5 files changed, 976 insertions, 0 deletions

diff --git a/xtask/src/bin/pre-commit.rs b/xtask/src/bin/pre-commit.rs
new file mode 100644
index 000000000..4ee864756
--- /dev/null
+++ b/xtask/src/bin/pre-commit.rs
@@ -0,0 +1,31 @@
+//! FIXME: write short doc here
+
+use std::process::Command;
+
+use xtask::{project_root, run, run_rustfmt, Overwrite, Result};
+
+fn main() -> Result<()> {
+    run_rustfmt(Overwrite)?;
+    update_staged()
+}
+
+fn update_staged() -> Result<()> {
+    let root = project_root();
+    let output = Command::new("git")
+        .arg("diff")
+        .arg("--diff-filter=MAR")
+        .arg("--name-only")
+        .arg("--cached")
+        .current_dir(&root)
+        .output()?;
+    if !output.status.success() {
+        Err(format!(
+            "`git diff --diff-filter=MAR --name-only --cached` exited with {}",
+            output.status
+        ))?;
+    }
+    for line in String::from_utf8(output.stdout)?.lines() {
+        run(&format!("git update-index --add {}", root.join(line).to_string_lossy()), ".")?;
+    }
+    Ok(())
+}
diff --git a/xtask/src/boilerplate_gen.rs b/xtask/src/boilerplate_gen.rs
new file mode 100644
index 000000000..39f1cae66
--- /dev/null
+++ b/xtask/src/boilerplate_gen.rs
@@ -0,0 +1,348 @@
+//! FIXME: write short doc here
+
+use std::{
+    collections::BTreeMap,
+    fs,
+    io::Write,
+    process::{Command, Stdio},
+};
+
+use proc_macro2::{Punct, Spacing};
+use quote::{format_ident, quote};
+use ron;
+use serde::Deserialize;
+
+use crate::{project_root, update, Mode, Result, AST, GRAMMAR, SYNTAX_KINDS};
+
+pub fn generate_boilerplate(mode: Mode) -> Result<()> {
+    let grammar = project_root().join(GRAMMAR);
+    let grammar: Grammar = {
+        let text = fs::read_to_string(grammar)?;
+        ron::de::from_str(&text)?
+    };
+
+    let syntax_kinds_file = project_root().join(SYNTAX_KINDS);
+    let syntax_kinds = generate_syntax_kinds(&grammar)?;
+    update(syntax_kinds_file.as_path(), &syntax_kinds, mode)?;
+
+    let ast_file = project_root().join(AST);
+    let ast = generate_ast(&grammar)?;
+    update(ast_file.as_path(), &ast, mode)?;
+
+    Ok(())
+}
+
+fn generate_ast(grammar: &Grammar) -> Result<String> {
+    let nodes = grammar.ast.iter().map(|(name, ast_node)| {
+        let variants =
+            ast_node.variants.iter().map(|var| format_ident!("{}", var)).collect::<Vec<_>>();
+        let name = format_ident!("{}", name);
+
+        let adt = if variants.is_empty() {
+            let kind = format_ident!("{}", to_upper_snake_case(&name.to_string()));
+            quote! {
+                #[derive(Debug, Clone, PartialEq, Eq, Hash)]
+                pub struct #name {
+                    pub(crate) syntax: SyntaxNode,
+                }
+
+                impl AstNode for #name {
+                    fn can_cast(kind: SyntaxKind) -> bool {
+                        match kind {
+                            #kind => true,
+                            _ => false,
+                        }
+                    }
+                    fn cast(syntax: SyntaxNode) -> Option<Self> {
+                        if Self::can_cast(syntax.kind()) { Some(Self { syntax }) } else { None }
+                    }
+                    fn syntax(&self) -> &SyntaxNode { &self.syntax }
+                }
+            }
+        } else {
+            let kinds = variants
+                .iter()
+                .map(|name| format_ident!("{}", to_upper_snake_case(&name.to_string())))
+                .collect::<Vec<_>>();
+
+            quote! {
+                #[derive(Debug, Clone, PartialEq, Eq, Hash)]
+                pub enum #name {
+                    #(#variants(#variants),)*
+                }
+
+                #(
+                impl From<#variants> for #name {
+                    fn from(node: #variants) -> #name {
+                        #name::#variants(node)
+                    }
+                }
+                )*
+
+                impl AstNode for #name {
+                    fn can_cast(kind: SyntaxKind) -> bool {
+                        match kind {
+                            #(#kinds)|* => true,
+                            _ => false,
