From 03a3189a3d8e3e9d198ccf73bc0a836aaa6b6e3d Mon Sep 17 00:00:00 2001
From: Griffin Smith <root@gws.fyi>
Date: Wed, 12 Oct 2022 18:45:52 -0400
Subject: feat(tvix/eval): Initial impl of builtins.match

Implement an *initial* version of builtins.match, using the rust `regex`
crate for regular expressions. The rust regex crate definitely has
different semantics than nix's regular expressions - but we'd like to
see how far we can get before the incompatibility starts to matter.

This consciously leaves out any sort of memo for compiled regular
expressions (which upstream nix also has) for the sake of expediency -
in the future we should implement that so we don't have to compile the
same regular expression multiple times.

Change-Id: I5b718635831ec83397940e417a9047c4342b6fa1
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6989
Tested-by: BuildkiteCI
Reviewed-by: Adam Joseph <adam@westernsemico.com>
Reviewed-by: tazjin <tazjin@tvl.su>
---
 tvix/eval/Cargo.lock                               | 12 +++++++++
 tvix/eval/Cargo.toml                               |  1 +
 tvix/eval/src/builtins/mod.rs                      | 20 +++++++++++++++
 .../src/tests/tvix_tests/eval-okay-regex-match.exp |  1 +
 .../src/tests/tvix_tests/eval-okay-regex-match.nix | 29 ++++++++++++++++++++++
 5 files changed, 63 insertions(+)
 create mode 100644 tvix/eval/src/tests/tvix_tests/eval-okay-regex-match.exp
 create mode 100644 tvix/eval/src/tests/tvix_tests/eval-okay-regex-match.nix

(limited to 'tvix/eval')

diff --git a/tvix/eval/Cargo.lock b/tvix/eval/Cargo.lock
index b9fa3d3a11da..5e9aaa08679b 100644
--- a/tvix/eval/Cargo.lock
+++ b/tvix/eval/Cargo.lock
@@ -2,6 +2,15 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "aho-corasick"
+version = "0.7.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b4f55bd91a0978cbfd91c457a164bab8b4001c833b7f323132c0a4e1922dd44e"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "atty"
 version = "0.2.14"
@@ -859,6 +868,8 @@ version = "1.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4c4eb3267174b8c6c2f654116623910a0fef09c4753f8dd83db29c48a0df988b"
 dependencies = [
+ "aho-corasick",
+ "memchr",
  "regex-syntax",
 ]
 
@@ -1208,6 +1219,7 @@ dependencies = [
  "path-clean",
  "pretty_assertions",
  "proptest",
+ "regex",
  "rnix",
  "rowan",
  "rustyline",
diff --git a/tvix/eval/Cargo.toml b/tvix/eval/Cargo.toml
index 67ed42609deb..3c6213c21520 100644
--- a/tvix/eval/Cargo.toml
+++ b/tvix/eval/Cargo.toml
@@ -25,6 +25,7 @@ proptest = { version = "1.0.0", default_features = false, features = ["std", "al
 test-strategy = { version = "0.2.1", optional = true }
 clap = { version = "3.2.22", optional = true, features = ["derive", "env"] }
 serde_json = "1.0.86"
+regex = "1.6.0"
 
 # rnix has not been released in a while (as of 2022-09-23), we will
 # use it from git.
diff --git a/tvix/eval/src/builtins/mod.rs b/tvix/eval/src/builtins/mod.rs
index c0dce868c6fc..0082d36d5735 100644
--- a/tvix/eval/src/builtins/mod.rs
+++ b/tvix/eval/src/builtins/mod.rs
@@ -7,6 +7,8 @@ use std::cmp;
 use std::collections::{BTreeMap, HashMap, HashSet};
 use std::path::PathBuf;
 
+use regex::Regex;
+
 use crate::{
     errors::ErrorKind,
     value::{Builtin, CoercionKind, NixAttrs, NixList, NixString, Value},
@@ -381,6 +383,24 @@ fn pure_builtins() -> Vec<Builtin> {
                 .map(|list| Value::List(NixList::from(list)))
                 .map_err(Into::into)
         }),
+        Builtin::new(
+            "match",
+            &[true, true],
+            |mut args: Vec<Value>, _: &mut VM| {
+                let s = args.pop().unwrap().to_str()?;
+                let re = args.pop().unwrap().to_str()?;
+                let re: Regex = Regex::new(&format!("^{}$", re.as_str())).unwrap();
+                match re.captures(&s) {
+                    Some(caps) => Ok(caps
+                        .iter()
+                        .skip(1)
+                        .map(|grp| grp.map(|g| Value::from(g.as_str())).unwrap_or(Value::Null))
+                        .collect::<Vec<Value>>()
+                        .into()),
+                    None => Ok(Value::Null),
+                }
+            },
+        ),
         Builtin::new(
             "mul",
             &[false, false],
diff --git a/tvix/eval/src/tests/tvix_tests/eval-okay-regex-match.exp b/tvix/eval/src/tests/tvix_tests/eval-okay-regex-match.exp
new file mode 100644
index 000000000000..950103539123
--- /dev/null
+++ b/tvix/eval/src/tests/tvix_tests/eval-okay-regex-match.exp
@@ -0,0 +1 @@
+[ true true false true true true true false false true false [ "foobar" ] [ "FOO" ] [ "/path/to/" "/path/to" "foobar" "nix" ] [ null null "foobar" "cc" ] ]
diff --git a/tvix/eval/src/tests/tvix_tests/eval-okay-regex-match.nix b/tvix/eval/src/tests/tvix_tests/eval-okay-regex-match.nix
new file mode 100644
index 000000000000..f774e00a215a
--- /dev/null
+++ b/tvix/eval/src/tests/tvix_tests/eval-okay-regex-match.nix
@@ -0,0 +1,29 @@
+with builtins;
+
+let
+
+  matches = pat: s: match pat s != null;
+
+  splitFN = match "((.*)/)?([^/]*)\\.(nix|cc)";
+
+in
+
+[
+  (matches "foobar" "foobar")
+  (matches "fo*" "f")
+  (matches "fo+" "f")
+  (matches "fo*" "fo")
+  (matches "fo*" "foo")
+  (matches "fo+" "foo")
+  (matches "fo{1,2}" "foo")
+  (matches "fo{1,2}" "fooo")
+  (matches "fo*" "foobar")
+  (matches "[[:space:]]+([^[:space:]]+)[[:space:]]+" "  foo   ")
+  (matches "[[:space:]]+([[:upper:]]+)[[:space:]]+" "  foo   ")
+
+  (match "(.*)\\.nix" "foobar.nix")
+  (match "[[:space:]]+([[:upper:]]+)[[:space:]]+" "  FOO   ")
+
+  (splitFN "/path/to/foobar.nix")
+  (splitFN "foobar.cc")
+]
-- 
cgit 1.4.1