3 files changed, 64 insertions, 0 deletions

diff --git a/xtask/src/codegen.rs b/xtask/src/codegen.rs
index f5f4b964a..209caacc3 100644
--- a/xtask/src/codegen.rs
+++ b/xtask/src/codegen.rs
@@ -9,6 +9,7 @@ mod gen_syntax;
 mod gen_parser_tests;
 mod gen_assists_docs;
 mod gen_feature_docs;
+mod gen_unstable_future_descriptor;
 
 use std::{
     fmt, mem,
@@ -22,8 +23,12 @@ pub use self::{
     gen_feature_docs::generate_feature_docs,
     gen_parser_tests::generate_parser_tests,
     gen_syntax::generate_syntax,
+    gen_unstable_future_descriptor::generate_unstable_future_descriptor,
 };
 
+// Directory used by xtask 
+const STORAGE: &str = ".xtask";
+
 const GRAMMAR_DIR: &str = "crates/ra_parser/src/grammar";
 const OK_INLINE_TESTS_DIR: &str = "crates/ra_syntax/test_data/parser/inline/ok";
 const ERR_INLINE_TESTS_DIR: &str = "crates/ra_syntax/test_data/parser/inline/err";
@@ -35,6 +40,9 @@ const AST_TOKENS: &str = "crates/ra_syntax/src/ast/generated/tokens.rs";
 const ASSISTS_DIR: &str = "crates/ra_assists/src/handlers";
 const ASSISTS_TESTS: &str = "crates/ra_assists/src/tests/generated.rs";
 
+const REPOSITORY_URL: &str = "https://github.com/rust-lang/rust";
+const UNSTABLE_FEATURE: &str = "crates/ra_ide/src/completion/unstable_feature_descriptor.rs";
+
 #[derive(Debug, PartialEq, Eq, Clone, Copy)]
 pub enum Mode {
     Overwrite,
diff --git a/xtask/src/codegen/gen_unstable_future_descriptor.rs b/xtask/src/codegen/gen_unstable_future_descriptor.rs
new file mode 100644
index 000000000..298696fbb
--- /dev/null
+++ b/xtask/src/codegen/gen_unstable_future_descriptor.rs
@@ -0,0 +1,55 @@
+//! Generates descriptors structure for unstable feature from Unstable Book
+
+use crate::{
+    codegen::{self, project_root, Mode, Result},
+};
+use std::process::Command;
+use std::fs;
+use std::path::{Path, PathBuf};
+use walkdir::{DirEntry, WalkDir};
+use quote::{format_ident, quote};
+use crate::codegen::update;
+
+pub fn generate_unstable_future_descriptor(mode: Mode) -> Result<()> {
+    let path = project_root().join(codegen::STORAGE);
+    fs::create_dir_all(path.clone())?;
+
+    Command::new("git").current_dir(path.clone()).arg("init").output()?;
+    Command::new("git").current_dir(path.clone()).args(&["remote", "add", "-f", "origin", codegen::REPOSITORY_URL]).output()?;
+    Command::new("git").current_dir(path.clone()).args(&["sparse-checkout", "set", "/src/doc/unstable-book/src/"]).output()?;
+    Command::new("git").current_dir(path.clone()).args(&["pull", "origin", "master"]).output()?;
+    //TODO: check git, and do pull 
+
+    let src_dir = path.join("src/doc/unstable-book/src");
+    let files = WalkDir::new(src_dir.join("language-features"))
+        .into_iter()
+        .chain(WalkDir::new(src_dir.join("library-features")))
+        .filter_map(|e| e.ok())
+        .filter(|entry| {
+            // Get all `.md ` files
+            entry.file_type().is_file() && entry.path().extension().map(|ext| ext == "md").unwrap_or(false)
+        })
+        .collect::<Vec<_>>();
+
+    let definitions = files.iter().map(|entry| {
+        let path = entry.path();
+        let feature_ident = format!("{}", path.file_stem().unwrap().to_str().unwrap().replace("-", "_"));
+        let doc = format!("{}", std::fs::read_to_string(path).unwrap() );
+       
+        quote!{ LintCompletion { label: #feature_ident, description: #doc } }
+    }).collect::<Vec<_>>();
+    
+    let ts = quote! {
+        use crate::completion::LintCompletion;
+
+        pub const UNSTABLE_FEATURE_DESCRIPTOR:  &[LintCompletion] = &[
+            #(#definitions),*
+        ];
+    };
+    
+    let destination = project_root().join(codegen::UNSTABLE_FEATURE);
+    let contents = crate::reformat(ts.to_string())?;
+    update(destination.as_path(), &contents, mode)?;
+
+    Ok(())
+}
\ No newline at end of file
diff --git a/xtask/src/main.rs b/xtask/src/main.rs
index b69b884e5..71caff248 100644
--- a/xtask/src/main.rs
+++ b/xtask/src/main.rs
@@ -76,6 +76,7 @@ FLAGS:
         "codegen" => {
             args.finish()?;
             codegen::generate_syntax(Mode::Overwrite)?;
+            codegen::generate_unstable_future_descriptor(Mode::Overwrite)?;
             codegen::generate_parser_tests(Mode::Overwrite)?;
             codegen::generate_assists_tests(Mode::Overwrite)?;
             codegen::generate_assists_docs(Mode::Overwrite)?;