+                        }
+                    }
+                    fn cast(syntax: SyntaxNode) -> Option<Self> {
+                        let res = match syntax.kind() {
+                            #(
+                            #kinds => #name::#variants(#variants { syntax }),
+                            )*
+                            _ => return None,
+                        };
+                        Some(res)
+                    }
+                    fn syntax(&self) -> &SyntaxNode {
+                        match self {
+                            #(
+                            #name::#variants(it) => &it.syntax,
+                            )*
+                        }
+                    }
+                }
+            }
+        };
+
+        let traits = ast_node.traits.iter().map(|trait_name| {
+            let trait_name = format_ident!("{}", trait_name);
+            quote!(impl ast::#trait_name for #name {})
+        });
+
+        let collections = ast_node.collections.iter().map(|(name, kind)| {
+            let method_name = format_ident!("{}", name);
+            let kind = format_ident!("{}", kind);
+            quote! {
+                pub fn #method_name(&self) -> AstChildren<#kind> {
+                    AstChildren::new(&self.syntax)
+                }
+            }
+        });
+
+        let options = ast_node.options.iter().map(|attr| {
+            let method_name = match attr {
+                Attr::Type(t) => format_ident!("{}", to_lower_snake_case(&t)),
+                Attr::NameType(n, _) => format_ident!("{}", n),
+            };
+            let ty = match attr {
+                Attr::Type(t) | Attr::NameType(_, t) => format_ident!("{}", t),
+            };
+            quote! {
+                pub fn #method_name(&self) -> Option<#ty> {
+                    AstChildren::new(&self.syntax).next()
+                }
+            }
+        });
+
+        quote! {
+            #adt
+
+            #(#traits)*
+
+            impl #name {
+                #(#collections)*
+                #(#options)*
+            }
+        }
+    });
+
+    let ast = quote! {
+        use crate::{
+            SyntaxNode, SyntaxKind::{self, *},
+            ast::{self, AstNode, AstChildren},
+        };
+
+        #(#nodes)*
+    };
+
+    let pretty = reformat(ast)?;
+    Ok(pretty)
+}
+
+fn generate_syntax_kinds(grammar: &Grammar) -> Result<String> {
+    let (single_byte_tokens_values, single_byte_tokens): (Vec<_>, Vec<_>) = grammar
+        .punct
+        .iter()
+        .filter(|(token, _name)| token.len() == 1)
+        .map(|(token, name)| (token.chars().next().unwrap(), format_ident!("{}", name)))
+        .unzip();
+
+    let punctuation_values = grammar.punct.iter().map(|(token, _name)| {
+        if "{}[]()".contains(token) {
+            let c = token.chars().next().unwrap();
+            quote! { #c }
+        } else {
+            let cs = token.chars().map(|c| Punct::new(c, Spacing::Joint));
+            quote! { #(#cs)* }
+        }
+    });
+    let punctuation =
+        grammar.punct.iter().map(|(_token, name)| format_ident!("{}", name)).collect::<Vec<_>>();
+
+    let full_keywords_values = &grammar.keywords;
+    let full_keywords =
+        full_keywords_values.iter().map(|kw| format_ident!("{}_KW", to_upper_snake_case(&kw)));
+
+    let all_keywords_values =
+        grammar.keywords.iter().chain(grammar.contextual_keywords.iter()).collect::<Vec<_>>();
+    let all_keywords_idents = all_keywords_values.iter().map(|kw| format_ident!("{}", kw));
+    let all_keywords = all_keywords_values
+        .iter()
+        .map(|name| format_ident!("{}_KW", to_upper_snake_case(&name)))
+        .collect::<Vec<_>>();
+
+    let literals =
+        grammar.literals.iter().map(|name| format_ident!("{}", name)).collect::<Vec<_>>();
+
+    let tokens = grammar.tokens.iter().map(|name| format_ident!("{}", name)).collect::<Vec<_>>();
+
+    let nodes = grammar.nodes.iter().map(|name| format_ident!("{}", name)).collect::<Vec<_>>();
+
+    let ast = quote! {
+        #![allow(bad_style, missing_docs, unreachable_pub)]
+        /// The kind of syntax node, e.g. `IDENT`, `USE_KW`, or `STRUCT_DEF`.
