Fix #848: nest codeBlock problem for issue

src/main/java/com/squareup/javapoet/CodeBlock.java

@@ -18,6 +18,7 @@
 import java.io.IOException;
 import java.lang.reflect.Type;
 import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.regex.Matcher;
@@ -126,6 +127,26 @@ public static CodeBlock join(Iterable<CodeBlock> codeBlocks, String separator) {
         CodeBlockJoiner::merge,
         CodeBlockJoiner::join);
   }
+  /**
+   * Joins {@code codeBlocks} into a single {@link CodeBlock}, each separated by {@code separators}.
+   * For example, joining {@code String s}, {@code Object o} and {@code int i} using {@code "[, ,\] "}
+   * would produce {@code String s, Object o\ int i}.
+   */
+  public static CodeBlock join(Iterable<CodeBlock> codeBlocks, String[] separators) {
+    List<CodeBlock> list = new ArrayList<>();
+    Iterator<CodeBlock> iter = codeBlocks.iterator();
+    list.add((CodeBlock) iter.next());
+
+    for (String separator : separators) {
+      list.add((CodeBlock) iter.next());
+      list.add(join(list, separator));
+      list.remove(0);
+      list.remove(0);
+    }
+    return list.get(0);
+  }
+
+
 
   /**
    * A {@link Collector} implementation that joins {@link CodeBlock} instances together into one

src/main/java/com/squareup/javapoet/CodeWriter.java

@@ -362,6 +362,11 @@ private void emitLiteral(Object o) throws IOException {
       annotationSpec.emit(this, true);
     } else if (o instanceof CodeBlock) {
       CodeBlock codeBlock = (CodeBlock) o;
+      CodeBlock.Builder builder = CodeBlock.builder();
+      builder.formatParts.addAll(codeBlock.formatParts);
+      builder.args.addAll(codeBlock.args);
+      builder.formatParts.remove("$[");
+      builder.formatParts.remove("$]");
       emit(codeBlock);
     } else {
       emitAndIndent(String.valueOf(o));

src/test/java/com/squareup/javapoet/CodeBlockTest.java

@@ -340,6 +340,36 @@ public final class CodeBlockTest {
     assertThat(joined.toString()).isEqualTo("start {\"hello\" || world.World || need tacos} end");
   }
 
+  @Test public void NestCodeBlock(){
+    CodeBlock inner = CodeBlock.builder()
+            .beginControlFlow("() ->")
+            .addStatement("return 42")
+            .endControlFlow()
+            .build();
+
+    CodeBlock outer =
+            CodeBlock.builder()
+                    .add(
+                            "$T lambda = $L;",
+                            ParameterizedTypeName.get(
+                                    ClassName.get(ArrayList.class), ClassName.get(Integer.class)),
+                            inner)
+                    .build();
+    assertThat(outer.toString()).isEqualTo("java.util.ArrayList<java.lang.Integer> lambda = () -> {\n" +
+            "  return 42;\n" +
+            "}\n" +
+            ";");
+
+  }
+  @Test public void joiningWithDifferentSeparator() {
+    List<CodeBlock> codeBlocks = new ArrayList<>();
+    codeBlocks.add(CodeBlock.of("$S", "hello"));
+    codeBlocks.add(CodeBlock.of("$T", ClassName.get("world", "World")));
+    codeBlocks.add(CodeBlock.of("need tacos"));
+    CodeBlock info = CodeBlock.join(codeBlocks, new String[]{" || "," | "});
+
+    assertThat(info.toString()).isEqualTo("\"hello\" || world.World | need tacos");
+  }
   @Test public void clear() {
     CodeBlock block = CodeBlock.builder()
         .addStatement("$S", "Test string")