feat: OpenFeature provider for Elixir

.github/workflows/checks.yml

@@ -47,6 +47,44 @@ jobs:
           mix docs --warnings-as-errors
           mix hex.build
 
+  openfeature:
+    name: OpenFeature with Elixir ${{ matrix.elixir }} and OTP ${{ matrix.otp }}
+    runs-on: ubuntu-latest
+    timeout-minutes: 25
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - elixir: "1.15.8"
+            otp: "26.2"
+          - elixir: "1.20.3"
+            otp: "29.0"
+
+    steps:
+      - uses: actions/checkout@v7
+      - uses: erlef/setup-beam@v1.24.1
+        with:
+          elixir-version: ${{ matrix.elixir }}
+          otp-version: ${{ matrix.otp }}
+      - name: Install provider dependencies
+        working-directory: openfeature
+        run: FEATUREVISOR_OPENFEATURE_PATH=.. mix deps.get
+      - name: Compile provider without warnings
+        working-directory: openfeature
+        run: FEATUREVISOR_OPENFEATURE_PATH=.. mix compile --warnings-as-errors
+      - name: Test provider
+        working-directory: openfeature
+        run: FEATUREVISOR_OPENFEATURE_PATH=.. mix test
+      - name: Format, static analysis, documentation, and package
+        if: matrix.elixir == '1.20.3'
+        working-directory: openfeature
+        run: |
+          mix format --check-formatted
+          FEATUREVISOR_OPENFEATURE_PATH=.. mix credo --strict
+          FEATUREVISOR_OPENFEATURE_PATH=.. mix dialyzer
+          FEATUREVISOR_OPENFEATURE_PATH=.. mix docs --warnings-as-errors
+          env -u FEATUREVISOR_OPENFEATURE_PATH mix hex.build
+
   example:
     name: Featurevisor example 1
     runs-on: ubuntu-latest

.github/workflows/publish.yml

@@ -24,9 +24,17 @@ jobs:
           node-version: 24
           package-manager-cache: false
       - name: Install dependencies
-        run: mix deps.get
-      - name: Verify tag matches package version
-        run: test "${GITHUB_REF_NAME#v}" = "$(mix run --no-start --no-compile -e 'IO.write(Mix.Project.config()[:version])')"
+        run: |
+          mix deps.get
+          cd openfeature
+          FEATUREVISOR_OPENFEATURE_PATH=.. mix deps.get
+      - name: Verify tag matches package versions
+        run: |
+          version="${GITHUB_REF_NAME#v}"
+          base_version=$(mix run --no-start --no-compile -e 'IO.write(Mix.Project.config()[:version])')
+          provider_version=$(cd openfeature && FEATUREVISOR_OPENFEATURE_PATH=.. mix run --no-start --no-compile -e 'IO.write(Mix.Project.config()[:version])')
+          test "$version" = "$base_version"
+          test "$base_version" = "$provider_version"
       - name: Run checks
         run: make check
       - name: Set up Featurevisor example 1 project
@@ -48,7 +56,50 @@ jobs:
           tar -tf featurevisor-*.tar | grep '^contents.tar.gz$'
         env:
           HEX_API_KEY: ${{ secrets.HEX_API_KEY }}
-      - name: Publish to Hex.pm
-        run: mix hex.publish --yes
+      - name: Publish base package to Hex.pm
+        shell: bash
+        run: |
+          version="${GITHUB_REF_NAME#v}"
+          if curl --fail --silent --show-error "https://hex.pm/api/packages/featurevisor/releases/$version" >/dev/null; then
+            echo "featurevisor $version is already published"
+          else
+            mix hex.publish --yes
+          fi
+        env:
+          HEX_API_KEY: ${{ secrets.HEX_API_KEY }}
+      - name: Wait for base package
+        shell: bash
+        run: |
+          version="${GITHUB_REF_NAME#v}"
+          for attempt in {1..18}; do
+            if curl --fail --silent --show-error "https://hex.pm/api/packages/featurevisor/releases/$version" >/dev/null; then
+              exit 0
+            fi
+            sleep 10
+          done
+          echo "featurevisor $version did not become available on Hex.pm" >&2
+          exit 1
+      - name: Publish OpenFeature provider package to Hex.pm
+        shell: bash
+        working-directory: openfeature
+        run: |
+          version="${GITHUB_REF_NAME#v}"
+          if curl --fail --silent --show-error "https://hex.pm/api/packages/featurevisor_openfeature/releases/$version" >/dev/null; then
+            echo "featurevisor_openfeature $version is already published"
+          else
+            resolved=false
+            for attempt in {1..18}; do
+              if env -u FEATUREVISOR_OPENFEATURE_PATH mix deps.get; then
+                resolved=true
+                break
+              fi
+              sleep 10
+            done
+            test "$resolved" = true
+            env -u FEATUREVISOR_OPENFEATURE_PATH mix hex.publish --dry-run --yes
+            env -u FEATUREVISOR_OPENFEATURE_PATH mix hex.build
+            tar -tf featurevisor_openfeature-*.tar | grep '^contents.tar.gz$'
+            env -u FEATUREVISOR_OPENFEATURE_PATH mix hex.publish --yes
+          fi
         env:
           HEX_API_KEY: ${{ secrets.HEX_API_KEY }}