+        #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+        #[repr(u16)]
+        pub enum SyntaxKind {
+            // Technical SyntaxKinds: they appear temporally during parsing,
+            // but never end up in the final tree
+            #[doc(hidden)]
+            TOMBSTONE,
+            #[doc(hidden)]
+            EOF,
+            #(#punctuation,)*
+            #(#all_keywords,)*
+            #(#literals,)*
+            #(#tokens,)*
+            #(#nodes,)*
+
+            // Technical kind so that we can cast from u16 safely
+            #[doc(hidden)]
+            __LAST,
+        }
+        use self::SyntaxKind::*;
+
+        impl SyntaxKind {
+            pub fn is_keyword(self) -> bool {
+                match self {
+                    #(#all_keywords)|* => true,
+                    _ => false,
+                }
+            }
+
+            pub fn is_punct(self) -> bool {
+                match self {
+                    #(#punctuation)|* => true,
+                    _ => false,
+                }
+            }
+
+            pub fn is_literal(self) -> bool {
+                match self {
+                    #(#literals)|* => true,
+                    _ => false,
+                }
+            }
+
+            pub fn from_keyword(ident: &str) -> Option<SyntaxKind> {
+                let kw = match ident {
+                    #(#full_keywords_values => #full_keywords,)*
+                    _ => return None,
+                };
+                Some(kw)
+            }
+
+            pub fn from_char(c: char) -> Option<SyntaxKind> {
+                let tok = match c {
+                    #(#single_byte_tokens_values => #single_byte_tokens,)*
+                    _ => return None,
+                };
+                Some(tok)
+            }
+        }
+
+        #[macro_export]
+        macro_rules! T {
+            #((#punctuation_values) => { $crate::SyntaxKind::#punctuation };)*
+            #((#all_keywords_idents) => { $crate::SyntaxKind::#all_keywords };)*
+        }
+    };
+
+    reformat(ast)
+}
+
+fn reformat(text: impl std::fmt::Display) -> Result<String> {
+    let mut rustfmt = Command::new("rustfmt")
+        .arg("--config-path")
+        .arg(project_root().join("rustfmt.toml"))
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .spawn()?;
+    write!(rustfmt.stdin.take().unwrap(), "{}", text)?;
+    let output = rustfmt.wait_with_output()?;
+    let stdout = String::from_utf8(output.stdout)?;
+    let preamble = "Generated file, do not edit by hand, see `crate/ra_tools/src/codegen`";
+    Ok(format!("//! {}\n\n{}", preamble, stdout))
+}
+
+#[derive(Deserialize, Debug)]
+struct Grammar {
+    punct: Vec<(String, String)>,
+    keywords: Vec<String>,
+    contextual_keywords: Vec<String>,
+    literals: Vec<String>,
+    tokens: Vec<String>,
+    nodes: Vec<String>,
+    ast: BTreeMap<String, AstNode>,
+}
+
+#[derive(Deserialize, Debug)]
+struct AstNode {
+    #[serde(default)]
+    #[serde(rename = "enum")]
+    variants: Vec<String>,
+
+    #[serde(default)]
+    traits: Vec<String>,
+    #[serde(default)]
+    collections: Vec<(String, String)>,
+    #[serde(default)]
+    options: Vec<Attr>,
+}
+
+#[derive(Deserialize, Debug)]
+#[serde(untagged)]
+enum Attr {
+    Type(String),
+    NameType(String, String),
+}
+
+fn to_upper_snake_case(s: &str) -> String {
+    let mut buf = String::with_capacity(s.len());
+    let mut prev_is_upper = None;
+    for c in s.chars() {
+        if c.is_ascii_uppercase() && prev_is_upper == Some(false) {
+            buf.push('_')
+        }
