fix: remove unused import and adjust null checks

Author: phodal

exts/devins-lang/src/main/kotlin/cc/unitmesh/devti/language/utils/ProjectFileUtil.kt

@@ -8,7 +8,6 @@ import com.intellij.openapi.vfs.VirtualFile
 import com.intellij.openapi.vfs.VirtualFileManager
 import com.intellij.psi.search.FilenameIndex
 import com.intellij.psi.search.ProjectScope
-import java.util.concurrent.TimeUnit
 
 fun Project.lookupFile(path: String): VirtualFile? {
     val projectPath = this.guessProjectDir()?.toNioPath()

exts/devins-lang/src/test/kotlin/cc/unitmesh/devti/language/compiler/DevInCompilerTest.kt

@@ -2,22 +2,25 @@ package cc.unitmesh.devti.language.compiler
 
 import cc.unitmesh.devti.language.psi.DevInFile
 import com.intellij.testFramework.fixtures.LightJavaCodeInsightFixtureTestCase
+import org.intellij.lang.annotations.Language
 import org.jetbrains.kotlin.konan.file.File
 
 class DevInCompilerTest : LightJavaCodeInsightFixtureTestCase() {
     fun testNormalString() {
-        val code = "Normal String /"
+        @Language("DevIn")
+        val code = "Normal String"
         val file = myFixture.configureByText("test.devin", code)
 
         val compile = DevInsCompiler(project, file as DevInFile, myFixture.editor).compile()
         assertEquals("Normal String /", compile.output)
     }
 
     fun testForWriting() {
-        // add fake code to project
         val projectPath = project.basePath + File.separator
-        myFixture.configureByText("Sample.devin", "Sample Text")
+
+        @Language("DevIn")
         val code = "/write:${projectPath}Sample.devin#L1-L2\n```devin\nNormal String /\n```"
+        myFixture.configureByText("Sample.devin", "Sample Text")
         val file = myFixture.configureByText("test.devin", code)
 
         try {
@@ -29,6 +32,7 @@ class DevInCompilerTest : LightJavaCodeInsightFixtureTestCase() {
     }
 
     fun testForRefactoring() {
+        @Language("DevIn")
         val code = "/refactor:rename cc.unitmesh.devti.language.run.DevInsProgramRunner to cc.unitmesh.devti.language.run.DevInsProgramRunnerImpl"
         val file = myFixture.configureByText("test.devin", code)