Makefile

@@ -1,10 +1,13 @@
 FEATUREVISOR_PROJECT ?= ../featurevisor/examples/example-1
 
-.PHONY: deps format format-check compile test credo dialyzer docs package check escript test-example-1
+.PHONY: deps deps-openfeature format format-check compile test test-openfeature credo dialyzer docs docs-openfeature package package-openfeature check check-base check-openfeature escript test-example-1
 
 deps:
 	mix deps.get
 
+deps-openfeature:
+	cd openfeature && FEATUREVISOR_OPENFEATURE_PATH=.. mix deps.get
+
 format:
 	mix format
 
@@ -17,6 +20,9 @@ compile:
 test:
 	mix test
 
+test-openfeature:
+	cd openfeature && FEATUREVISOR_OPENFEATURE_PATH=.. mix test
+
 credo:
 	mix credo --strict
 
@@ -26,13 +32,30 @@ dialyzer:
 docs:
 	mix docs --warnings-as-errors
 
+docs-openfeature:
+	cd openfeature && FEATUREVISOR_OPENFEATURE_PATH=.. mix docs --warnings-as-errors
+
 package:
 	mix hex.build
 
+package-openfeature:
+	cd openfeature && env -u FEATUREVISOR_OPENFEATURE_PATH mix hex.build
+
 escript:
 	mix escript.build
 
-check: format-check compile test credo dialyzer docs package
+check-base: format-check compile test credo dialyzer docs package
+
+check-openfeature: deps-openfeature
+	cd openfeature && mix format --check-formatted
+	cd openfeature && FEATUREVISOR_OPENFEATURE_PATH=.. mix compile --warnings-as-errors
+	cd openfeature && FEATUREVISOR_OPENFEATURE_PATH=.. mix test
+	cd openfeature && FEATUREVISOR_OPENFEATURE_PATH=.. mix credo --strict
+	cd openfeature && FEATUREVISOR_OPENFEATURE_PATH=.. mix dialyzer
+	cd openfeature && FEATUREVISOR_OPENFEATURE_PATH=.. mix docs --warnings-as-errors
+	cd openfeature && env -u FEATUREVISOR_OPENFEATURE_PATH mix hex.build
+
+check: check-base check-openfeature
 
 test-example-1: test escript
 	./featurevisor test --projectDirectoryPath=$(FEATUREVISOR_PROJECT) --onlyFailures

README.md

@@ -35,6 +35,7 @@ The SDK supports concurrent evaluations, structured diagnostics, lifecycle modul
 - [Modules](#modules)
 - [Child instance](#child-instance)
 - [Close](#close)
+- [OpenFeature](#openfeature)
 - [CLI usage](#cli-usage)
   - [Test](#test)
   - [Benchmark](#benchmark)
@@ -52,7 +53,7 @@ Add `featurevisor` to your dependencies in `mix.exs`:
 ```elixir
 def deps do
   [
-    {:featurevisor, "~> 1.0"}
+    {:featurevisor, "~> 1.2"}
   ]
 end
 ```
@@ -446,6 +447,78 @@ Close invokes module close callbacks and removes listeners, diagnostic subscript
 
 Do not call `close/1` directly for a supervised instance. Stop its supervisor or remove its child instead. A closed handle evaluates against an empty datafile, so flags return `false`, variations and variables return `nil`, and the revision returns `"unknown"`.
 
