fix(exts/devin-lang): enhance CodeBlockElement to correctly handle in…

…jection host validations #101

Previously, the `CodeBlockElement` class was using a hardcoded check to determine its ability to accept language injections, which was not ideal. This commit introduces a more robust method, `isAbleToAcceptInjections`, that takes into account the presence of start and end blocks, as well as the number of content elements within the code block. This ensures that the injection logic is more accurate and flexible, reducing the risk of incorrect language injections.

exts/devin-lang/src/main/kotlin/cc/unitmesh/language/parser/CodeBlockElement.kt

@@ -17,8 +17,15 @@ import com.intellij.psi.util.*
 class CodeBlockElement(node: ASTNode) : ASTWrapperPsiElement(node), PsiLanguageInjectionHost,
     InjectionBackgroundSuppressor {
     override fun isValidHost(): Boolean {
-        // use MarkdownCodeFenceUtils.isAbleToAcceptInjections
-        return true
+        return isAbleToAcceptInjections(this)
+    }
+
+    private fun isAbleToAcceptInjections(host: CodeBlockElement): Boolean {
+        val hasStartBlock = host.firstChild?.elementType != DevInTypes.CODE_BLOCK_START
+        val hasEndBlock = host.lastChild?.elementType != DevInTypes.CODE_BLOCK_END
+        val hasContents = host.children.count { it.hasType(DevInTypes.CODE_CONTENTS) } < 2
+
+        return !(hasStartBlock && hasEndBlock && hasContents)
     }
 
     override fun updateText(text: String): PsiLanguageInjectionHost {
@@ -33,10 +40,6 @@ class CodeBlockElement(node: ASTNode) : ASTWrapperPsiElement(node), PsiLanguageI
         return findChildByType(DevInTypes.LANGUAGE_ID)
     }
 
-    fun getContents(): PsiElement? {
-        return findChildByType(DevInTypes.CODE_CONTENTS)
-    }
-
     companion object {
         fun obtainFenceContent(element: CodeBlockElement): List<PsiElement>? {
             return CachedValuesManager.getCachedValue(element) {