feat: introduce flag merge behaviour

cmd/start.go

@@ -47,8 +47,9 @@ func init() {
 		"a", nil, "Sync provider arguments as key values separated by =")
 	flags.StringSliceP(
 		uriFlagName, "f", []string{}, "Set a sync provider uri to read data from, this can be a filepath,"+
-			"url (http and grpc) or FeatureFlagConfiguration. Using multiple providers is supported however if"+
-			" flag keys are duplicated across multiple sources it may lead to unexpected behavior. "+
+			"url (http and grpc) or FeatureFlagConfiguration. When flag keys are duplicated across multiple providers the "+
+			"merge priority follows the index of the flag arguments, as such flags from the uri at index 0 take the "+
+			"lowest precedence, with duplicated keys being overwritten by those from the uri at index 1. "+
 			"Please note that if you are using filepath, flagd only supports files with `.yaml/.yml/.json` extension.",
 	)
 	flags.StringP(

docs/configuration/flagd_start.md

@@ -21,7 +21,7 @@ flagd start [flags]
   -d, --socket-path string                  Flagd socket path. With grpc the service will become available on this address. With http(s) the grpc-gateway proxy will use this address internally.
   -y, --sync-provider string                DEPRECATED: Set a sync provider e.g. filepath or remote
   -a, --sync-provider-args stringToString   Sync provider arguments as key values separated by = (default [])
-  -f, --uri .yaml/.yml/.json                Set a sync provider uri to read data from, this can be a filepath,url (http and grpc) or FeatureFlagConfiguration. Using multiple providers is supported however if flag keys are duplicated across multiple sources it may lead to unexpected behavior. Please note that if you are using filepath, flagd only supports files with .yaml/.yml/.json extension.
+  -f, --uri .yaml/.yml/.json                Set a sync provider uri to read data from, this can be a filepath,url (http and grpc) or FeatureFlagConfiguration. When flag keys are duplicated across multiple providers the merge priority follows the index of the flag arguments, as such flags from the uri at index 0 take the lowest precedence, with duplicated keys being overwritten by those from the uri at index 1. Please note that if you are using filepath, flagd only supports files with .yaml/.yml/.json extension.
 ```
 
 ### Options inherited from parent commands

go.mod

@@ -3,9 +3,9 @@ module github.com/open-feature/flagd
 go 1.19
 
 require (
-	buf.build/gen/go/open-feature/flagd/bufbuild/connect-go v1.4.1-20221226184428-0dc62ff103b8.1
-	buf.build/gen/go/open-feature/flagd/grpc/go v1.2.0-20230207182158-c211472558c3.4
-	buf.build/gen/go/open-feature/flagd/protocolbuffers/go v1.28.1-20230207182158-c211472558c3.4
+	buf.build/gen/go/open-feature/flagd/bufbuild/connect-go v1.5.2-20230222100723-491ee098dd92.1
+	buf.build/gen/go/open-feature/flagd/grpc/go v1.2.0-20230222100723-491ee098dd92.4
+	buf.build/gen/go/open-feature/flagd/protocolbuffers/go v1.28.1-20230222100723-491ee098dd92.4
 	github.com/bufbuild/connect-go v1.5.2
 	github.com/cucumber/godog v0.12.6
 	github.com/diegoholiveira/jsonlogic/v3 v3.2.7
@@ -29,6 +29,7 @@ require (
 	go.opentelemetry.io/otel v1.13.0
 	go.opentelemetry.io/otel/exporters/prometheus v0.36.0
 	go.opentelemetry.io/otel/metric v0.36.0
+	go.opentelemetry.io/otel/sdk v1.13.0
 	go.opentelemetry.io/otel/sdk/metric v0.36.0
 	go.uber.org/zap v1.24.0
 	golang.org/x/net v0.7.0
@@ -45,7 +46,7 @@ require (
 require (
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect
-	github.com/common-nighthawk/go-figure v0.0.0-20200609044655-c4b36f998cf2 // indirect
+	github.com/common-nighthawk/go-figure v0.0.0-20210622060536-734e95fb86be // indirect