+## OpenFeature
+
+The OpenFeature provider is published as a separate Hex package. Applications
+that only use the Featurevisor SDK do not install or compile OpenFeature or the
+provider code.
+
+```elixir
+def deps do
+  [
+    {:featurevisor, "~> 1.2"},
+    {:featurevisor_openfeature, "~> 1.2"},
+    {:open_feature, "~> 0.1.3"}
+  ]
+end
+```
+
+Create a provider that owns its Featurevisor instance:
+
+```elixir
+provider =
+  FeaturevisorOpenFeature.Provider.new(
+    featurevisor_options: %{datafile: datafile}
+  )
+
+{:ok, provider} = OpenFeature.set_provider(provider)
+client = OpenFeature.get_client()
+
+enabled =
+  OpenFeature.Client.get_boolean_value(client, "checkout", false,
+    context: %{"targetingKey" => "user-123"}
+  )
+```
+
+You can also pass an existing Featurevisor instance. The provider borrows it
+and does not close it:
+
+```elixir
+provider = FeaturevisorOpenFeature.Provider.new(featurevisor: f)
+```
+
+OpenFeature uses one flag key while Featurevisor supports flags, variations,
+feature variables, and global variables:
+
+| OpenFeature key | Featurevisor evaluation |
+| --- | --- |
+| `checkout` | Flag for feature `checkout` |
+| `checkout:variation` | Variation for feature `checkout` |
+| `checkout:title` | Variable `title` inside feature `checkout` |
+| `variable:supportEmail` | Global variable `supportEmail` |
+
+`targeting_key_field`, `key_separator`, `variation_key`, and
+`global_variable_prefix` customize this mapping. The targeting key maps to
+`userId` by default. The global variable prefix defaults to `variable` and
+cannot contain the separator.
+
+The official OpenFeature Elixir SDK represents evaluation context as a map. The
+provider accepts `"targetingKey"`, `"targeting_key"`, or `:targeting_key` and
+copies its string value to the configured Featurevisor targeting field.
+
+The provider implements boolean, string, number, and map resolution.
+Featurevisor evaluation reasons, variation values, revision, schema version,
+rule keys, bucket information, and override information are mapped to
+OpenFeature resolution details and flag metadata. Missing definitions, type
+mismatches, and invalid datafiles use standard OpenFeature errors. Replacing an
+invalid datafile with a valid one recovers the provider.
+
+The OpenFeature Elixir SDK does not currently expose provider tracking.
+Featurevisor modules and diagnostics continue to run inside the Featurevisor
+instance.
+
+See the [OpenFeature provider guide](https://featurevisor.com/docs/sdks/openfeature/) for the shared key convention and providers for other languages.
+
 ## CLI usage
 
 Build the escript from this repository:
@@ -522,7 +595,7 @@ make test-example-1
 
 The integration target executes all expanded `example-1` assertions, including Target datafiles, through the Elixir evaluator.
 
-`make check` remains the fast package gate. The separate `make test-example-1` target requires the sibling Featurevisor monorepo, so checks and publishing workflows run that integration explicitly after the package gate.
+`make check` verifies both the base SDK and OpenFeature provider. The separate `make test-example-1` target requires the sibling Featurevisor monorepo, so checks and publishing workflows run that integration explicitly after the package gate.
 
 ## Publishing
 
@@ -533,7 +606,11 @@ make check
 mix hex.publish --dry-run
 ```
 
-The release workflow verifies the tag, package contents, documentation, and `example-1` integration before publishing to Hex.pm.
+The repository publishes `featurevisor` and `featurevisor_openfeature` with the same version. The release workflow verifies the tag, package contents, documentation, and `example-1` integration, then publishes the base package before the provider package.
+
+Hex can only resolve the provider's exact base package dependency after the
+matching `featurevisor` release is visible. The workflow waits for that release
+before it performs the final provider dry run and publication.
 
 The published Hex package intentionally includes runtime source, `mix.exs`, the README, and the licence. Tests and the conformance fixture remain repository verification assets and are not shipped to consumers.
 

mix.exs

@@ -1,7 +1,7 @@
 defmodule Featurevisor.MixProject do
   use Mix.Project
 
-  @version "1.1.0"
+  @version "1.2.0"
   @source_url "https://github.com/featurevisor/featurevisor-elixir"
 
   def project do

openfeature/.formatter.exs

@@ -0,0 +1,3 @@
+[
+  inputs: ["{mix,.formatter}.exs", "{lib,test}/**/*.{ex,exs}"]
+]

openfeature/.gitignore

@@ -0,0 +1,20 @@
+/_build/
+/cover/
+/deps/
+/doc/
+/erl_crash.dump
+*.ez
+/featurevisor_openfeature-*.tar
+/.elixir_ls/
+/.lexical/
+/.vscode/
+/.idea/
+/.DS_Store
+/.env
+/.env.*
+!/.env.example
+*.pem
+*.key
+*.p12
+*.pfx
+*.secret

openfeature/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Fahad Heylaal
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.