+        prev_is_upper = Some(c.is_ascii_uppercase());
+
+        buf.push(c.to_ascii_uppercase());
+    }
+    buf
+}
+
+fn to_lower_snake_case(s: &str) -> String {
+    let mut buf = String::with_capacity(s.len());
+    let mut prev_is_upper = None;
+    for c in s.chars() {
+        if c.is_ascii_uppercase() && prev_is_upper == Some(false) {
+            buf.push('_')
+        }
+        prev_is_upper = Some(c.is_ascii_uppercase());
+
+        buf.push(c.to_ascii_lowercase());
+    }
+    buf
+}
diff --git a/xtask/src/help.rs b/xtask/src/help.rs
new file mode 100644
index 000000000..4c6bf6b53
--- /dev/null
+++ b/xtask/src/help.rs
@@ -0,0 +1,47 @@
+//! FIXME: write short doc here
+
+pub const GLOBAL_HELP: &str = "tasks
+
+USAGE:
+    ra_tools <SUBCOMMAND>
+
+FLAGS:
+    -h, --help       Prints help information
+
+SUBCOMMANDS:
+    format
+    format-hook
+    fuzz-tests
+    codegen
+    gen-tests
+    install
+    lint";
+
+pub const INSTALL_HELP: &str = "ra_tools-install
+
+USAGE:
+    ra_tools.exe install [FLAGS]
+
+FLAGS:
+        --client-code
+    -h, --help           Prints help information
+        --jemalloc
+        --server";
+
+pub fn print_no_param_subcommand_help(subcommand: &str) {
+    eprintln!(
+        "ra_tools-{}
+
+USAGE:
+    ra_tools {}
+
+FLAGS:
+    -h, --help       Prints help information",
+        subcommand, subcommand
+    );
+}
+
+pub const INSTALL_RA_CONFLICT: &str =
+    "error: The argument `--server` cannot be used with `--client-code`
+
+For more information try --help";
diff --git a/xtask/src/lib.rs b/xtask/src/lib.rs
new file mode 100644
index 000000000..a8685f567
--- /dev/null
+++ b/xtask/src/lib.rs
@@ -0,0 +1,332 @@
+//! FIXME: write short doc here
+
+mod boilerplate_gen;
+
+use std::{
+    collections::HashMap,
+    error::Error,
+    fs,
+    io::{Error as IoError, ErrorKind},
+    path::{Path, PathBuf},
+    process::{Command, Output, Stdio},
+};
+
+use itertools::Itertools;
+
+pub use self::boilerplate_gen::generate_boilerplate;
+
+pub type Result<T> = std::result::Result<T, Box<dyn Error>>;
+
+pub const GRAMMAR: &str = "crates/ra_syntax/src/grammar.ron";
+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";
+
+pub const SYNTAX_KINDS: &str = "crates/ra_parser/src/syntax_kind/generated.rs";
+pub const AST: &str = "crates/ra_syntax/src/ast/generated.rs";
+const TOOLCHAIN: &str = "stable";
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+pub enum Mode {
+    Overwrite,
+    Verify,
+}
+pub use Mode::*;
+
+#[derive(Debug)]
+pub struct Test {
+    pub name: String,
+    pub text: String,
+    pub ok: bool,
+}
+
+pub fn collect_tests(s: &str) -> Vec<(usize, Test)> {
+    let mut res = vec![];
+    let prefix = "// ";
+    let comment_blocks = s
+        .lines()
+        .map(str::trim_start)
+        .enumerate()
+        .group_by(|(_idx, line)| line.starts_with(prefix));
+
+    'outer: for (is_comment, block) in comment_blocks.into_iter() {
+        if !is_comment {
+            continue;
+        }
+        let mut block = block.map(|(idx, line)| (idx, &line[prefix.len()..]));
+
+        let mut ok = true;
+        let (start_line, name) = loop {
+            match block.next() {
+                Some((idx, line)) if line.starts_with("test ") => {
+                    break (idx, line["test ".len()..].to_string());
+                }
+                Some((idx, line)) if line.starts_with("test_err ") => {
+                    ok = false;
+                    break (idx, line["test_err ".len()..].to_string());
+                }
+                Some(_) => (),
+                None => continue 'outer,
