refactor(tvix/nix-compat): absorb //tvix/derivation r/5791

Put this in its src/derivation.

Change-Id: Ic047ab1c2da555a833ee454e10ef60c77537b617
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7967
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Autosubmit: flokli <flokli@flokli.de>

17 files changed, 521 insertions, 0 deletions

diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv b/tvix/nix-compat/src/derivation/tests/derivation_tests/0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv
new file mode 100644
index 000000000000..a4fea3c5f486
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv
@@ -0,0 +1 @@
+Derive([("out","/nix/store/4q0pg5zpfmznxscq3avycvf9xdvx50n3-bar","r:sha256","08813cbee9903c62be4c5027726a418a300da4500b2d369d3af9286f4815ceba")],[],[],":",":",[],[("builder",":"),("name","bar"),("out","/nix/store/4q0pg5zpfmznxscq3avycvf9xdvx50n3-bar"),("outputHash","08813cbee9903c62be4c5027726a418a300da4500b2d369d3af9286f4815ceba"),("outputHashAlgo","sha256"),("outputHashMode","recursive"),("system",":")])
\ No newline at end of file
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv.json b/tvix/nix-compat/src/derivation/tests/derivation_tests/0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv.json
new file mode 100644
index 000000000000..c8bbc4cbb5be
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv.json
@@ -0,0 +1,23 @@
+{
+  "args": [],
+  "builder": ":",
+  "env": {
+    "builder": ":",
+    "name": "bar",
+    "out": "/nix/store/4q0pg5zpfmznxscq3avycvf9xdvx50n3-bar",
+    "outputHash": "08813cbee9903c62be4c5027726a418a300da4500b2d369d3af9286f4815ceba",
+    "outputHashAlgo": "sha256",
+    "outputHashMode": "recursive",
+    "system": ":"
+  },
+  "inputDrvs": {},
+  "inputSrcs": [],
+  "outputs": {
+    "out": {
+      "hash": "08813cbee9903c62be4c5027726a418a300da4500b2d369d3af9286f4815ceba",
+      "hashAlgo": "r:sha256",
+      "path": "/nix/store/4q0pg5zpfmznxscq3avycvf9xdvx50n3-bar"
+    }
+  },
+  "system": ":"
+}
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/292w8yzv5nn7nhdpxcs8b7vby2p27s09-nested-json.drv b/tvix/nix-compat/src/derivation/tests/derivation_tests/292w8yzv5nn7nhdpxcs8b7vby2p27s09-nested-json.drv
new file mode 100644
index 000000000000..f0d9230a5a52
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/292w8yzv5nn7nhdpxcs8b7vby2p27s09-nested-json.drv
@@ -0,0 +1 @@
+Derive([("out","/nix/store/pzr7lsd3q9pqsnb42r9b23jc5sh8irvn-nested-json","","")],[],[],":",":",[],[("builder",":"),("json","{\"hello\":\"moto\\n\"}"),("name","nested-json"),("out","/nix/store/pzr7lsd3q9pqsnb42r9b23jc5sh8irvn-nested-json"),("system",":")])
\ No newline at end of file
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/292w8yzv5nn7nhdpxcs8b7vby2p27s09-nested-json.drv.json b/tvix/nix-compat/src/derivation/tests/derivation_tests/292w8yzv5nn7nhdpxcs8b7vby2p27s09-nested-json.drv.json
new file mode 100644
index 000000000000..9cb0b43b4c09
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/292w8yzv5nn7nhdpxcs8b7vby2p27s09-nested-json.drv.json
@@ -0,0 +1,19 @@
+{
+  "args": [],
+  "builder": ":",
+  "env": {
+    "builder": ":",
+    "json": "{\"hello\":\"moto\\n\"}",
+    "name": "nested-json",
+    "out": "/nix/store/pzr7lsd3q9pqsnb42r9b23jc5sh8irvn-nested-json",
+    "system": ":"
+  },
+  "inputDrvs": {},
+  "inputSrcs": [],
