Move register variable to its own separate class

src/test/java/org/jetbrains/plugins/ideavim/ex/implementation/services/VimVariableServiceTest.kt

@@ -116,34 +116,4 @@ class VimVariableServiceTest : VimTestCase() {
     assertState("1\n2\n1\n2\n1\n2\n1\n2\n${c}1\n")
   }
 
-  @Test
-  fun `test v register`() {
-    configureByText("abcd")
-    // Check default register
-    typeText(commandToKeys("echo v:register"))
-    assertExOutput("\"")
-    // Check default register in expression
-    enterCommand(
-      """
-      nnoremap <expr> X ':echo v:register<CR>'
-      """.trimIndent(),
-    )
-    typeText("X")
-    assertExOutput("\"")
-    // Check named register
-    typeText("\"w")
-    typeText(commandToKeys("echo v:register"))
-    assertExOutput("w")
-    // Check named register in expression
-    // Here the key is that the register is defined as part of the expression
-    // itself, i.e. it hasn't been committed yet as the current register
-    enterCommand(
-      """
-      vnoremap <expr> y '"' . v:register . 'y'
-      """.trimIndent(),
-    )
-    typeText("vl\"zy")
-    val register = injector.registerGroup.getRegisters().filter { reg -> reg.name == 'z' }.first()
-    assertEquals("ab", register.text)
-  }
 }

src/test/java/org/jetbrains/plugins/ideavim/ex/implementation/variables/RegisterVariableTest.kt

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2003-2024 The IdeaVim authors
+ *
+ * Use of this source code is governed by an MIT-style
+ * license that can be found in the LICENSE.txt file or at
+ * https://opensource.org/licenses/MIT.
+ */
+
+package org.jetbrains.plugins.ideavim.ex.implementation.variables
+
+import com.maddyhome.idea.vim.api.injector
+import org.jetbrains.plugins.ideavim.VimTestCase
+import org.junit.jupiter.api.Test
+import kotlin.test.assertEquals
+
+class RegisterVariableTest : VimTestCase() {
+
+  @Test
+  fun `test default v register`() {
+    configureByText("abcd")
+    typeText(commandToKeys("echo v:register"))
+    assertExOutput("\"")
+  }
+
+  @Test
+  fun `test default v register in expression mapping`() {
+    configureByText("abcd")
+    enterCommand("""nnoremap <expr> X ':echo v:register<CR>'""")
+    typeText("X")
+    assertExOutput("\"")
+  }
+
+  @Test
+  fun `test named v register`() {
+    configureByText("abcd")
+    typeText("\"w")
+    typeText(commandToKeys("echo v:register"))
+    assertExOutput("w")
+  }
+
+  @Test
+  fun `test named v register in expression mapping`() {
+    configureByText("abcd")
+    enterCommand("""vnoremap <expr> y '"' . v:register . 'y'""")
+    typeText("vl\"zy")
+    val register = injector.registerGroup.getRegisters()
+      .filter { reg -> reg.name == 'z' }
+      .first()
+    assertEquals("ab", register.text)
+  }
+
+}

vim-engine/src/main/kotlin/com/maddyhome/idea/vim/vimscript/model/variables/RegisterVariable.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2003-2024 The IdeaVim authors
+ *
+ * Use of this source code is governed by an MIT-style
+ * license that can be found in the LICENSE.txt file or at
+ * https://opensource.org/licenses/MIT.
+ */
+
+package com.maddyhome.idea.vim.vimscript.model.variables
+
+import com.maddyhome.idea.vim.KeyHandler
+import com.maddyhome.idea.vim.api.ExecutionContext
+import com.maddyhome.idea.vim.api.VimEditor
+import com.maddyhome.idea.vim.api.injector
+import com.maddyhome.idea.vim.vimscript.model.VimLContext
+import com.maddyhome.idea.vim.vimscript.model.datatypes.VimDataType
+import com.maddyhome.idea.vim.vimscript.model.datatypes.VimString
+
+/**
+ * The name of the register in effect for the current normal mode
+ * command (regardless of whether that command actually used a
+ * register). Or for the currently executing normal mode mapping
+ * (use this in custom commands that take a register).
+ * If none is supplied it is the default register '"', unless
+ * 'clipboard' contains "unnamed" or "unnamedplus", then it is
+ * "*" or '+' ("unnamedplus" prevails).
+ */
+class RegisterVariable : Variable() {
+
+  override fun evaluate(
+    name: String,
+    editor: VimEditor,
+    context: ExecutionContext,
+    vimContext: VimLContext,
+  ): VimDataType {
+    val register = KeyHandler.getInstance().keyHandlerState.commandBuilder.registerSnapshot
+      ?: injector.registerGroup.currentRegister
+    return VimString(register.toString())
+  }
+
+}

vim-engine/src/main/kotlin/com/maddyhome/idea/vim/vimscript/model/variables/Variable.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2003-2024 The IdeaVim authors
+ *
+ * Use of this source code is governed by an MIT-style
+ * license that can be found in the LICENSE.txt file or at
+ * https://opensource.org/licenses/MIT.
+ */
+
+package com.maddyhome.idea.vim.vimscript.model.variables
+
+import com.maddyhome.idea.vim.api.ExecutionContext
+import com.maddyhome.idea.vim.api.VimEditor
+import com.maddyhome.idea.vim.vimscript.model.VimLContext
+import com.maddyhome.idea.vim.vimscript.model.datatypes.VimDataType
+
+/**
+ * Base class for Vim variables
+ */
+abstract class Variable {
+  abstract fun evaluate(name: String, editor: VimEditor, context: ExecutionContext, vimContext: VimLContext): VimDataType
+}

vim-engine/src/main/kotlin/com/maddyhome/idea/vim/vimscript/services/VimVariableServiceBase.kt

@@ -27,6 +27,7 @@ import com.maddyhome.idea.vim.vimscript.model.expressions.Scope
 import com.maddyhome.idea.vim.vimscript.model.expressions.Variable
 import com.maddyhome.idea.vim.vimscript.model.statements.FunctionDeclaration
 import com.maddyhome.idea.vim.vimscript.model.statements.FunctionFlag
+import com.maddyhome.idea.vim.vimscript.model.variables.RegisterVariable
 
 abstract class VimVariableServiceBase : VariableService {
   private var globalVariables: MutableMap<String, VimDataType> = mutableMapOf()
@@ -181,16 +182,7 @@ abstract class VimVariableServiceBase : VariableService {
       "count1" -> VimInt(KeyHandler.getInstance().keyHandlerState.commandBuilder.calculateCount0Snapshot().coerceAtLeast(1))
       "searchforward" -> VimInt(if (injector.searchGroup.getLastSearchDirection() == Direction.FORWARDS) 1 else 0)
       "register" -> {
-        // The name of the register in effect for the current normal mode
-        // command (regardless of whether that command actually used a
-        // register). Or for the currently executing normal mode mapping
-        // (use this in custom commands that take a register).
-        // If none is supplied it is the default register '"', unless
-        // 'clipboard' contains "unnamed" or "unnamedplus", then it is
-        // "*" or '+' ("unnamedplus" prevails).
-        val register = KeyHandler.getInstance().keyHandlerState.commandBuilder.registerSnapshot
-          ?: injector.registerGroup.currentRegister
-        VimString(register.toString())
+         RegisterVariable().evaluate(name, editor, context, vimContext)
       }
       else -> throw ExException("The 'v:${name}' variable is not implemented yet")
     }