diff options
Diffstat (limited to '')
-rw-r--r-- | nix/nint/README.md | 12 | ||||
-rw-r--r-- | nix/nint/nint.rs | 48 |
2 files changed, 57 insertions, 3 deletions
diff --git a/nix/nint/README.md b/nix/nint/README.md index ddd8045f7378..369a8276199a 100644 --- a/nix/nint/README.md +++ b/nix/nint/README.md @@ -15,8 +15,16 @@ to the following calling convention: program name at `builtins.head argv`. * Extra arguments can be manually passed as described below. -* The return value should always be a string (throwing is also okay) - which is printed to stdout by `nint`. +* The return value must either be + + * A string which is rendered to `stdout`. + + * An attribute set with the following optional attributes: + + * `stdout`: A string that's rendered to `stdout` + * `stderr`: A string that's rendered to `stderr` + * `exit`: A number which is used as an exit code. + If missing, nint always exits with 0 (or equivalent). ## Usage diff --git a/nix/nint/nint.rs b/nix/nint/nint.rs index 823de4865565..1fa4dccb4f86 100644 --- a/nix/nint/nint.rs +++ b/nix/nint/nint.rs @@ -5,6 +5,7 @@ use std::ffi::OsString; use std::os::unix::ffi::{OsStringExt, OsStrExt}; use std::io::{Error, ErrorKind, Write, stdout, stderr}; use std::process::Command; +use std::convert::{TryFrom}; fn render_nix_string(s: &OsString) -> OsString { let mut rendered = Vec::new(); @@ -40,6 +41,26 @@ fn render_nix_list(arr: &[OsString]) -> OsString { 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(); @@ -90,6 +111,7 @@ fn main() -> std::io::Result<()> { 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()); @@ -100,7 +122,31 @@ fn main() -> std::io::Result<()> { match serde_json::from_slice(&run.stdout[..]) { Ok(Value::String(s)) => stdout().write_all(s.as_bytes()), - Ok(_) => Err(Error::new(ErrorKind::Other, "output must be a string")), + 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")) |