+            }
+        };
+        let text: String =
+            itertools::join(block.map(|(_, line)| line).chain(::std::iter::once("")), "\n");
+        assert!(!text.trim().is_empty() && text.ends_with('\n'));
+        res.push((start_line, Test { name, text, ok }))
+    }
+    res
+}
+
+pub fn project_root() -> PathBuf {
+    Path::new(&env!("CARGO_MANIFEST_DIR")).ancestors().nth(1).unwrap().to_path_buf()
+}
+
+pub struct Cmd<'a> {
+    pub unix: &'a str,
+    pub windows: &'a str,
+    pub work_dir: &'a str,
+}
+
+impl Cmd<'_> {
+    pub fn run(self) -> Result<()> {
+        if cfg!(windows) {
+            run(self.windows, self.work_dir)
+        } else {
+            run(self.unix, self.work_dir)
+        }
+    }
+    pub fn run_with_output(self) -> Result<Output> {
+        if cfg!(windows) {
+            run_with_output(self.windows, self.work_dir)
+        } else {
+            run_with_output(self.unix, self.work_dir)
+        }
+    }
+}
+
+pub fn run(cmdline: &str, dir: &str) -> Result<()> {
+    do_run(cmdline, dir, |c| {
+        c.stdout(Stdio::inherit());
+    })
+    .map(|_| ())
+}
+
+pub fn run_with_output(cmdline: &str, dir: &str) -> Result<Output> {
+    do_run(cmdline, dir, |_| {})
+}
+
+pub fn run_rustfmt(mode: Mode) -> Result<()> {
+    match Command::new("rustup")
+        .args(&["run", TOOLCHAIN, "--", "cargo", "fmt", "--version"])
+        .stderr(Stdio::null())
+        .stdout(Stdio::null())
+        .status()
+    {
+        Ok(status) if status.success() => (),
+        _ => install_rustfmt()?,
+    };
+
+    if mode == Verify {
+        run(&format!("rustup run {} -- cargo fmt -- --check", TOOLCHAIN), ".")?;
+    } else {
+        run(&format!("rustup run {} -- cargo fmt", TOOLCHAIN), ".")?;
+    }
+    Ok(())
+}
+
+pub fn install_rustfmt() -> Result<()> {
+    run(&format!("rustup install {}", TOOLCHAIN), ".")?;
+    run(&format!("rustup component add rustfmt --toolchain {}", TOOLCHAIN), ".")
+}
+
+pub fn install_format_hook() -> Result<()> {
+    let result_path = Path::new(if cfg!(windows) {
+        "./.git/hooks/pre-commit.exe"
+    } else {
+        "./.git/hooks/pre-commit"
+    });
+    if !result_path.exists() {
+        run("cargo build --package xtask --bin pre-commit", ".")?;
+        if cfg!(windows) {
+            fs::copy("./target/debug/pre-commit.exe", result_path)?;
+        } else {
+            fs::copy("./target/debug/pre-commit", result_path)?;
+        }
+    } else {
+        Err(IoError::new(ErrorKind::AlreadyExists, "Git hook already created"))?;
+    }
+    Ok(())
+}
+
+pub fn run_clippy() -> Result<()> {
+    match Command::new("rustup")
+        .args(&["run", TOOLCHAIN, "--", "cargo", "clippy", "--version"])
+        .stderr(Stdio::null())
+        .stdout(Stdio::null())
+        .status()
+    {
+        Ok(status) if status.success() => (),
+        _ => install_clippy()?,
+    };
+
+    let allowed_lints = [
+        "clippy::collapsible_if",
+        "clippy::map_clone", // FIXME: remove when Iterator::copied stabilizes (1.36.0)
+        "clippy::needless_pass_by_value",
+        "clippy::nonminimal_bool",
+        "clippy::redundant_pattern_matching",
+    ];
+    run(
+        &format!(
+            "rustup run {} -- cargo clippy --all-features --all-targets -- -A {}",
+            TOOLCHAIN,
+            allowed_lints.join(" -A ")
+        ),
+        ".",
+    )?;
+    Ok(())
+}
+
+pub fn install_clippy() -> Result<()> {
+    run(&format!("rustup install {}", TOOLCHAIN), ".")?;
+    run(&format!("rustup component add clippy --toolchain {}", TOOLCHAIN), ".")
