enriched context with $flagd properties and targetingKey added
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fn enrich_context(flag_key: &str, context: &Value) -> Value {
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let mut enriched = if let Some(obj) = context.as_object() {
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obj.clone()
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} else {
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Map::new()
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};
202203

203-
// Add flagKey
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enriched.insert("flagKey".to_string(), Value::String(flag_key.to_string()));
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// Get current Unix timestamp (seconds since epoch)
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// Note: SystemTime::now() is available in WASM runtimes that support WASI.
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// If system time is unavailable, we default to 0 (Unix epoch).
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// This allows targeting rules to detect the error condition by checking for timestamp == 0.
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let timestamp = std::time::SystemTime::now()
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.duration_since(std::time::UNIX_EPOCH)
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.map(|d| d.as_secs())
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.unwrap_or(0); // Default to 0 if system time is not available
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// Create $flagd object with nested properties
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let mut flagd_props = Map::new();
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flagd_props.insert("flagKey".to_string(), Value::String(flag_key.to_string()));
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// Store timestamp as u64 to avoid overflow issues. JSON can represent large numbers.
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flagd_props.insert("timestamp".to_string(), Value::Number(timestamp.into()));
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// Add $flagd object to context
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enriched.insert("$flagd".to_string(), Value::Object(flagd_props));
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// Ensure targetingKey exists (use existing or empty string)
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if !enriched.contains_key("targetingKey") {
@@ -644,13 +660,13 @@ mod tests {
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#[test]
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fn test_context_enrichment_with_flag_key() {
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let targeting = json!({
647-
"var": "flagKey"
663+
"var": "$flagd.flagKey"
648664
});
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let flag = create_test_flag(Some(targeting));
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let context = json!({});
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652668
let result = evaluate_flag(&flag, &context);
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// The targeting rule returns the flagKey variant name, which should be looked up
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// The targeting rule returns the $flagd.flagKey variant name, which should be looked up
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// Since "test_flag" is not a valid variant, it should fall back to default
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assert_eq!(result.variant, Some("off".to_string()));
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}
@@ -690,6 +706,92 @@ mod tests {
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assert_eq!(result.variant, Some("on".to_string()));
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}
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709+
#[test]
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fn test_context_enrichment_with_timestamp() {
711+
// Test that $flagd.timestamp is injected and is a valid unix timestamp
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let targeting = json!({
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"if": [
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{">": [{"var": "$flagd.timestamp"}, 0]},
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"on",
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"off"
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]
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});
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let flag = create_test_flag(Some(targeting));
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let context = json!({});
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let result = evaluate_flag(&flag, &context);
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// Should be "on" because timestamp should be > 0 (unless system time is before 1970)
724+
assert_eq!(result.value, json!(true));
725+
assert_eq!(result.variant, Some("on".to_string()));
726+
assert_eq!(result.reason, ResolutionReason::TargetingMatch);
727+
}
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#[test]
730+
fn test_context_enrichment_timestamp_is_numeric() {
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// Test that $flagd.timestamp is a number, not a string
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let targeting = json!({
733+
"var": "$flagd.timestamp"
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});
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let mut variants = HashMap::new();
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// Use numeric variants to verify timestamp is returned as a number
738+
variants.insert("timestamp".to_string(), json!(0));
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let flag = FeatureFlag {
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key: Some("test_flag".to_string()),
742+
state: "ENABLED".to_string(),
743+
default_variant: "timestamp".to_string(),
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variants,
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targeting: Some(targeting),
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metadata: HashMap::new(),
747+
};
748+
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let context = json!({});
750+
let result = evaluate_flag(&flag, &context);
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// The result should fall back to default because timestamp number
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// won't match "timestamp" string variant name
754+
assert_eq!(result.reason, ResolutionReason::Default);
755+
}
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#[test]
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fn test_context_enrichment_all_flagd_properties() {
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// Test that both $flagd.flagKey and $flagd.timestamp are present
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let targeting = json!({
761+
"if": [
762+
{
763+
"and": [
764+
{"==": [{"var": "$flagd.flagKey"}, "test_flag"]},
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{">": [{"var": "$flagd.timestamp"}, 0]}
766+
]
767+
},
768+
"success",
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"failure"
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]
771+
});
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let mut variants = HashMap::new();
774+
variants.insert("success".to_string(), json!("both-present"));
775+
variants.insert("failure".to_string(), json!("missing-properties"));
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let flag = FeatureFlag {
778+
key: Some("test_flag".to_string()),
779+
state: "ENABLED".to_string(),
780+
default_variant: "failure".to_string(),
781+
variants,
782+
targeting: Some(targeting),
783+
metadata: HashMap::new(),
784+
};
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786+
let context = json!({});
787+
let result = evaluate_flag(&flag, &context);
788+
789+
// Both conditions should be true, returning "success" variant
790+
assert_eq!(result.variant, Some("success".to_string()));
791+
assert_eq!(result.value, json!("both-present"));
792+
assert_eq!(result.reason, ResolutionReason::TargetingMatch);
793+
}
794+
693795
#[test]
694796
fn test_flag_without_key_returns_error() {
695797
let mut flag = create_test_flag(None);

