1 files changed, 149 insertions, 0 deletions
diff --git a/nix/nint/nint.rs b/nix/nint/nint.rs
new file mode 100644
index 000000000000..abb0153c3ad2
--- /dev/null
+++ b/nix/nint/nint.rs
@@ -0,0 +1,149 @@
+extern crate serde_json;
+
+use serde_json::Value;
+use std::convert::TryFrom;
+use std::ffi::OsString;
+use std::io::{stderr, stdout, Error, ErrorKind, Write};
+use std::os::unix::ffi::{OsStrExt, OsStringExt};
+use std::process::Command;
+
+fn render_nix_string(s: &OsString) -> OsString {
+    let mut rendered = Vec::new();
+
+    rendered.extend(b"\"");
+
+    for b in s.as_os_str().as_bytes() {
+        match char::from(*b) {
+            '\"' => rendered.extend(b"\\\""),
+            '\\' => rendered.extend(b"\\\\"),
+            '$' => rendered.extend(b"\\$"),
+            _ => rendered.push(*b),
+        }
+    }
+
+    rendered.extend(b"\"");
+
+    OsString::from_vec(rendered)
+}
+
+fn render_nix_list(arr: &[OsString]) -> OsString {
+    let mut rendered = Vec::new();
+
+    rendered.extend(b"[ ");
+
+    for el in arr {
+        rendered.extend(render_nix_string(el).as_os_str().as_bytes());
+        rendered.extend(b" ");
+    }
+
+    rendered.extend(b"]");
+
+    OsString::from_vec(rendered)
+}
+
+/// Slightly overkill helper macro which takes a `Map<String, Value>` obtained
+/// from `Value::Object` and an output name (`stderr` or `stdout`) as an
+/// identifier. If a value exists for the given output in the object it gets
+/// written to the appropriate output.
+macro_rules! handle_set_output {
+    ($map_name:ident, $output_name:ident) => {
+        match $map_name.get(stringify!($output_name)) {
+            Some(Value::String(s)) => $output_name().write_all(s.as_bytes()),
+            Some(_) => Err(Error::new(
+                ErrorKind::Other,
+                format!("Attribute {} must be a string!", stringify!($output_name)),
+            )),
+            None => Ok(()),
+        }
+    };
+}
+
+fn main() -> std::io::Result<()> {
+    let mut nix_args = Vec::new();
+
+    let mut args = std::env::args_os().into_iter();
+    let mut in_args = true;
+
+    let mut argv: Vec<OsString> = Vec::new();
+
+    // skip argv[0]
+    args.next();
+
+    loop {
+        let arg = match args.next() {
+            Some(a) => a,
+            None => break,
+        };
+
+        if !arg.to_str().map(|s| s.starts_with("-")).unwrap_or(false) {
+            in_args = false;
+        }
+
+        if in_args {
+            match (arg.to_str()) {
+                Some("--arg") | Some("--argstr") => {
+                    nix_args.push(arg);
+                    nix_args.push(args.next().unwrap());
+                    nix_args.push(args.next().unwrap());
+                    Ok(())
+                }
+                _ => Err(Error::new(ErrorKind::Other, "unknown argument")),
+            }?
+        } else {
+            argv.push(arg);
+        }
+    }
+
+    if argv.len() < 1 {
+        Err(Error::new(ErrorKind::Other, "missing argv"))
+    } else {
+        let cd = std::env::current_dir()?.into_os_string();
+
+        nix_args.push(OsString::from("--arg"));
+        nix_args.push(OsString::from("currentDir"));
+        nix_args.push(cd);
+
+        nix_args.push(OsString::from("--arg"));
+        nix_args.push(OsString::from("argv"));
+        nix_args.push(render_nix_list(&argv[..]));
+
+        nix_args.push(OsString::from("--eval"));
+        nix_args.push(OsString::from("--strict"));
+        nix_args.push(OsString::from("--json"));
+
+        nix_args.push(argv[0].clone());
+
+        let run = Command::new("nix-instantiate").args(nix_args).output()?;
+
+        match serde_json::from_slice(&run.stdout[..]) {
+            Ok(Value::String(s)) => stdout().write_all(s.as_bytes()),
+            Ok(Value::Object(m)) => {
+                handle_set_output!(m, stdout)?;
+                handle_set_output!(m, stderr)?;
+
+                match m.get("exit") {
+                    Some(Value::Number(n)) => {
+                        let code = n.as_i64().and_then(|v| i32::try_from(v).ok());
+
+                        match code {
+                            Some(i) => std::process::exit(i),
+                            None => {
+                                Err(Error::new(ErrorKind::Other, "Attribute exit is not an i32"))
+                            }
+                        }
+                    }
+                    Some(_) => Err(Error::new(ErrorKind::Other, "exit must be a number")),
+                    None => Ok(()),
+                }
+            }
+            Ok(_) => Err(Error::new(
+                ErrorKind::Other,
+                "output must be a string or an object",
+            )),
+            _ => {
+                stderr().write_all(&run.stderr[..]);
+                Err(Error::new(ErrorKind::Other, "internal nix error"))
+            }
+        }
+    }
+}