[Open Screen] Create a //discovery:public target

This creates a :public GN target for other Open Screen modules (or
embedders) to depend on.

It also:
- Consolidates the DNS-SD public APIs.
- Adds DEPS rules to enforce use of public headers.
- Adds DEPS rules to enforce layering inside of //discovery (with some
  exceptions).
- Adjusts deps for the //discovery targets.

Bug: b/179705382
Change-Id: Ice48b8d8937d3c68351d693b348a2928f14dfb4b
Reviewed-on: https://chromium-review.googlesource.com/c/openscreen/+/3032947
Commit-Queue: mark a. foltz <mfoltz@chromium.org>
Reviewed-by: Ryan Keane <rwkeane@google.com>

11 files changed, 63 insertions, 51 deletions

diff --git a/BUILD.gn b/BUILD.gn
index 95ab0c96..7d26028a 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -16,7 +16,6 @@ group("gn_all") {
     "cast/sender:channel",
     "cast/streaming:receiver",
     "cast/streaming:sender",
-    "discovery:common",
     "discovery:dnssd",
     "discovery:mdns",
     "discovery:public",
diff --git a/DEPS b/DEPS
index 2fb5f1ba..64d06374 100644
--- a/DEPS
+++ b/DEPS
@@ -226,6 +226,13 @@ include_rules = [
   '+testing/util',
   '+third_party',
 
+  # Inter-module dependencies must be through public APIs.
+  '-discovery',
+  '+discovery/common',
+  '+discovery/dnssd/public',
+  '+discovery/mdns/public',
+  '+discovery/public',
+
   # Don't include abseil from the root so the path can change via include_dirs
   # rules when in Chromium.
   '-third_party/abseil',
diff --git a/cast/common/BUILD.gn b/cast/common/BUILD.gn
index 750d72ea..154d436e 100644
--- a/cast/common/BUILD.gn
+++ b/cast/common/BUILD.gn
@@ -88,11 +88,10 @@ source_set("public") {
   ]
 
   deps = [
-    "../../discovery:dnssd",
-    "../../discovery:mdns",
     "../../discovery:public",
     "../../platform",
     "../../third_party/abseil",
+    "../../util",
   ]
 }
 
@@ -107,7 +106,6 @@ if (!build_with_chromium) {
     deps = [
       ":public",
       "../../discovery:dnssd",
-      "../../discovery:mdns",
       "../../discovery:public",
       "../../platform:standalone_impl",
       "../../testing/util",
@@ -132,8 +130,7 @@ source_set("test_helpers") {
     ":certificate",
     ":channel",
     ":public",
-    "../../discovery:dnssd",
-    "../../discovery:mdns",
+    "../../discovery:public",
     "../../platform:test",
     "../../testing/util",
     "../../third_party/abseil",
diff --git a/cast/standalone_receiver/BUILD.gn b/cast/standalone_receiver/BUILD.gn
index 956a1a71..23d394ac 100644
--- a/cast/standalone_receiver/BUILD.gn
+++ b/cast/standalone_receiver/BUILD.gn
@@ -23,7 +23,7 @@ if (!build_with_chromium) {
   ]
 
   shared_deps = [
-    "../../discovery:common",
+    "../../discovery:dnssd",
     "../../discovery:public",
     "../../platform:standalone_impl",
     "../common:public",
diff --git a/discovery/BUILD.gn b/discovery/BUILD.gn
index 11598c8f..0a747258 100644
--- a/discovery/BUILD.gn
+++ b/discovery/BUILD.gn
@@ -5,20 +5,32 @@
 import("//build_overrides/build.gni")
 import("../testing/libfuzzer/fuzzer_test.gni")
 
-source_set("common") {
+source_set("public") {
   sources = [
     "common/config.h",
     "common/reporting_client.h",
+    "dnssd/public/dns_sd_instance.cc",
+    "dnssd/public/dns_sd_instance.h",
+    "dnssd/public/dns_sd_instance_endpoint.cc",
+    "dnssd/public/dns_sd_instance_endpoint.h",
+    "dnssd/public/dns_sd_publisher.h",
+    "dnssd/public/dns_sd_querier.h",
+    "dnssd/public/dns_sd_service.h",
+    "dnssd/public/dns_sd_txt_record.cc",
+    "dnssd/public/dns_sd_txt_record.h",
+    "mdns/public/mdns_constants.h",
+    "mdns/public/mdns_service.cc",
+    "mdns/public/mdns_service.h",
+    "public/dns_sd_service_factory.h",
+    "public/dns_sd_service_publisher.h",
+    "public/dns_sd_service_watcher.h",
   ]
-
+  public_deps = [ "../platform" ]
   deps = [ "../util" ]
-
-  public_deps = [
-    "../platform",
-    "../third_party/abseil",
-  ]
 }
 
+# TODO(https://issuetracker.google.com/issues/194234872):
+# Move implementation files to impl/
 source_set("mdns") {
   sources = [
     "mdns/mdns_domain_confirmed_provider.h",
@@ -47,21 +59,16 @@ source_set("mdns") {
     "mdns/mdns_trackers.h",
     "mdns/mdns_writer.cc",
     "mdns/mdns_writer.h",
-    "mdns/public/mdns_constants.h",
-    "mdns/public/mdns_service.cc",
-    "mdns/public/mdns_service.h",
   ]
 