‎src/lib.rs‎

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Original file line numberDiff line numberDiff line change
@@ -1610,7 +1610,7 @@ mod tests {
16101610
fn test_edge_case_targeting_with_flag_key_reference() {
16111611
clear_flag_state();
16121612

1613-
// Targeting rule that uses the flagKey field
1613+
// Targeting rule that uses the $flagd.flagKey field
16141614
let config = r#"{
16151615
"flags": {
16161616
"debugFlag": {
@@ -1622,7 +1622,7 @@ mod tests {
16221622
"defaultVariant": "off",
16231623
"targeting": {
16241624
"if": [
1625-
{"==": [{"var": "flagKey"}, "debugFlag"]},
1625+
{"==": [{"var": "$flagd.flagKey"}, "debugFlag"]},
16261626
"on",
16271627
"off"
16281628
]
@@ -1646,7 +1646,7 @@ mod tests {
16461646
context_bytes.len() as u32,
16471647
);
16481648

1649-
// Should match because flagKey is enriched in context
1649+
// Should match because $flagd.flagKey is enriched in context
16501650
assert_eq!(result.value, json!(true));
16511651
assert_eq!(result.variant, Some("on".to_string()));
16521652
assert_eq!(result.reason, ResolutionReason::TargetingMatch);
@@ -1732,6 +1732,103 @@ mod tests {
17321732
assert_eq!(result3.variant, Some("basic".to_string()));
17331733
}
17341734

1735+
#[test]
1736+
fn test_flagd_timestamp_in_targeting() {
1737+
clear_flag_state();
1738+
1739+
// Flag that uses $flagd.timestamp for time-based targeting
1740+
let config = r#"{
1741+
"flags": {
1742+
"timeBasedFlag": {
1743+
"state": "ENABLED",
1744+
"variants": {
1745+
"current": true,
1746+
"expired": false
1747+
},
1748+
"defaultVariant": "expired",
1749+
"targeting": {
1750+
"if": [
1751+
{">": [{"var": "$flagd.timestamp"}, 1000000000]},
1752+
"current",
1753+
"expired"
1754+
]
1755+
}
1756+
}
1757+
}
1758+
}"#;
1759+
1760+
let config_bytes = config.as_bytes();
1761+
update_state_internal(config_bytes.as_ptr(), config_bytes.len() as u32);
1762+
1763+
let context = r#"{}"#;
1764+
let context_bytes = context.as_bytes();
1765+
let flag_key = "timeBasedFlag";
1766+
let flag_key_bytes = flag_key.as_bytes();
1767+
1768+
let result = evaluate_internal(
1769+
flag_key_bytes.as_ptr(),
1770+
flag_key_bytes.len() as u32,
1771+
context_bytes.as_ptr(),
1772+
context_bytes.len() as u32,
1773+
);
1774+
1775+
// Current timestamp should be > 1000000000 (Sep 2001), so should get "current"
1776+
assert_eq!(result.value, json!(true));
1777+
assert_eq!(result.variant, Some("current".to_string()));
1778+
assert_eq!(result.reason, ResolutionReason::TargetingMatch);
1779+
}
1780+
1781+
#[test]
1782+
fn test_flagd_properties_are_injected() {
1783+
clear_flag_state();
1784+
1785+
// Flag that verifies both $flagd properties exist
1786+
let config = r#"{
1787+
"flags": {
1788+
"verifyFlag": {
1789+
"state": "ENABLED",
1790+
"variants": {
1791+
"verified": "properties-present",
1792+
"failed": "properties-missing"
1793+
},
1794+
"defaultVariant": "failed",
1795+
"targeting": {
1796+
"if": [
1797+
{
1798+
"and": [
1799+
{"==": [{"var": "$flagd.flagKey"}, "verifyFlag"]},
1800+
{">": [{"var": "$flagd.timestamp"}, 0]}
1801+
]
1802+
},
1803+
"verified",
1804+
"failed"
1805+
]
1806+
}
1807+
}
1808+
}
1809+
}"#;
1810+
1811+
let config_bytes = config.as_bytes();
1812+
update_state_internal(config_bytes.as_ptr(), config_bytes.len() as u32);
1813+
1814+
let context = r#"{}"#;
1815+
let context_bytes = context.as_bytes();
1816+
let flag_key = "verifyFlag";
1817+
let flag_key_bytes = flag_key.as_bytes();
1818+
1819+
let result = evaluate_internal(
1820+
flag_key_bytes.as_ptr(),
1821+
flag_key_bytes.len() as u32,
1822+
context_bytes.as_ptr(),
1823+
context_bytes.len() as u32,
1824+
);
1825+
1826+
// Both conditions should pass
1827+
assert_eq!(result.value, json!("properties-present"));
1828+
assert_eq!(result.variant, Some("verified".to_string()));
1829+
assert_eq!(result.reason, ResolutionReason::TargetingMatch);
1830+
}
1831+
17351832
// ============================================================================
17361833
// Type-specific WASM evaluation tests
17371834
// ============================================================================

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