Let a .v* extension config key apply to any extension version

config.go

@@ -0,0 +1,39 @@
+// SPDX-FileCopyrightText: Copyright The Moby Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package extensions
+
+import "fmt"
+
+// Config is parsed per-extension configuration delivered by id to Init or the
+// out-of-process startup handshake.
+type Config = map[string]any
+
+// ValidateExtensionConfigKey reports whether key can key extension
+// configuration.
+// A key is either a full extension id such as org.example.myext.v1, or an
+// extension name without a version, such as org.example.myext, which applies
+// to every version of that extension.
+func ValidateExtensionConfigKey(key ExtensionID) error {
+	if ValidateExtensionID(key) != nil && !validExtensionName(string(key)) {
+		return fmt.Errorf("invalid extension config key %q: want an extension id like org.example.myext.v1, or a name like org.example.myext for any version", key)
+	}
+
+	return nil
+}
+
+// LookupConfig returns the configuration for extension id from configs.
+// An entry keyed by id takes precedence over one keyed by the extension name,
+// which is id without its version.
+func LookupConfig(configs map[ExtensionID]Config, id ExtensionID) Config {
+	if config, ok := configs[id]; ok {
+		return config
+	}
+
+	name, ok := cutExtensionVersion(id)
+	if !ok {
+		return nil
+	}
+
+	return configs[ExtensionID(name)]
+}

config_test.go

@@ -0,0 +1,66 @@
+// SPDX-FileCopyrightText: Copyright The Moby Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package extensions
+
+import (
+	"testing"
+
+	"gotest.tools/v3/assert"
+)
+
+func TestValidateExtensionConfigKey(t *testing.T) {
+	valid := []ExtensionID{
+		"org.example.myext.v1",
+		"org.example.myext",
+		"org.example.s3-volume",
+		"org.example.v1",
+	}
+	for _, key := range valid {
+		if err := ValidateExtensionConfigKey(key); err != nil {
+			t.Errorf("ValidateExtensionConfigKey(%q) = %v, want nil", key, err)
+		}
+	}
+
+	invalid := []ExtensionID{
+		"",
+		"foo",                     // only one name segment
+		"org.example.myext.v*",    // wildcard
+		"org.example.myext.*",     // wildcard
+		"org.example.myext.v1.v2", // name ends in a version
+		"Org.Example.myext",       // uppercase
+		"org.example/evil",        // path separator
+	}
+	for _, key := range invalid {
+		if err := ValidateExtensionConfigKey(key); err == nil {
+			t.Errorf("ValidateExtensionConfigKey(%q) = nil, want error", key)
+		}
+	}
+}
+
+func TestLookupConfig(t *testing.T) {
+	exact := Config{"source": "exact"}
+	anyVersion := Config{"source": "any version"}
+	configs := map[ExtensionID]Config{
+		"org.example.foo.v1": exact,
+		"org.example.foo":    anyVersion,
+		"org.example.bar.v1": {"source": "bar"},
+	}
+
+	for _, tc := range []struct {
+		name string
+		id   ExtensionID
+		want Config
+	}{
+		{name: "exact id takes precedence", id: "org.example.foo.v1", want: exact},
+		{name: "name key covers other versions", id: "org.example.foo.v2", want: anyVersion},
+		{name: "other extension without a key", id: "org.example.baz.v1", want: nil},
+		{name: "exact key does not cover other versions", id: "org.example.bar.v2", want: nil},
+		{name: "name prefix does not match", id: "org.example.foobar.v1", want: nil},
+		{name: "name key does not cover nested names", id: "org.example.foo.runtime.v1", want: nil},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			assert.DeepEqual(t, LookupConfig(configs, tc.id), tc.want)
+		})
+	}
+}

