Makes 'system-ghc' Stack option configurable

src/main/scala/intellij/haskell/external/execution/StackCommandLine.scala

@@ -29,6 +29,7 @@ import com.intellij.openapi.util.Key
 import com.intellij.openapi.vfs.{CharsetToolkit, VfsUtil}
 import intellij.haskell.HaskellNotificationGroup
 import intellij.haskell.sdk.HaskellSdkType
+import intellij.haskell.settings.HaskellSettingsState
 import intellij.haskell.stackyaml.StackYamlComponent
 import intellij.haskell.util.{HaskellFileUtil, HaskellProjectUtil}
 
@@ -60,7 +61,7 @@ object StackCommandLine {
 
   def installTool(project: Project, toolName: String): Boolean = {
     import intellij.haskell.GlobalInfo._
-    val systemGhcOption = if (StackYamlComponent.isNixEnabled(project)) {
+    val systemGhcOption = if (StackYamlComponent.isNixEnabled(project) || !HaskellSettingsState.useSystemGhc) {
       Seq()
     } else {
       Seq("--system-ghc")

src/main/scala/intellij/haskell/settings/HaskellConfigurable.scala

@@ -26,6 +26,7 @@ import javax.swing.event.DocumentEvent
 class HaskellConfigurable extends Configurable {
   private var isModifiedByUser = false
   private val hlintOptionsField = new JTextField
+  private val useSystemGhcToggle = new JCheckBox
   private val replTimeoutField = new JTextField
   private val replTimeoutLabel = new JLabel("Changed timeout will take effect after restarting project")
   private val newProjectTemplateNameField = new JTextField
@@ -92,6 +93,7 @@ class HaskellConfigurable extends Configurable {
     addLabeledControl(2, ReplTimeout, replTimeoutField)
     addLabeledControl(3, "", replTimeoutLabel)
     addLabeledControl(4, NewProjectTemplateName, newProjectTemplateNameField)
+    addLabeledControl(5, BuildToolsUsingSystemGhc, useSystemGhcToggle)
 
     settingsPanel.add(new JPanel(), baseGridBagConstraints.setConstraints(
       gridx = 0,
@@ -107,6 +109,7 @@ class HaskellConfigurable extends Configurable {
     val state = HaskellSettingsPersistentStateComponent.getInstance().getState
     state.replTimeout = validREPLTimeout
     state.hlintOptions = hlintOptionsField.getText
+    state.useSystemGhc = useSystemGhcToggle.isSelected
     state.newProjectTemplateName = newProjectTemplateNameField.getText
   }
 
@@ -130,6 +133,7 @@ class HaskellConfigurable extends Configurable {
   override def reset(): Unit = {
     val state = HaskellSettingsPersistentStateComponent.getInstance().getState
     hlintOptionsField.setText(state.hlintOptions)
+    useSystemGhcToggle.setSelected(state.useSystemGhc)
     replTimeoutField.setText(state.replTimeout.toString)
     newProjectTemplateNameField.setText(state.newProjectTemplateName)
   }
@@ -139,4 +143,5 @@ object HaskellConfigurable {
   final val ReplTimeout = "Background REPL timeout in seconds"
   final val HlintOptions = "Hlint options"
   final val NewProjectTemplateName = "Template name for new project"
-}
+  final val BuildToolsUsingSystemGhc = "Build tools using system GHC"
+}

src/main/scala/intellij/haskell/settings/HaskellSettingsPersistentStateComponent.java

@@ -50,6 +50,7 @@ public class HaskellSettingsPersistentStateComponent implements PersistentStateC
     static class HaskellSettingsState {
         public Integer replTimeout = 30;
         public String hlintOptions = "";
+        public Boolean useSystemGhc = true;
         public Boolean reformatCodeBeforeCommit = false;
         public Boolean optimizeImportsBeforeCommit = false;
         public String newProjectTemplateName = "new-template";

src/main/scala/intellij/haskell/settings/HaskellSettingsState.scala

@@ -27,6 +27,10 @@ object HaskellSettingsState {
     state.hlintOptions
   }
 
+  def useSystemGhc(): Boolean = {
+    state.useSystemGhc
+  }
+
   def getNewProjectTemplateName: String = {
     state.newProjectTemplateName
   }