feat(users/Profpatsch): set up a file watcher for tree sitter

Uses inotify to watch a file and print when it is modified, so we can
update the parser and display the sexp on the terminal.

Now the setup is good enough to start experiementing with queries on
the syntax tree.

Change-Id: I091587fc495ff627c79a69a52915aaaa8c51fcd2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2411
Tested-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>

third_party/nixpkgs-exposed/exposed/default.nix

@@ -13,6 +13,7 @@
     avrlibc
     bashInteractive
     bat
+    bc
     buildBazelPackage
     buildFHSUserEnv
     buildGoModule
@@ -44,6 +45,7 @@
     emacsPackagesGen
     execline
     fd
+    fdtools
     fetchFromGitHub
     fetchgit
     fetchurl
@@ -87,9 +89,11 @@
     mkShell
     moreutils
     nano
+    ncurses
     nginx
     ninja
     nix
+    ocamlPackages
     openssh
     openssl
     overrideCC

users/Profpatsch/lib.nix

@@ -1,6 +1,8 @@
 { depot, pkgs, ... }:
 let
-  bins = depot.nix.getBins pkgs.coreutils ["printf" "echo"];
+  bins = depot.nix.getBins pkgs.coreutils [ "printf" "echo" "cat" "printenv" ]
+      // depot.nix.getBins pkgs.fdtools [ "multitee" ]
+      ;
 
   debugExec = msg: depot.nix.writeExecline "debug-exec" {} [
     "if" [
@@ -15,9 +17,19 @@ let
     "fdmove" "-c" "1" "2" bins.printf "$@"
   ];
 
+  eprint-stdin = depot.nix.writeExecline "eprint-stdin" {} [
+    "pipeline" [ bins.multitee "0-1,2" ] "$@"
+  ];
+
+  eprintenv = depot.nix.writeExecline "eprintenv" { readNArgs = 1; } [
+    "fdmove" "-c" "1" "2" bins.printenv "$1"
+  ];
+
 in {
   inherit
     debugExec
     eprintf
+    eprint-stdin
+    eprintenv
     ;
 }

users/Profpatsch/rust-crates.nix

@@ -50,4 +50,36 @@ rec {
     buildDependencies = [ cc ];
     sha256 = "0jwwbvs4icpra7m1ycvnyri5h3sbw4qrfvgnnvnk72h4w93qhzhr";
   };
+
+  libc = pkgs.buildRustCrate {
+    pname = "libc";
+    crateName = "libc";
+    version = "0.2.82";
+    sha256 = "02zgn6c0xwh331hky417lbr29kmvrw3ylxs8822syyhjfjqszvsx";
+  };
+
+  bitflags = pkgs.buildRustCrate {
+    pname = "bitflags";
+    crateName = "bitflags";
+    version = "1.2.1";
+    sha256 = "0b77awhpn7yaqjjibm69ginfn996azx5vkzfjj39g3wbsqs7mkxg";
+  };
+
+  inotify-sys = pkgs.buildRustCrate {
+    pname = "inotify-sys";
+    crateName = "inotify-sys";
+    version = "0.1.5";
+    dependencies = [ libc ];
+    sha256 = "1yiy577xxhi0j90nbg9nkd8cqwc1xix62rz55jjngvxa5jl5613v";
+  };
+
+  inotify = pkgs.buildRustCrate {
+    pname = "inotify";
+    crateName = "inotify";
+    version = "0.9.2";
+    edition = "2018";
+    dependencies = [ bitflags libc inotify-sys ];
+    sha256 = "0fcknyvknglwwk1pdzdlb4m0ry2dym1yx8r5prf2v00pxnjk0hv2";
+  };
+
 }

users/Profpatsch/tree-sitter.nix

@@ -1,15 +1,17 @@
 { depot, pkgs, lib, ... }:
 
