gate indexstore highlighting engine behind the UNIDOC_ENABLE_INDEXSTORE=1 environment variable

Author: tayloraswift

Package.resolved

@@ -1,15 +1,6 @@
 {
-  "originHash" : "0c04c8df0571a4795562655875b6a18b9c74a5e3ac13781dbd39f81c6b122a5d",
+  "originHash" : "11a2c92dc12e2d1090f389f23c98adcb98ad3e0b6ccf1e724d65aeb0152c5554",
   "pins" : [
-    {
-      "identity" : "indexstore-db",
-      "kind" : "remoteSourceControl",
-      "location" : "https://github.com/apple/indexstore-db",
-      "state" : {
-        "branch" : "swift-5.10-RELEASE",
-        "revision" : "89ec16c2ac1bb271614e734a2ee792224809eb20"
-      }
-    },
     {
       "identity" : "swift-atomics",
       "kind" : "remoteSourceControl",

Package.swift

@@ -1,9 +1,10 @@
 // swift-tools-version:5.10
+import class Foundation.ProcessInfo
 import PackageDescription
 import CompilerPluginSupport
 
 let package:Package = .init(
-    name: "swift-unidoc",
+    name: "Swift Unidoc",
     platforms: [.macOS(.v14)],
     products: [
         .executable(name: "ssgc", targets: ["ssgc"]),
@@ -102,9 +103,6 @@ let package:Package = .init(
         .package(url: "https://github.com/tayloraswift/swift-png", .upToNextMinor(
             from: "4.4.2")),
 
-        .package(url: "https://github.com/apple/indexstore-db",
-            branch: "swift-5.10-RELEASE"),
-
         .package(url: "https://github.com/apple/swift-atomics", .upToNextMinor(
             from: "1.2.0")),
         .package(url: "https://github.com/apple/swift-collections.git", .upToNextMinor(
@@ -303,12 +301,6 @@ let package:Package = .init(
                 .product(name: "SwiftParser", package: "swift-syntax"),
             ]),
 
-        .target(name: "MarkdownPluginSwift_IndexStoreDB",
-            dependencies: [
-                .target(name: "MarkdownPluginSwift"),
-                .product(name: "IndexStoreDB", package: "indexstore-db"),
-            ]),
-
         .target(name: "MarkdownSemantics",
             dependencies: [
                 .target(name: "MarkdownAST"),
@@ -757,6 +749,25 @@ let package:Package = .init(
         .target(name: "guides", path: "Guides"),
     ])
 
+switch ProcessInfo.processInfo.environment["UNIDOC_ENABLE_INDEXSTORE"]?.lowercased()
+{
+case "1"?, "true"?:
+    package.dependencies.append(.package(url: "https://github.com/apple/indexstore-db",
+        branch: "swift-5.10-RELEASE"))
+
+    package.targets.append(.target(name: "MarkdownPluginSwift_IndexStoreDB",
+        dependencies: [
+            .target(name: "MarkdownPluginSwift"),
+            .product(name: "IndexStoreDB", package: "indexstore-db"),
+        ]))
+
+default:
+    package.targets.append(.target(name: "MarkdownPluginSwift_IndexStoreDB",
+        dependencies: [
+            .target(name: "MarkdownPluginSwift"),
+        ]))
+}
+
 for target:PackageDescription.Target in package.targets
 {
     if  target.name == "_AsyncChannel"