+  "outputs": {
+    "out": {
+      "path": "/nix/store/pzr7lsd3q9pqsnb42r9b23jc5sh8irvn-nested-json"
+    }
+  },
+  "system": ":"
+}
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/4wvvbi4jwn0prsdxb7vs673qa5h9gr7x-foo.drv b/tvix/nix-compat/src/derivation/tests/derivation_tests/4wvvbi4jwn0prsdxb7vs673qa5h9gr7x-foo.drv
new file mode 100644
index 000000000000..a2cf9d31f92e
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/4wvvbi4jwn0prsdxb7vs673qa5h9gr7x-foo.drv
@@ -0,0 +1 @@
+Derive([("out","/nix/store/5vyvcwah9l9kf07d52rcgdk70g2f4y13-foo","","")],[("/nix/store/0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv",["out"])],[],":",":",[],[("bar","/nix/store/4q0pg5zpfmznxscq3avycvf9xdvx50n3-bar"),("builder",":"),("name","foo"),("out","/nix/store/5vyvcwah9l9kf07d52rcgdk70g2f4y13-foo"),("system",":")])
\ No newline at end of file
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/4wvvbi4jwn0prsdxb7vs673qa5h9gr7x-foo.drv.json b/tvix/nix-compat/src/derivation/tests/derivation_tests/4wvvbi4jwn0prsdxb7vs673qa5h9gr7x-foo.drv.json
new file mode 100644
index 000000000000..957a85ccab82
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/4wvvbi4jwn0prsdxb7vs673qa5h9gr7x-foo.drv.json
@@ -0,0 +1,23 @@
+{
+  "args": [],
+  "builder": ":",
+  "env": {
+    "bar": "/nix/store/4q0pg5zpfmznxscq3avycvf9xdvx50n3-bar",
+    "builder": ":",
+    "name": "foo",
+    "out": "/nix/store/5vyvcwah9l9kf07d52rcgdk70g2f4y13-foo",
+    "system": ":"
+  },
+  "inputDrvs": {
+    "/nix/store/0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv": [
+      "out"
+    ]
+  },
+  "inputSrcs": [],
+  "outputs": {
+    "out": {
+      "path": "/nix/store/5vyvcwah9l9kf07d52rcgdk70g2f4y13-foo"
+    }
+  },
+  "system": ":"
+}
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/52a9id8hx688hvlnz4d1n25ml1jdykz0-unicode.drv b/tvix/nix-compat/src/derivation/tests/derivation_tests/52a9id8hx688hvlnz4d1n25ml1jdykz0-unicode.drv
new file mode 100644
index 000000000000..bbe88c02c739
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/52a9id8hx688hvlnz4d1n25ml1jdykz0-unicode.drv
@@ -0,0 +1 @@
+Derive([("out","/nix/store/vgvdj6nf7s8kvfbl2skbpwz9kc7xjazc-unicode","","")],[],[],":",":",[],[("builder",":"),("letters","räksmörgås\nrødgrød med fløde\nLübeck\n肥猪\nこんにちは / 今日は\n🌮\n"),("name","unicode"),("out","/nix/store/vgvdj6nf7s8kvfbl2skbpwz9kc7xjazc-unicode"),("system",":")])
\ No newline at end of file
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/52a9id8hx688hvlnz4d1n25ml1jdykz0-unicode.drv.json b/tvix/nix-compat/src/derivation/tests/derivation_tests/52a9id8hx688hvlnz4d1n25ml1jdykz0-unicode.drv.json
new file mode 100644
index 000000000000..f8f33c1bba17
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/52a9id8hx688hvlnz4d1n25ml1jdykz0-unicode.drv.json
@@ -0,0 +1,19 @@
+{
+  "outputs": {
+    "out": {
+      "path": "/nix/store/vgvdj6nf7s8kvfbl2skbpwz9kc7xjazc-unicode"
+    }
+  },
+  "inputSrcs": [],
+  "inputDrvs": {},
+  "system": ":",
+  "builder": ":",
+  "args": [],
+  "env": {
+    "builder": ":",
+    "letters": "räksmörgås\nrødgrød med fløde\nLübeck\n肥猪\nこんにちは / 今日は\n🌮\n",
+    "name": "unicode",
+    "out": "/nix/store/vgvdj6nf7s8kvfbl2skbpwz9kc7xjazc-unicode",
+    "system": ":"
+  }
+}