+}
+
+pub fn run_fuzzer() -> Result<()> {
+    match Command::new("cargo")
+        .args(&["fuzz", "--help"])
+        .stderr(Stdio::null())
+        .stdout(Stdio::null())
+        .status()
+    {
+        Ok(status) if status.success() => (),
+        _ => run("cargo install cargo-fuzz", ".")?,
+    };
+
+    run("rustup run nightly -- cargo fuzz run parser", "./crates/ra_syntax")
+}
+
+pub fn gen_tests(mode: Mode) -> Result<()> {
+    let tests = tests_from_dir(&project_root().join(Path::new(GRAMMAR_DIR)))?;
+    fn install_tests(tests: &HashMap<String, Test>, into: &str, mode: Mode) -> Result<()> {
+        let tests_dir = project_root().join(into);
+        if !tests_dir.is_dir() {
+            fs::create_dir_all(&tests_dir)?;
+        }
+        // ok is never actually read, but it needs to be specified to create a Test in existing_tests
+        let existing = existing_tests(&tests_dir, true)?;
+        for t in existing.keys().filter(|&t| !tests.contains_key(t)) {
+            panic!("Test is deleted: {}", t);
+        }
+
+        let mut new_idx = existing.len() + 1;
+        for (name, test) in tests {
+            let path = match existing.get(name) {
+                Some((path, _test)) => path.clone(),
+                None => {
+                    let file_name = format!("{:04}_{}.rs", new_idx, name);
+                    new_idx += 1;
+                    tests_dir.join(file_name)
+                }
+            };
+            update(&path, &test.text, mode)?;
+        }
+        Ok(())
+    }
+    install_tests(&tests.ok, OK_INLINE_TESTS_DIR, mode)?;
+    install_tests(&tests.err, ERR_INLINE_TESTS_DIR, mode)
+}
+
+fn do_run<F>(cmdline: &str, dir: &str, mut f: F) -> Result<Output>
+where
+    F: FnMut(&mut Command),
+{
+    eprintln!("\nwill run: {}", cmdline);
+    let proj_dir = project_root().join(dir);
+    let mut args = cmdline.split_whitespace();
+    let exec = args.next().unwrap();
+    let mut cmd = Command::new(exec);
+    f(cmd.args(args).current_dir(proj_dir).stderr(Stdio::inherit()));
+    let output = cmd.output()?;
+    if !output.status.success() {
+        Err(format!("`{}` exited with {}", cmdline, output.status))?;
+    }
+    Ok(output)
+}
+
+#[derive(Default, Debug)]
+struct Tests {
+    pub ok: HashMap<String, Test>,
+    pub err: HashMap<String, Test>,
+}
+
+fn tests_from_dir(dir: &Path) -> Result<Tests> {
+    let mut res = Tests::default();
+    for entry in ::walkdir::WalkDir::new(dir) {
+        let entry = entry.unwrap();
+        if !entry.file_type().is_file() {
+            continue;
+        }
+        if entry.path().extension().unwrap_or_default() != "rs" {
+            continue;
+        }
+        process_file(&mut res, entry.path())?;
+    }
+    let grammar_rs = dir.parent().unwrap().join("grammar.rs");
+    process_file(&mut res, &grammar_rs)?;
+    return Ok(res);
+    fn process_file(res: &mut Tests, path: &Path) -> Result<()> {
+        let text = fs::read_to_string(path)?;
+
+        for (_, test) in collect_tests(&text) {
+            if test.ok {
+                if let Some(old_test) = res.ok.insert(test.name.clone(), test) {
+                    Err(format!("Duplicate test: {}", old_test.name))?
+                }
+            } else {
+                if let Some(old_test) = res.err.insert(test.name.clone(), test) {
+                    Err(format!("Duplicate test: {}", old_test.name))?
+                }
+            }
+        }
+        Ok(())
+    }
+}
+
+fn existing_tests(dir: &Path, ok: bool) -> Result<HashMap<String, (PathBuf, Test)>> {
+    let mut res = HashMap::new();
+    for file in fs::read_dir(dir)? {
+        let file = file?;
+        let path = file.path();
+        if path.extension().unwrap_or_default() != "rs" {
+            continue;
+        }
+        let name = {
+            let file_name = path.file_name().unwrap().to_str().unwrap();
+            file_name[5..file_name.len() - 3].to_string()
+        };
+        let text = fs::read_to_string(&path)?;
+        let test = Test { name: name.clone(), text, ok };
+        if let Some(old) = res.insert(name, (path, test)) {
+            println!("Duplicate test: {:?}", old);
+        }
+    }
+    Ok(res)
+}
+
+/// A helper to update file on disk if it has changed.
