Recreate Main.enso file if it is missing. (https://github.com/enso-org/ide/pull/705)

Original commit: 709c277ded

gui/src/rust/ide/src/view/project.rs

@@ -3,6 +3,7 @@
 
 use crate::prelude::*;
 
+use crate::controller::FilePath;
 use crate::model::module::Path as ModulePath;
 use crate::view::layout::ViewLayout;
 
@@ -42,6 +43,9 @@ pub const INITIAL_MODULE_NAME:&str = "Main";
 /// This is the definition whose graph will be opened on IDE start.
 pub const MAIN_DEFINITION_NAME:&str = "main";
 
+/// The default content of the newly created initial module file.
+pub const DEFAULT_MAIN_CONTENT:&str = r#"main = IO.println "Hello, World!""#;
+
 
 
 // ===================
@@ -76,13 +80,26 @@ pub fn initial_module_path(project:&model::Project) -> FallibleResult<ModulePath
     model::module::Path::from_name_segments(project.content_root_id(),&[INITIAL_MODULE_NAME])
 }
 
+/// Create a file with default content if it does not already exist.
+pub async fn recreate_if_missing(project:&model::Project, path:&FilePath, default_content:String)
+-> FallibleResult<()> {
+    let rpc = project.json_rpc();
+    if !rpc.file_exists(path).await?.exists {
+        rpc.write_file(path,&default_content).await?;
+    }
+    Ok(())
+}
+
 impl ProjectView {
     /// Create a new ProjectView.
     pub async fn new(logger:impl AnyLogger, model:model::Project)
     -> FallibleResult<Self> {
-        let logger            = Logger::sub(logger,"ProjectView");
+        let logger      = Logger::sub(logger,"ProjectView");
-        let module_path       = initial_module_path(&model)?;
+        let module_path = initial_module_path(&model)?;
-        let file_path         = module_path.file_path().clone();
+        let file_path   = module_path.file_path().clone();
+        // TODO [mwu] This solution to recreate missing main file should be considered provisional
+        //   until proper decision is made. See: https://github.com/enso-org/enso/issues/1050
+        recreate_if_missing(&model,&file_path,DEFAULT_MAIN_CONTENT.into()).await?;
         let text_controller   = controller::Text::new(&logger,&model,file_path).await?;
         let method            = module_path.method_pointer(MAIN_DEFINITION_NAME);
         let graph_controller  = controller::ExecutedGraph::new(&logger,model.clone_ref(),method);