Make it build on windows (#5)

.gitattributes

@@ -0,0 +1,8 @@
+build                   symlink=dir
+buildtools              symlink=dir
+build_overrides         symlink=dir
+testing                 symlink=dir
+third_party/googletest  symlink=dir
+third_party/jinja2      symlink=dir
+third_party/llvm-build  symlink=dir
+third_party/markupsafe  symlink=dir

.github/workflows/ci.yml

@@ -9,7 +9,7 @@ jobs:
     timeout-minutes: 60
     strategy:
       matrix:
-        os: [macOS-10.14, ubuntu-16.04] # TODO(ry) windows-2019
+        os: [macOS-10.14, ubuntu-16.04, windows-2019]
     steps:
       - name: Configure git
         run: git config --global core.symlinks true
@@ -30,6 +30,20 @@ jobs:
         with:
           python-version: "2.7.16"
 
+      - name: Remove unused versions of Python
+        # Depot_tools bootstraps its own copy of virtualenv. This fails on
+        # windows when multiple versions of python are in present in PATH,
+        # so we remove all but the first one.
+        # 🤯 Removing items from PATH does not seem possible on Github Actions,
+        # not even by using `echo ::set-env name=PATH`, so we have to rename
+        # or delete the actual Python directories.
+        if: startsWith(matrix.os, 'windows')
+        run: |-
+          $env:PATH -split ";" |
+            Where-Object { Test-Path "$_\python.exe" } |
+            Select-Object -Skip 1 |
+            ForEach-Object { Move-Item "$_" "$_.disabled" }
+
       - name: Environment (common)
         run: |
           echo ::set-env name=GH_ACTIONS::1
@@ -59,13 +73,9 @@ jobs:
       - name: Environment (windows)
         if: startsWith(matrix.os, 'windows')
         run: |
-          # These appear unnecessary:
-          #choco install curl
-          #choco install archive
           curl -LO https://github.com/mozilla/sccache/releases/download/0.2.12/sccache-0.2.12-x86_64-pc-windows-msvc.tar.gz
           tar -zxvf sccache-0.2.12-x86_64-pc-windows-msvc.tar.gz
           echo ::add-path::$(pwd)\sccache-0.2.12-x86_64-pc-windows-msvc\
-          echo ::add-path::$(pwd)\third_party\depot_tools\
 
       - name: Start sccache
         env:

build.rs

@@ -7,13 +7,17 @@ use std::process::Command;
 use which::which;
 
 fn main() {
+  if cfg!(windows) {
+    init_depot_tools_windows();
+  }
   if !Path::new("third_party/v8/src").is_dir()
     || env::var_os("GCLIENT_SYNC").is_some()
   {
     gclient_sync();
   }
 
-  let mut gn_args = if cargo_gn::is_debug() {
+  // On windows, rustc cannot link with a V8 debug build.
+  let mut gn_args = if cargo_gn::is_debug() && !cfg!(target_os = "windows") {
     vec!["is_debug=true".to_string()]
   } else {
     vec!["is_debug=false".to_string()]
@@ -46,6 +50,39 @@ fn main() {
   }
 }
 
+fn init_depot_tools_windows() {
+  let depot_tools = env::current_dir()
+    .unwrap()
+    .join("third_party")
+    .join("depot_tools");
+  // Bootstrap depot_tools.
+  if !depot_tools.join("git.bat").is_file() {
+    let status = Command::new("cmd.exe")
+      .arg("/c")
+      .arg("bootstrap\\win_tools.bat")
+      .current_dir(&depot_tools)
+      .status()
+      .expect("bootstrapping depot_tools failed");
+    assert!(status.success());
+  }
+  // Add third_party/depot_tools and buildtools/win to PATH.
+  // TODO: this should be done on all platforms.
+  // TODO: buildtools/win should not be added; instead, cargo_gn should invoke
+  // depot_tools/gn.bat.
+  let buildtools_win =
+    env::current_dir().unwrap().join("buildtools").join("win");
+  // Bootstrap depot_tools.
+  let path = env::var_os("PATH").unwrap();
+  let paths = vec![depot_tools, buildtools_win]
+    .into_iter()
+    .chain(env::split_paths(&path))
+    .collect::<Vec<_>>();
+  let path = env::join_paths(paths).unwrap();
+  env::set_var("PATH", &path);
+  // TODO: cargo_gn should do this.
+  env::set_var("DEPOT_TOOLS_WIN_TOOLCHAIN", "0");
+}
+
 fn git_submodule_update() {
   Command::new("git")
     .arg("submodule")