core.go

@@ -112,20 +112,70 @@ func ValidatePointID(id PointID) error {
 	return nil
 }
 
-// extensionIDPattern requires a lowercase reverse-DNS name with a mandatory vN
-// version. The version is a namespace element, not a semantic version: changing
-// com.foo.v1 to com.foo.v2 creates a new extension, binary, and configuration.
+// cutExtensionVersion splits id into its name and its mandatory ".vN" version.
+// The version is a namespace element, not a semantic version: changing
+// com.foo.v1 to com.foo.v2 creates a new extension and binary.
+func cutExtensionVersion(id ExtensionID) (name string, ok bool) {
+	i := strings.LastIndexByte(string(id), '.')
+	if i < 0 || !isExtensionVersion(string(id[i+1:])) {
+		return "", false
+	}
+
+	return string(id[:i]), true
+}
+
+// isExtensionVersion reports whether segment is a version such as v1.
+func isExtensionVersion(segment string) bool {
+	digits, ok := strings.CutPrefix(segment, "v")
+	if !ok || digits == "" {
+		return false
+	}
+
+	for _, r := range digits {
+		if r < '0' || r > '9' {
+			return false
+		}
+	}
+
+	return true
+}
+
+// validExtensionName reports whether name is a lowercase reverse-DNS extension
+// name: an extension id without its version.
 // The restricted characters also make the id safe as a config key and filename.
-var extensionIDPattern = lazyRegexp(`^[a-z0-9]+(-[a-z0-9]+)*(\.[a-z0-9]+(-[a-z0-9]+)*)+\.v[0-9]+$`)
+// A name must not end in a version itself, so a configuration key is either an
+// extension id or an extension name, never both.
+func validExtensionName(name string) bool {
+	segments := strings.Split(name, ".")
+	if len(segments) < 2 || isExtensionVersion(segments[len(segments)-1]) {
+		return false
+	}
+
+	for _, segment := range segments {
+		if segment == "" || segment[0] == '-' || segment[len(segment)-1] == '-' || strings.Contains(segment, "--") {
+			return false
+		}
+
+		for _, r := range segment {
+			if (r < 'a' || r > 'z') && (r < '0' || r > '9') && r != '-' {
+				return false
+			}
+		}
+	}
+
+	return true
+}
 
 // ValidateExtensionID reports whether id is well-formed before it is used as a
 // configuration key or binary name.
 func ValidateExtensionID(id ExtensionID) error {
 	if id == "" {
 		return errors.New("extension id is required")
 	}
-	if !extensionIDPattern().MatchString(string(id)) {
-		return fmt.Errorf("invalid extension id %q: want a versioned reverse-DNS name like org.example.myext.v1, lowercase, no path-hostile characters", id)
+
+	name, ok := cutExtensionVersion(id)
+	if !ok || !validExtensionName(name) {
+		return fmt.Errorf("invalid extension id %q: want a versioned reverse-DNS name like org.example.myext.v1, lowercase, no path-hostile characters, with a name that does not end in a version", id)
 	}
 	return nil
 }
@@ -306,10 +356,6 @@ func RegisterAll(registrar Registrar, exts ...Extension) error {
 	return nil
 }
 
-// Config is parsed per-extension configuration delivered by id to Init or the
-// out-of-process startup handshake.
-type Config = map[string]any
-
 // Extension is a host-managed extension declaration.
 type Extension interface {
 	// Declaration returns the extension's id, providers, dependencies, and

core_test.go

@@ -104,6 +104,7 @@ func TestValidateExtensionID(t *testing.T) {
 		"org.example.a b.v1",         // whitespace
 		"org..example.v1",            // empty segment
 		"org.example.under_score.v1", // underscore not allowed in extension ids
+		"org.example.v1.v2",          // name ends in a version, so the key org.example.v1 would be ambiguous
 	}
 	for _, id := range invalid {
 		if err := ValidateExtensionID(id); err == nil {