-  deps = [ "../util" ]
-
-  public_deps = [
-    ":common",
+  deps = [
+    ":public",
     "../platform",
     "../third_party/abseil",
+    "../util",
   ]
 }
 
-# TODO(issuetracker.google.com/179705382): Separate out a public target.
 source_set("dnssd") {
   sources = [
     "dnssd/impl/conversion_layer.cc",
@@ -82,34 +89,12 @@ source_set("dnssd") {
     "dnssd/impl/service_instance.h",
     "dnssd/impl/service_key.cc",
     "dnssd/impl/service_key.h",
-    "dnssd/public/dns_sd_instance.cc",
-    "dnssd/public/dns_sd_instance.h",
-    "dnssd/public/dns_sd_instance_endpoint.cc",
-    "dnssd/public/dns_sd_instance_endpoint.h",
-    "dnssd/public/dns_sd_publisher.h",
-    "dnssd/public/dns_sd_querier.h",
-    "dnssd/public/dns_sd_service.h",
-    "dnssd/public/dns_sd_txt_record.cc",
-    "dnssd/public/dns_sd_txt_record.h",
   ]
 
-  public_deps = [
-    ":common",
+  deps = [
     ":mdns",
-    "../util",
-  ]
-}
-
-source_set("public") {
-  sources = [
-    "public/dns_sd_service_factory.h",
-    "public/dns_sd_service_publisher.h",
-    "public/dns_sd_service_watcher.h",
-  ]
-
-  public_deps = [
-    ":common",
-    ":dnssd",
+    ":public",
+    "../third_party/abseil",
     "../util",
   ]
 }
@@ -133,8 +118,9 @@ source_set("testing") {
     sources += [ "mdns/testing/hash_test_util_abseil.h" ]
   }
 
-  public_deps = [
+  deps = [
     ":mdns",
+    ":public",
     "../third_party/abseil",
     "../third_party/googletest:gmock",
     "../third_party/googletest:gtest",
diff --git a/discovery/DEPS b/discovery/DEPS
index de7afcec..4d758dcd 100644
--- a/discovery/DEPS
+++ b/discovery/DEPS
@@ -4,6 +4,6 @@ include_rules = [
   # Intra-discovery dependencies must be explicit.
   '-discovery',
 
-  # All discovery code can use discovery/common
+  # All discovery code can use discovery/common.
   '+discovery/common',
 ]
diff --git a/discovery/dnssd/impl/DEPS b/discovery/dnssd/impl/DEPS
index 243d363d..57d73c16 100644
--- a/discovery/dnssd/impl/DEPS
+++ b/discovery/dnssd/impl/DEPS
@@ -2,5 +2,13 @@
 
 include_rules = [
   '+discovery/dnssd/public',
-  '+discovery/mdns',
+  '+discovery/mdns/public',
+
+  # TODO(https://issuetracker.google.com/issues/194234872):
+  # Move these to discovery/mdns/public
+  '+discovery/mdns/mdns_domain_confirmed_provider.h',
+  '+discovery/mdns/mdns_record_changed_callback.h',
+  '+discovery/mdns/mdns_records.h',
+  
+  '+discovery/mdns/testing/mdns_test_util.h',
 ]
diff --git a/discovery/dnssd/public/DEPS b/discovery/dnssd/public/DEPS
new file mode 100644
index 00000000..e8ae0cbe
--- /dev/null
+++ b/discovery/dnssd/public/DEPS
@@ -0,0 +1,6 @@
+# -*- Mode: Python; -*-
+
+include_rules = [
+  # Layering rule.
+  '-discovery/dnssd/impl',
+]
diff --git a/discovery/mdns/DEPS b/discovery/mdns/DEPS
index 309d03f4..c0348a87 100644
--- a/discovery/mdns/DEPS
+++ b/discovery/mdns/DEPS
@@ -2,4 +2,6 @@
 
 include_rules = [
   '+discovery/mdns/public',
+  # DNS-SD is layered on top of mDNS.
+  '-discovery/dnssd',
 ]
diff --git a/discovery/mdns/public/DEPS b/discovery/mdns/public/DEPS
new file mode 100644
index 00000000..5b65c0e4
--- /dev/null
+++ b/discovery/mdns/public/DEPS
@@ -0,0 +1,8 @@
+# -*- Mode: Python; -*-
+include_rules = [
+  # Layering rule.
+  '-discovery/mdns',
+  # Except ourselves.
+  '+discovery/mdns/public',
+]
+
diff --git a/osp/impl/BUILD.gn b/osp/impl/BUILD.gn
index 8b50164f..54404a61 100644
--- a/osp/impl/BUILD.gn
+++ b/osp/impl/BUILD.gn
@@ -32,7 +32,6 @@ source_set("impl") {
     "../public",
   ]
   deps = [
-    "../../discovery:common",
     "../../discovery:dnssd",
     "../../discovery:public",
     "../../platform",