feat(tvix): set up a simple command line parser for nix-store r/3522

We are going to have a 1:1 drop-in replacement for the old-style nix
tools, and this starts implementing the cli parser part.

The first step is to have a simple integration test suite that can
verify that we match the nix CLI.

clap is a super complicated parsing library, but looking through the
rest they are either too opinioated to be of use for us, or depend on
clap as implementation.

Change-Id: I4cf6051f3a4f782c3242fd0d2b9eab3fbe33d8ad
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4756
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: Profpatsch <mail@profpatsch.de>

1 files changed, 102 insertions, 2 deletions

diff --git a/tvix/src/bin/nix-store.rs b/tvix/src/bin/nix-store.rs
index 7bf5442cb9..72e3bb2204 100644
--- a/tvix/src/bin/nix-store.rs
+++ b/tvix/src/bin/nix-store.rs
@@ -1,3 +1,103 @@
-fn main () {
-  println!("hello, nix");
+fn main() {
+    main_args(std::env::args().collect()).unwrap_or_else(|e| e.exit());
+}
+
+pub fn main_args(args: Vec<String>) -> clap::Result<NixResult> {
+    let matches = clap::App::new("nix-store")
+        .subcommand(clap::App::new("--add").arg(clap::Arg::new("FILE").required(true).index(1)))
+        .try_get_matches_from(args.iter())?;
+    if let Some(add) = matches.subcommand_matches("--add") {
+        let file = add.value_of("FILE").expect("--add needs a file");
+        let file_contents =
+            std::fs::read_to_string(file).expect(&format!("file {} does not exist", file));
+        Ok(NixResult::FileAddedToStore {
+            content: file_contents,
+        })
+    } else {
+        panic!("read some arguments that we do not know: {:?}", args)
+    }
+}
+
+#[derive(Debug, Eq, PartialEq)]
+pub enum NixResult {
+    FileAddedToStore { content: String },
+}
+
+#[cfg(test)]
+mod integration_tests {
+    use std::{collections::VecDeque, io::Write};
+
+    use super::*;
+
+    #[derive(Debug)]
+    enum NixOutput {
+        Err {
+            status: i32,
+            stdout: String,
+            stderr: String,
+        },
+        Ok {
+            stdout: String,
+            stderr: String,
+        },
+    }
+
+    fn run_nix_command(cmd: &str, args: Vec<String>) -> NixOutput {
+        let out = std::process::Command::new(cmd)
+            .args(args)
+            .output()
+            .expect(&format!("could not run {}", cmd));
+        match out.status.code().expect("no status code!") {
+            0 => NixOutput::Ok {
+                stdout: String::from_utf8_lossy(&out.stdout).trim_end().to_string(),
+                stderr: String::from_utf8_lossy(&out.stderr).trim_end().to_string(),
+            },
+            status => NixOutput::Err {
+                status,
+                stdout: String::from_utf8_lossy(&out.stdout).trim_end().to_string(),
+                stderr: String::from_utf8_lossy(&out.stderr).trim_end().to_string(),
+            },
+        }
+    }
+
+    fn nix_nix_store<'a>(args: Vec<String>) -> NixResult {
+        match run_nix_command("nix-store", args) {
+            err @ NixOutput::Err { .. } => panic!("nix-store --add failed: {:#?}", err),
+            NixOutput::Ok { stdout, .. } => NixResult::FileAddedToStore {
+                content: std::fs::read_to_string(&stdout)
+                    .expect(&format!("cannot open {} as store file", stdout)),
+            },
+        }
+    }
+
+    fn tvix_nix_store<'a>(args: Vec<String>) -> NixResult {
+        eprintln!("running tvix with arguments {:?}", args);
+        let mut args = VecDeque::from(args);
+        args.push_front("tvix-store".to_string());
+        super::main_args(Vec::from(args))
+            .unwrap_or_else(|e| panic!("clap command line parsing failed:\n{}", e))
+    }
+
+    #[test]
+    fn test_nix_store_add() {
+        let file_content = "I am a copied file";
+        let mut tempfile = tempfile::NamedTempFile::new().expect("cannot create temp file");
+        tempfile
+            .write_all(file_content.as_bytes())
+            .expect("could not write to tempfile");
+        assert_eq!(
+            tvix_nix_store(vec![
+                "--add".to_string(),
+                tempfile.path().as_os_str().to_string_lossy().into_owned()
+            ]),
+            nix_nix_store(vec![
+                "--add".to_string(),
+                tempfile.path().as_os_str().to_string_lossy().into_owned()
+            ]),
+            "added file contents were not the same"
+        );
+
+        // make sure the tempfile lives till here
+        drop(tempfile)
+    }
 }