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/9lj1lkjm2ag622mh4h9rpy6j607an8g2-structured-attrs.drv b/tvix/nix-compat/src/derivation/tests/derivation_tests/9lj1lkjm2ag622mh4h9rpy6j607an8g2-structured-attrs.drv
new file mode 100644
index 000000000000..4b9338c0b953
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/9lj1lkjm2ag622mh4h9rpy6j607an8g2-structured-attrs.drv
@@ -0,0 +1 @@
+Derive([("out","/nix/store/6a39dl014j57bqka7qx25k0vb20vkqm6-structured-attrs","","")],[],[],":",":",[],[("__json","{\"builder\":\":\",\"name\":\"structured-attrs\",\"system\":\":\"}"),("out","/nix/store/6a39dl014j57bqka7qx25k0vb20vkqm6-structured-attrs")])
\ No newline at end of file
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/9lj1lkjm2ag622mh4h9rpy6j607an8g2-structured-attrs.drv.json b/tvix/nix-compat/src/derivation/tests/derivation_tests/9lj1lkjm2ag622mh4h9rpy6j607an8g2-structured-attrs.drv.json
new file mode 100644
index 000000000000..74e3d7df55c5
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/9lj1lkjm2ag622mh4h9rpy6j607an8g2-structured-attrs.drv.json
@@ -0,0 +1,16 @@
+{
+  "args": [],
+  "builder": ":",
+  "env": {
+    "__json": "{\"builder\":\":\",\"name\":\"structured-attrs\",\"system\":\":\"}",
+    "out": "/nix/store/6a39dl014j57bqka7qx25k0vb20vkqm6-structured-attrs"
+  },
+  "inputDrvs": {},
+  "inputSrcs": [],
+  "outputs": {
+    "out": {
+      "path": "/nix/store/6a39dl014j57bqka7qx25k0vb20vkqm6-structured-attrs"
+    }
+  },
+  "system": ":"
+}
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv b/tvix/nix-compat/src/derivation/tests/derivation_tests/ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv
new file mode 100644
index 000000000000..1699c2a75e48
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv
@@ -0,0 +1 @@
+Derive([("out","/nix/store/fhaj6gmwns62s6ypkcldbaj2ybvkhx3p-foo","","")],[("/nix/store/ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv",["out"])],[],":",":",[],[("bar","/nix/store/mp57d33657rf34lzvlbpfa1gjfv5gmpg-bar"),("builder",":"),("name","foo"),("out","/nix/store/fhaj6gmwns62s6ypkcldbaj2ybvkhx3p-foo"),("system",":")])
\ No newline at end of file
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv.json b/tvix/nix-compat/src/derivation/tests/derivation_tests/ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv.json
new file mode 100644
index 000000000000..831d27956d86
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv.json
@@ -0,0 +1,23 @@
+{
+  "args": [],
+  "builder": ":",
+  "env": {
+    "bar": "/nix/store/mp57d33657rf34lzvlbpfa1gjfv5gmpg-bar",
+    "builder": ":",
+    "name": "foo",
+    "out": "/nix/store/fhaj6gmwns62s6ypkcldbaj2ybvkhx3p-foo",
+    "system": ":"
+  },
+  "inputDrvs": {
+    "/nix/store/ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv": [
+      "out"
+    ]
+  },
+  "inputSrcs": [],
+  "outputs": {
+    "out": {
+      "path": "/nix/store/fhaj6gmwns62s6ypkcldbaj2ybvkhx3p-foo"
+    }
+  },
+  "system": ":"
+}
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/h32dahq0bx5rp1krcdx3a53asj21jvhk-has-multi-out.drv b/tvix/nix-compat/src/derivation/tests/derivation_tests/h32dahq0bx5rp1krcdx3a53asj21jvhk-has-multi-out.drv
new file mode 100644
index 000000000000..523612238c76
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/h32dahq0bx5rp1krcdx3a53asj21jvhk-has-multi-out.drv
@@ -0,0 +1 @@