 	github.com/cpuguy83/go-md2man/v2 v2.0.2 // indirect
 	github.com/cucumber/gherkin-go/v19 v19.0.3 // indirect
 	github.com/cucumber/messages-go/v16 v16.0.1 // indirect
@@ -54,8 +55,8 @@ require (
 	github.com/evanphx/json-patch/v5 v5.6.0 // indirect
 	github.com/go-logr/logr v1.2.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
-	github.com/go-openapi/jsonpointer v0.19.5 // indirect
-	github.com/go-openapi/jsonreference v0.20.0 // indirect
+	github.com/go-openapi/jsonpointer v0.19.6 // indirect
+	github.com/go-openapi/jsonreference v0.20.2 // indirect
 	github.com/go-openapi/swag v0.22.3 // indirect
 	github.com/gofrs/uuid v4.2.0+incompatible // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
@@ -71,13 +72,13 @@ require (
 	github.com/hashicorp/golang-lru/v2 v2.0.1 // indirect
 	github.com/hashicorp/hcl v1.0.0 // indirect
 	github.com/imdario/mergo v0.3.13 // indirect
-	github.com/inconshreveable/mousetrap v1.0.1 // indirect
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/josharian/intern v1.0.0 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
-	github.com/klauspost/cpuid/v2 v2.1.1 // indirect
+	github.com/klauspost/cpuid/v2 v2.2.4 // indirect
 	github.com/magiconair/properties v1.8.7 // indirect
 	github.com/mailru/easyjson v0.7.7 // indirect
-	github.com/mattn/go-isatty v0.0.16 // indirect
+	github.com/mattn/go-isatty v0.0.17 // indirect
 	github.com/matttproud/golang_protobuf_extensions v1.0.4 // indirect
 	github.com/mitchellh/copystructure v1.2.0 // indirect
 	github.com/mitchellh/mapstructure v1.5.0 // indirect
@@ -90,8 +91,8 @@ require (
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/prometheus/client_model v0.3.0 // indirect
-	github.com/prometheus/common v0.37.0 // indirect
-	github.com/prometheus/procfs v0.8.0 // indirect
+	github.com/prometheus/common v0.40.0 // indirect
+	github.com/prometheus/procfs v0.9.0 // indirect
 	github.com/russross/blackfriday/v2 v2.1.0 // indirect
 	github.com/spf13/afero v1.9.3 // indirect
 	github.com/spf13/cast v1.5.0 // indirect
@@ -100,26 +101,25 @@ require (
 	github.com/subosito/gotenv v1.4.2 // indirect
 	github.com/xeipuuv/gojsonpointer v0.0.0-20190905194746-02993c407bfb // indirect
 	github.com/xeipuuv/gojsonreference v0.0.0-20180127040603-bd5ef7bd5415 // indirect
-	go.opentelemetry.io/otel/sdk v1.13.0 // indirect
 	go.opentelemetry.io/otel/trace v1.13.0 // indirect
 	go.uber.org/atomic v1.10.0 // indirect
-	go.uber.org/multierr v1.8.0 // indirect
-	golang.org/x/oauth2 v0.4.0 // indirect
+	go.uber.org/multierr v1.9.0 // indirect
+	golang.org/x/oauth2 v0.5.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
 	golang.org/x/term v0.5.0 // indirect
 	golang.org/x/text v0.7.0 // indirect
 	golang.org/x/time v0.3.0 // indirect
 	gomodules.xyz/jsonpatch/v2 v2.2.0 // indirect
 	google.golang.org/appengine v1.6.7 // indirect
-	google.golang.org/genproto v0.0.0-20230110181048-76db0878b65f // indirect
+	google.golang.org/genproto v0.0.0-20230221151758-ace64dc21148 // indirect
 	gopkg.in/inf.v0 v0.9.1 // indirect
 	gopkg.in/ini.v1 v1.67.0 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
 	k8s.io/apiextensions-apiserver v0.26.1 // indirect
 	k8s.io/component-base v0.26.1 // indirect
-	k8s.io/klog/v2 v2.80.1 // indirect
-	k8s.io/kube-openapi v0.0.0-20221123214604-86e75ddd809a // indirect
-	k8s.io/utils v0.0.0-20221128185143-99ec85e7a448 // indirect
+	k8s.io/klog/v2 v2.90.0 // indirect
+	k8s.io/kube-openapi v0.0.0-20230217203603-ff9a8e8fa21d // indirect
+	k8s.io/utils v0.0.0-20230220204549-a5ecb0141aa5 // indirect
 	sigs.k8s.io/json v0.0.0-20221116044647-bc3834ca7abd // indirect
 	sigs.k8s.io/structured-merge-diff/v4 v4.2.3 // indirect
 	sigs.k8s.io/yaml v1.3.0 // indirect