feat: do not import BuildConfig/R, but use FQDN reference (#871)

* feat: replace {{ packageName }} in deps' packageImportPath

* chore: extract interpolating to a separate function

* feat: add support for templating in packageInstance too

* docs: add paragraphs about interpolation

* Update packages/platform-android/native_modules.gradle

* Fix GH whitespace changes

* Make the change backwards-compatible

Libraries already expect to be able to use R and BuildConfig
classes without having to worry about their packages. To match the
expectations the script will replace un-fully-qualified references
to fully-qualified.

* Update dependencies.md

* Update native_modules.gradle

* Update native_modules.gradle

Co-authored-by: Mike Grabowski <grabbou@gmail.com>

packages/platform-android/native_modules.gradle

@@ -125,11 +125,37 @@ class ReactNativeModules {
     String packageClassInstances = ""
 
     if (packages.size() > 0) {
-      packageImports = "import ${packageName}.BuildConfig;\nimport ${packageName}.R;\n\n"
-      packageImports = packageImports + packages.collect {
-        "// ${it.name}\n${it.packageImportPath}"
+      def interpolateDynamicValues = {
+        it
+                // Before adding the package replacement mechanism,
+                // BuildConfig and R classes were imported automatically
+                // into the scope of the file. We want to replace all
+                // non-FQDN references to those classes with the package name 
+                // of the MainApplication.
+                //
+                // We want to match "R" or "BuildConfig":
+                //  - new Package(R.string…),
+                //  - Module.configure(BuildConfig);
+                //    ^ hence including (BuildConfig|R)
+                // but we don't want to match "R":
+                //  - new Package(getResources…),
+                //  - new PackageR…,
+                //  - new Royal…,
+                //    ^ hence excluding \w before and after matches
+                // and "BuildConfig" that has FQDN reference:
+                //  - Module.configure(com.acme.BuildConfig);
+                //    ^ hence excluding . before the match.
+                .replaceAll(~/([^.\w])(BuildConfig|R)([^\w])/, {
+                  wholeString, prefix, className, suffix ->
+                    "${prefix}${packageName}.${className}${suffix}"
+                })
+      }
+      packageImports = packages.collect {
+        "// ${it.name}\n${interpolateDynamicValues(it.packageImportPath)}"
       }.join('\n')
-      packageClassInstances = ",\n      " + packages.collect { it.packageInstance }.join(",\n      ")
+      packageClassInstances = ",\n      " + packages.collect {
+        interpolateDynamicValues(it.packageInstance)
+      }.join(",\n      ")
     }
 
     String generatedFileContents = generatedFileContentsTemplate