+Derive([("lib","/nix/store/2vixb94v0hy2xc6p7mbnxxcyc095yyia-has-multi-out-lib","",""),("out","/nix/store/55lwldka5nyxa08wnvlizyqw02ihy8ic-has-multi-out","","")],[],[],":",":",[],[("builder",":"),("lib","/nix/store/2vixb94v0hy2xc6p7mbnxxcyc095yyia-has-multi-out-lib"),("name","has-multi-out"),("out","/nix/store/55lwldka5nyxa08wnvlizyqw02ihy8ic-has-multi-out"),("outputs","out lib"),("system",":")])
\ No newline at end of file
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/h32dahq0bx5rp1krcdx3a53asj21jvhk-has-multi-out.drv.json b/tvix/nix-compat/src/derivation/tests/derivation_tests/h32dahq0bx5rp1krcdx3a53asj21jvhk-has-multi-out.drv.json
new file mode 100644
index 000000000000..0bd7a2991cc7
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/h32dahq0bx5rp1krcdx3a53asj21jvhk-has-multi-out.drv.json
@@ -0,0 +1,23 @@
+{
+  "args": [],
+  "builder": ":",
+  "env": {
+    "builder": ":",
+    "lib": "/nix/store/2vixb94v0hy2xc6p7mbnxxcyc095yyia-has-multi-out-lib",
+    "name": "has-multi-out",
+    "out": "/nix/store/55lwldka5nyxa08wnvlizyqw02ihy8ic-has-multi-out",
+    "outputs": "out lib",
+    "system": ":"
+  },
+  "inputDrvs": {},
+  "inputSrcs": [],
+  "outputs": {
+    "lib": {
+      "path": "/nix/store/2vixb94v0hy2xc6p7mbnxxcyc095yyia-has-multi-out-lib"
+    },
+    "out": {
+      "path": "/nix/store/55lwldka5nyxa08wnvlizyqw02ihy8ic-has-multi-out"
+    }
+  },
+  "system": ":"
+}
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv b/tvix/nix-compat/src/derivation/tests/derivation_tests/ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv
new file mode 100644
index 000000000000..559e93ed0ed6
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv
@@ -0,0 +1 @@
+Derive([("out","/nix/store/mp57d33657rf34lzvlbpfa1gjfv5gmpg-bar","r:sha1","0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33")],[],[],":",":",[],[("builder",":"),("name","bar"),("out","/nix/store/mp57d33657rf34lzvlbpfa1gjfv5gmpg-bar"),("outputHash","0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33"),("outputHashAlgo","sha1"),("outputHashMode","recursive"),("system",":")])
\ No newline at end of file
diff --git a/tvix/nix-compat/src/derivation/tests/derivation_tests/ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv.json b/tvix/nix-compat/src/derivation/tests/derivation_tests/ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv.json
new file mode 100644
index 000000000000..e297d271592f
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/derivation_tests/ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv.json
@@ -0,0 +1,23 @@
+{
+  "args": [],
+  "builder": ":",
+  "env": {
+    "builder": ":",
+    "name": "bar",
+    "out": "/nix/store/mp57d33657rf34lzvlbpfa1gjfv5gmpg-bar",
+    "outputHash": "0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33",
+    "outputHashAlgo": "sha1",
+    "outputHashMode": "recursive",
+    "system": ":"
+  },
+  "inputDrvs": {},
+  "inputSrcs": [],
+  "outputs": {
+    "out": {
+      "hash": "0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33",
+      "hashAlgo": "r:sha1",
+      "path": "/nix/store/mp57d33657rf34lzvlbpfa1gjfv5gmpg-bar"
+    }
+  },
+  "system": ":"
+}
diff --git a/tvix/nix-compat/src/derivation/tests/mod.rs b/tvix/nix-compat/src/derivation/tests/mod.rs
new file mode 100644
index 000000000000..57c08f5a75f3
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/tests/mod.rs