+/// With verify = false,
+pub fn update(path: &Path, contents: &str, mode: Mode) -> Result<()> {
+    match fs::read_to_string(path) {
+        Ok(ref old_contents) if old_contents == contents => {
+            return Ok(());
+        }
+        _ => (),
+    }
+    if mode == Verify {
+        Err(format!("`{}` is not up-to-date", path.display()))?;
+    }
+    eprintln!("updating {}", path.display());
+    fs::write(path, contents)?;
+    Ok(())
+}
diff --git a/xtask/src/main.rs b/xtask/src/main.rs
new file mode 100644
index 000000000..623058436
--- /dev/null
+++ b/xtask/src/main.rs
@@ -0,0 +1,218 @@
+//! FIXME: write short doc here
+
+mod help;
+
+use core::fmt::Write;
+use core::str;
+use pico_args::Arguments;
+use std::{env, path::PathBuf};
+use xtask::{
+    gen_tests, generate_boilerplate, install_format_hook, run, run_clippy, run_fuzzer, run_rustfmt,
+    Cmd, Overwrite, Result,
+};
+
+struct InstallOpt {
+    client: Option<ClientOpt>,
+    server: Option<ServerOpt>,
+}
+
+enum ClientOpt {
+    VsCode,
+}
+
+struct ServerOpt {
+    jemalloc: bool,
+}
+
+fn main() -> Result<()> {
+    let subcommand = match std::env::args_os().nth(1) {
+        None => {
+            eprintln!("{}", help::GLOBAL_HELP);
+            return Ok(());
+        }
+        Some(s) => s,
+    };
+    let mut matches = Arguments::from_vec(std::env::args_os().skip(2).collect());
+    let subcommand = &*subcommand.to_string_lossy();
+    match subcommand {
+        "install" => {
+            if matches.contains(["-h", "--help"]) {
+                eprintln!("{}", help::INSTALL_HELP);
+                return Ok(());
+            }
+            let server = matches.contains("--server");
+            let client_code = matches.contains("--client-code");
+            if server && client_code {
+                eprintln!("{}", help::INSTALL_RA_CONFLICT);
+                return Ok(());
+            }
+            let jemalloc = matches.contains("--jemalloc");
+            matches.finish().or_else(handle_extra_flags)?;
+            let opts = InstallOpt {
+                client: if server { None } else { Some(ClientOpt::VsCode) },
+                server: if client_code { None } else { Some(ServerOpt { jemalloc: jemalloc }) },
+            };
+            install(opts)?
+        }
+        "gen-tests" => {
+            if matches.contains(["-h", "--help"]) {
+                help::print_no_param_subcommand_help(&subcommand);
+                return Ok(());
+            }
+            gen_tests(Overwrite)?
+        }
+        "codegen" => {
+            if matches.contains(["-h", "--help"]) {
+                help::print_no_param_subcommand_help(&subcommand);
+                return Ok(());
+            }
+            generate_boilerplate(Overwrite)?
+        }
+        "format" => {
+            if matches.contains(["-h", "--help"]) {
+                help::print_no_param_subcommand_help(&subcommand);
+                return Ok(());
+            }
+            run_rustfmt(Overwrite)?
+        }
+        "format-hook" => {
+            if matches.contains(["-h", "--help"]) {
+                help::print_no_param_subcommand_help(&subcommand);
+                return Ok(());
+            }
+            install_format_hook()?
+        }
+        "lint" => {
+            if matches.contains(["-h", "--help"]) {
+                help::print_no_param_subcommand_help(&subcommand);
+                return Ok(());
+            }
+            run_clippy()?
+        }
+        "fuzz-tests" => {
+            if matches.contains(["-h", "--help"]) {
+                help::print_no_param_subcommand_help(&subcommand);
+                return Ok(());
+            }
+            run_fuzzer()?
