[Kotlin] Make sure namespace path exist for code generation (#7357)

With a change introduce in 385dda5c3785ed8d6a35868bc169f07e40e889087fd2edc66,
flatc was not able to emit code for Kotlin if a namespace is specified
and the folders do not exist. The fix create folders if neded.

Additional changes are introduced in gradle files to bring more visibility
to the error messages.

Co-authored-by: Derek Bailey <derekbailey@google.com>

.github/workflows/build.yml

@@ -168,8 +168,6 @@ jobs:
 
   build-android:
    name: Build Android (on Linux)
-   # Renable once it is working again.
-   if: false
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v2

android/app/build.gradle

@@ -33,7 +33,6 @@ android {
     }
   }
 
-  ndkVersion "21.3.6528147"
   externalNativeBuild {
     cmake {
       path "src/main/cpp/CMakeLists.txt"
@@ -52,16 +51,17 @@ android {
     fbsFiles.forEach{
       commandLineArgs.add(it.path)
     }
+
     commandLine commandLineArgs
 
     doFirst {
       delete "$outputCppDir/"
       mkdir "$outputCppDir/"
     }
+
     doLast {
-      if (execResult.getExitValue() != 0) {
-        println(standardOutput.toString())
-        throw new GradleException("flatc command line failed")
+      if (executionResult.get().exitValue != 0) {
+        throw new GradleException("flatc failed with: ${executionResult.get().toString()}")
       }
     }
   }
@@ -74,6 +74,10 @@ android {
 
     standardOutput = new ByteArrayOutputStream()
     errorOutput = new ByteArrayOutputStream()
+
+    setErrorOutput(errorOutput)
+    setStandardOutput(standardOutput)
+
     def commandLineArgs = ['flatc', '-o', outputKotlinDir, '--kotlin']
     fbsFiles.forEach{
       commandLineArgs.add(it.path)
@@ -85,17 +89,16 @@ android {
       mkdir "$outputKotlinDir/"
     }
     doLast {
-      if (execResult.getExitValue() != 0) {
-        println(standardOutput.toString())
-        throw new GradleException("flatc command line failed")
+      if (executionResult.get().exitValue != 0) {
+        throw new GradleException("flatc failed with: ${executionResult.get().toString()}")
       }
     }
   }
 
   afterEvaluate {
-    android.applicationVariants.all { variant ->
-      variant.javaCompiler.dependsOn(generateFbsKotlin)
-      variant.javaCompiler.dependsOn(generateFbsCpp)
+    tasks.named("preBuild") {
+      dependsOn(generateFbsKotlin)
+      dependsOn(generateFbsCpp)
     }
   }
 

android/app/src/main/cpp/generated/animal_generated.h

@@ -35,7 +35,7 @@ struct Animal FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
            verifier.VerifyString(name()) &&
            VerifyOffset(verifier, VT_SOUND) &&
            verifier.VerifyString(sound()) &&
-           VerifyField<uint16_t>(verifier, VT_WEIGHT) &&
+           VerifyField<uint16_t>(verifier, VT_WEIGHT, 2) &&
            verifier.EndTable();
   }
 };
@@ -57,7 +57,6 @@ struct AnimalBuilder {
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }
-  AnimalBuilder &operator=(const AnimalBuilder &);
   flatbuffers::Offset<Animal> Finish() {
     const auto end = fbb_.EndTable(start_);
     auto o = flatbuffers::Offset<Animal>(end);

android/app/src/main/java/generated/com/fbs/app/Animal.kt

@@ -7,7 +7,6 @@ import kotlin.math.sign
 import com.google.flatbuffers.*
 
 @Suppress("unused")
-@ExperimentalUnsignedTypes
 class Animal : Table() {
 
     fun __init(_i: Int, _bb: ByteBuffer)  {

android/gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.4.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.4.2-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

src/idl_gen_kotlin.cpp

@@ -134,9 +134,10 @@ class KotlinGenerator : public BaseGenerator {
       code += "import com.google.flatbuffers.*\n\n";
     }
     code += classcode;
-    auto filename = namer_.Directories(ns)
-                  + namer_.File(defname, SkipFile::Suffix);
-
+    const std::string dirs = namer_.Directories(ns);
+    EnsureDirExists(dirs);
+    const std::string filename =
+        dirs + namer_.File(defname, /*skips=*/SkipFile::Suffix);
     return SaveFile(filename.c_str(), code, false);
   }