docs/AUTHORING.md

@@ -331,7 +331,7 @@ func (b *Bridge) Declaration() extensions.Declaration {
 ```
 
 `Init` receives the extension config and a resolver.
-The application supplies config keyed by id through `host.WithExtensionConfig`; declare dependencies and conflicts in the declaration.
+The application supplies config keyed by id, or by the id without its version for every version, through `host.WithExtensionConfig`; declare dependencies and conflicts in the declaration.
 The broker initializes dependencies before dependents.
 
 ### Retain dependencies for later calls
@@ -414,11 +414,17 @@ Configure extensions when constructing the Host:
 ```go
 host.WithExtensionConfig(map[extensions.ExtensionID]extensions.Config{
 	"com.example.myext.v1": {"some_key": "value"},
+	"com.example.other":    {"some_key": "value"},
 }),
 ```
 
 The same entry reaches an in-process `Init` or a separate binary through the startup handshake.
+A key without the version, such as `com.example.other`, applies to every version of that extension.
+It matches only that name: `com.example.other` does not reach `com.example.other.runtime.v1`.
+A key with the full id, such as `com.example.other.v2`, takes precedence over it.
+Because each version is a separate extension, a versionless entry must suit the configuration format of every version it reaches.
 The application chooses how to read and validate this configuration; the framework does not read `daemon.json`.
+The Host does not validate keys and silently ignores one that matches no extension; check their format with `extensions.ValidateExtensionConfigKey`.
 
 ### Run in-process
 
@@ -509,7 +515,7 @@ See the [lifecycle limitations](./DESIGN.md#resolution-ordering-and-lifecycle).
 - Discover binaries with `host.WithDirs` and provide socket storage with `host.WithRuntimeDir`.
 - Wire internal calls to binaries with `host.WithClientProviders`.
 - Wire calls from binaries to Host providers with `host.WithDependencyProviders` and SDK `Server.Depends`.
-- Supply configuration by extension id with `host.WithExtensionConfig`.
+- Supply configuration by extension id, or by the id without its version for every version, with `host.WithExtensionConfig`.
 - Resolve Points through the Host and call their contract helpers.
 - Restrict internal providers with `host.WithProviderPolicy` using ordinary Point IDs.
 - Offer implemented Points with `servicev0.Offer`, authorize publication through policy on `servicev0.Point.ID()`, and supply `host.WithPointServers` for in-process offers.

docs/DESIGN.md

@@ -36,7 +36,9 @@ These names are distinct:
   The id is the binary name, configuration key, dependency name, and named-lookup selector, not an interface name.
   Registration rejects invalid ids.
   Its version is a namespace element, not a semantic version, and is independent of point versions.
-  Thus `com.foo.v1` and `com.foo.v2` are different extensions, binaries, and configurations that can coexist.
+  Thus `com.foo.v1` and `com.foo.v2` are different extensions and binaries that can coexist.
+  Their configuration is separate unless the application supplies a `com.foo` key, which applies to every version without an entry keyed by its full id.
+  The name before the version must not end in a version itself, so `com.foo.v1.v2` is invalid and a key is never both an id and a name.
 - **Extension identity** is the logical extension id plus the host-attested origin `builtin` or `executable`.
   Registration rejects an empty or unknown origin, an invalid identity id, or an identity id that differs from the declaration id.
   Providers and Host policy receive this validated identity.
@@ -169,7 +171,7 @@ The binary name is its extension id (`<id>.exe` on Windows), and the daemon laun
 Startup proceeds as follows:
 
 1. The daemon writes JSON to stdin with `endpoint`, `protocolVersion`, `config`, and, when dependencies are offered, `callbackEndpoint`.
-   The current protocol version is `1`; `config` is the entry supplied through `host.WithExtensionConfig` for the id.
+   The current protocol version is `1`; `config` is the entry that `extensions.LookupConfig` selects for the id from `host.WithExtensionConfig`.
 2. The SDK listens on the supplied Unix socket, then writes exactly `ready\n` to stdout.
    Stdout is reserved for this line: any earlier output corrupts the handshake and fails launch.
    The daemon also drains later stdout so it cannot block the process.

host/host.go

@@ -189,6 +189,9 @@ func WithReservedServices(services ...string) Option {
 }
 
 // WithExtensionConfig sets configuration keyed by extension id.
+// A key without the version, such as org.example.myext, applies to every
+// version of that extension; a key with the full id takes precedence.
+// See [extensions.LookupConfig].
 // The outer map is copied when this option is created, while configuration
 // values are shared.
 func WithExtensionConfig(config map[extensions.ExtensionID]extensions.Config) Option {

internal/broker/broker.go

@@ -108,7 +108,8 @@ func (b *Broker) checkConflicts(ext extensions.Declaration) error {
 }
 
 // Init resolves dependencies and initializes all registered extensions in
-// order, delivering each its configuration from configs (keyed by extension id).
+// order, delivering each its configuration from configs, as selected by
+// [extensions.LookupConfig].
 func (b *Broker) Init(ctx context.Context, configs map[extensions.ExtensionID]extensions.Config) error {
 	b.mu.Lock()
 	resolved, err := b.resolveOrder()
@@ -131,7 +132,7 @@ func (b *Broker) Init(ctx context.Context, configs map[extensions.ExtensionID]ex
 		}
 		// Init may resolve providers, so do not hold the lock across the callback.
 		if initFn != nil {
-			if err := initFn(ctx, configs[id], b); err != nil {
+			if err := initFn(ctx, extensions.LookupConfig(configs, id), b); err != nil {
 				return fmt.Errorf("initialize extension %q: %w", id, err)
 			}
 		}

internal/launcher/launcher.go

@@ -32,8 +32,9 @@ type Launcher struct {
 	RuntimeDir      string
 	ReadyTimeout    time.Duration
 	ShutdownTimeout time.Duration
-	// ExtensionConfig holds configuration keyed by extension id. The selected
-	// entry is delivered over the startup handshake.
+	// ExtensionConfig holds configuration keyed by extension id, or by an id
+	// without its version. The entry selected by [extensions.LookupConfig] is
+	// delivered over the startup handshake.
 	ExtensionConfig map[extensions.ExtensionID]extensions.Config
 	// CallbackEndpoint is the socket where the host serves dependencies.
 	CallbackEndpoint string
@@ -129,7 +130,7 @@ func (l Launcher) Launch(ctx context.Context, bin string) (*Launched, error) {
 	startup := sdk.StartupConfig{
 		Endpoint:         endpoint,
 		ProtocolVersion:  sdk.ProtocolVersion,
-		Config:           l.ExtensionConfig[extensions.ExtensionID(name)],
+		Config:           extensions.LookupConfig(l.ExtensionConfig, extensions.ExtensionID(name)),
 		CallbackEndpoint: l.CallbackEndpoint,
 	}
 	launchCtx, cancel := context.WithTimeout(ctx, readyTimeout)