 let
+  bins = depot.nix.getBins pkgs.coreutils [ "head" "printf" "cat" ]
+      // depot.nix.getBins pkgs.ncurses [ "tput" ]
+      // depot.nix.getBins pkgs.bc [ "bc" ]
+      // depot.nix.getBins pkgs.ocamlPackages.sexp [ "sexp" ];
+
   print-ast = depot.users.Profpatsch.writers.rustSimple {
     name = "print-ast";
     dependencies = with depot.users.Profpatsch.rust-crates; [
       libloading
       tree-sitter
     ];
-    buildInputs = [
-      pkgs.tree-sitter
-    ];
   } ''
     extern crate libloading;
     extern crate tree_sitter;
@@ -39,9 +41,7 @@ let
       let mut parser = Parser::new();
       let lang = _load_language(so, symbol_name).unwrap();
       parser.set_language(lang).unwrap();
-      let mut bytes = Vec::new();
-      let mut file = std::fs::OpenOptions::new().read(true).open(file).unwrap();
-      file.read_to_end(&mut bytes);
+      let bytes = std::fs::read(&file).unwrap();
       print!("{}", parser.parse(&bytes, None).unwrap().root_node().to_sexp());
     }
 
@@ -58,8 +58,85 @@ let
     };
   };
 
-  parse-nix-file = depot.nix.writeExecline "parse-nix-file" { readNArgs = 1; } [
-    print-ast "${tree-sitter-nix}/parser" "tree_sitter_nix" "$1"
+  watch-file-modified = depot.users.Profpatsch.writers.rustSimple {
+    name = "watch-file-modified";
+    dependencies = [ depot.users.Profpatsch.rust-crates.inotify ];
+  } ''
+    extern crate inotify;
+    use inotify::{EventMask, WatchMask, Inotify};
+    use std::io::Write;
+
+    fn main() {
+        let mut inotify = Inotify::init()
+            .expect("Failed to initialize inotify");
+
+        let file = std::env::args().nth(1).unwrap();
+
+        let file_watch = inotify
+            .add_watch(
+                &file,
+                WatchMask::MODIFY
+            )
+            .expect("Failed to add inotify watch");
+
+        fn to_netstring(s: &[u8]) -> Vec<u8> {
+            let len = s.len();
+            // length of the integer as ascii
+            let i_len = ((len as f64).log10() as usize) + 1;
+            let ns_len = i_len + 1 + len + 1;
+            let mut res = Vec::with_capacity(ns_len);
+            res.extend_from_slice(format!("{}:", len).as_bytes());
+            res.extend_from_slice(s);
+            res.push(b',');
+            res
+        }
+
+        let mut buffer = [0u8; 4096];
+        loop {
+            let events = inotify
+                .read_events_blocking(&mut buffer)
+                .expect("Failed to read inotify events");
+
+            for event in events {
+                if event.wd == file_watch {
+                  std::io::stdout().write(&to_netstring(file.as_bytes()));
+                  std::io::stdout().flush();
+                }
+            }
+        }
+    }
+
+  '';
+
+  # clear screen and set LINES and COLUMNS to terminal height & width
+  clear-screen = depot.nix.writeExecline "clear-screen" {} [
+    "if" [ bins.tput "clear" ]
+    "backtick" "-in" "LINES" [ bins.tput "lines" ]
+    "backtick" "-in" "COLUMNS" [ bins.tput "cols" ]
+    "$@"
+  ];
+
+  print-nix-file = depot.nix.writeExecline "print-nix-file" { readNArgs = 1; } [
+    "pipeline" [ print-ast "${tree-sitter-nix}/parser" "tree_sitter_nix" "$1" ]
+    "pipeline" [ bins.sexp "print" ]
+    clear-screen
+    "importas" "-ui" "lines" "LINES"
+    "backtick" "-in" "ls" [
+      "pipeline"
+        # when you pull out bc to decrement an integer it’s time to switch to python lol
+        [ bins.printf "x=%s; --x\n" "$lines" ]
+        bins.bc
+    ]
+    "importas" "-ui" "l" "ls"
+    bins.head "-n\${l}"
+  ];
+
+  print-nix-file-on-update = depot.nix.writeExecline "print-nix-file-on-update" { readNArgs = 1; } [
+    "if" [ print-nix-file "$1" ]
+    "pipeline" [ watch-file-modified "$1" ]
+    "forstdin" "-d" "" "file"
+    "importas" "file" "file"
+    print-nix-file "$file"
   ];
 
   # copied from nixpkgs
@@ -104,6 +181,7 @@ in {
   inherit
     print-ast
     tree-sitter-nix
-    parse-nix-file
+    print-nix-file-on-update
+    watch-file-modified
     ;
 }