+        }
+        _ => eprintln!("{}", help::GLOBAL_HELP),
+    }
+    Ok(())
+}
+
+fn handle_extra_flags(e: pico_args::Error) -> Result<()> {
+    if let pico_args::Error::UnusedArgsLeft(flags) = e {
+        let mut invalid_flags = String::new();
+        for flag in flags {
+            write!(&mut invalid_flags, "{}, ", flag)?;
+        }
+        let (invalid_flags, _) = invalid_flags.split_at(invalid_flags.len() - 2);
+        Err(format!("Invalid flags: {}", invalid_flags).into())
+    } else {
+        Err(e.to_string().into())
+    }
+}
+
+fn install(opts: InstallOpt) -> Result<()> {
+    if cfg!(target_os = "macos") {
+        fix_path_for_mac()?
+    }
+    if let Some(server) = opts.server {
+        install_server(server)?;
+    }
+    if let Some(client) = opts.client {
+        install_client(client)?;
+    }
+    Ok(())
+}
+
+fn fix_path_for_mac() -> Result<()> {
+    let mut vscode_path: Vec<PathBuf> = {
+        const COMMON_APP_PATH: &str =
+            r"/Applications/Visual Studio Code.app/Contents/Resources/app/bin";
+        const ROOT_DIR: &str = "";
+        let home_dir = match env::var("HOME") {
+            Ok(home) => home,
+            Err(e) => Err(format!("Failed getting HOME from environment with error: {}.", e))?,
+        };
+
+        [ROOT_DIR, &home_dir]
+            .iter()
+            .map(|dir| String::from(*dir) + COMMON_APP_PATH)
+            .map(PathBuf::from)
+            .filter(|path| path.exists())
+            .collect()
+    };
+
+    if !vscode_path.is_empty() {
+        let vars = match env::var_os("PATH") {
+            Some(path) => path,
+            None => Err("Could not get PATH variable from env.")?,
+        };
+
+        let mut paths = env::split_paths(&vars).collect::<Vec<_>>();
+        paths.append(&mut vscode_path);
+        let new_paths = env::join_paths(paths)?;
+        env::set_var("PATH", &new_paths);
+    }
+
+    Ok(())
+}
+
+fn install_client(ClientOpt::VsCode: ClientOpt) -> Result<()> {
+    Cmd { unix: r"npm ci", windows: r"cmd.exe /c npm.cmd ci", work_dir: "./editors/code" }.run()?;
+    Cmd {
+        unix: r"npm run package",
+        windows: r"cmd.exe /c npm.cmd run package",
+        work_dir: "./editors/code",
+    }
+    .run()?;
+
+    let code_binary = ["code", "code-insiders", "codium"].iter().find(|bin| {
+        Cmd {
+            unix: &format!("{} --version", bin),
+            windows: &format!("cmd.exe /c {}.cmd --version", bin),
+            work_dir: "./editors/code",
+        }
+        .run()
+        .is_ok()
+    });
+
+    let code_binary = match code_binary {
+        Some(it) => it,
+        None => Err("Can't execute `code --version`. Perhaps it is not in $PATH?")?,
+    };
+
+    Cmd {
+        unix: &format!(r"{} --install-extension ./ra-lsp-0.0.1.vsix --force", code_binary),
+        windows: &format!(
+            r"cmd.exe /c {}.cmd --install-extension ./ra-lsp-0.0.1.vsix --force",
+            code_binary
+        ),
+        work_dir: "./editors/code",
+    }
+    .run()?;
+
+    let output = Cmd {
+        unix: &format!(r"{} --list-extensions", code_binary),
+        windows: &format!(r"cmd.exe /c {}.cmd --list-extensions", code_binary),
+        work_dir: ".",
+    }
+    .run_with_output()?;
+
+    if !str::from_utf8(&output.stdout)?.contains("ra-lsp") {
+        Err("Could not install the Visual Studio Code extension. \
+             Please make sure you have at least NodeJS 10.x installed and try again.")?;
+    }
+
+    Ok(())
+}
+
+fn install_server(opts: ServerOpt) -> Result<()> {
+    if opts.jemalloc {
+        run("cargo install --path crates/ra_lsp_server --locked --force --features jemalloc", ".")
+    } else {
+        run("cargo install --path crates/ra_lsp_server --locked --force", ".")
+    }
+}