test: add FileStore active document regression

Author: georgewfraser

src/test/java/org/javacs/FileStoreTest.java

@@ -3,14 +3,21 @@
 import static org.hamcrest.Matchers.*;
 import static org.hamcrest.MatcherAssert.assertThat;
 
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.Set;
 import org.junit.Before;
 import org.junit.Test;
+import org.javacs.lsp.DidOpenTextDocumentParams;
+import org.javacs.lsp.TextDocumentItem;
 
 public class FileStoreTest {
 
     @Before
     public void setWorkspaceRoot() {
+        FileStore.reset();
         FileStore.setWorkspaceRoots(Set.of(LanguageServerFixture.DEFAULT_WORKSPACE_ROOT));
     }
 
@@ -26,4 +33,30 @@ public void missingFile() {
         assertThat(FileStore.packageName(file), nullValue());
         assertThat(FileStore.modified(file), nullValue());
     }
+
+    @Test
+    public void inputReadersPreferActiveDocumentContents() throws IOException {
+        Path file = Files.createTempFile("FileStoreTest", ".java");
+        try {
+            Files.writeString(file, "class Foo { int onDisk; }\n");
+
+            var open = new DidOpenTextDocumentParams();
+            open.textDocument = new TextDocumentItem();
+            open.textDocument.uri = file.toUri();
+            open.textDocument.languageId = "java";
+            open.textDocument.version = 1;
+            open.textDocument.text = "class Foo { int inMemory; }\n";
+            FileStore.open(open);
+
+            var fromInputStream = new String(FileStore.inputStream(file).readAllBytes(), StandardCharsets.UTF_8);
+            var fromBufferedReader = FileStore.bufferedReader(file).readLine();
+
+            assertThat(fromInputStream, containsString("inMemory"));
+            assertThat(fromInputStream, not(containsString("onDisk")));
+            assertThat(fromBufferedReader, containsString("inMemory"));
+            assertThat(fromBufferedReader, not(containsString("onDisk")));
+        } finally {
+            Files.deleteIfExists(file);
+        }
+    }
 }