@@ -0,0 +1,344 @@
+use crate::derivation::output::{Hash, Output};
+use crate::derivation::Derivation;
+use crate::store_path::StorePath;
+use std::collections::BTreeSet;
+use std::fs::File;
+use std::io::Read;
+use std::path::Path;
+use test_case::test_case;
+use test_generator::test_resources;
+
+const RESOURCES_PATHS: &str = "src/derivation/tests/derivation_tests";
+
+fn read_file(path: &str) -> String {
+    let path = Path::new(path);
+    let mut file = File::open(path).unwrap();
+    let mut data = String::new();
+
+    file.read_to_string(&mut data).unwrap();
+
+    return data;
+}
+
+#[test_resources("src/derivation/tests/derivation_tests/*.drv")]
+fn check_serizaliation(path_to_drv_file: &str) {
+    let data = read_file(&format!("{}.json", path_to_drv_file));
+    let derivation: Derivation = serde_json::from_str(&data).expect("JSON was not well-formatted");
+
+    let mut serialized_derivation = String::new();
+    derivation.serialize(&mut serialized_derivation).unwrap();
+
+    let expected = read_file(path_to_drv_file);
+
+    assert_eq!(expected, serialized_derivation);
+}
+
+#[test_resources("src/derivation/tests/derivation_tests/*.drv")]
+fn validate(path_to_drv_file: &str) {
+    let data = read_file(&format!("{}.json", path_to_drv_file));
+    let derivation: Derivation = serde_json::from_str(&data).expect("JSON was not well-formatted");
+
+    derivation
+        .validate(true)
+        .expect("derivation failed to validate")
+}
+
+#[test_resources("src/derivation/tests/derivation_tests/*.drv")]
+fn check_to_string(path_to_drv_file: &str) {
+    let data = read_file(&format!("{}.json", path_to_drv_file));
+    let derivation: Derivation = serde_json::from_str(&data).expect("JSON was not well-formatted");
+
+    let expected = read_file(path_to_drv_file);
+
+    assert_eq!(expected, derivation.to_string());
+}
+
+#[test_case("bar","0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv"; "fixed_sha256")]
+#[test_case("foo", "4wvvbi4jwn0prsdxb7vs673qa5h9gr7x-foo.drv"; "simple-sha256")]
+#[test_case("bar", "ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv"; "fixed-sha1")]
+#[test_case("foo", "ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv"; "simple-sha1")]
+#[test_case("has-multi-out", "h32dahq0bx5rp1krcdx3a53asj21jvhk-has-multi-out.drv"; "multiple-outputs")]
+#[test_case("structured-attrs", "9lj1lkjm2ag622mh4h9rpy6j607an8g2-structured-attrs.drv"; "structured-attrs")]
+#[test_case("unicode", "52a9id8hx688hvlnz4d1n25ml1jdykz0-unicode.drv"; "unicode")]
+fn derivation_path(name: &str, expected_path: &str) {
+    let data = read_file(&format!("{}/{}.json", RESOURCES_PATHS, expected_path));
+    let derivation: Derivation = serde_json::from_str(&data).expect("JSON was not well-formatted");
+
+    assert_eq!(
+        derivation.calculate_derivation_path(name).unwrap(),
+        StorePath::from_string(expected_path).unwrap()
+    );
+}
+
+/// This trims all outputs from a Derivation struct,
+/// by setting outputs[$outputName].path and environment[$outputName] to the empty string.
+fn derivation_with_trimmed_outputs(derivation: &Derivation) -> Derivation {
+    let mut trimmed_env = derivation.environment.clone();
+    let mut trimmed_outputs = derivation.outputs.clone();
+
+    for (output_name, output) in &derivation.outputs {
+        trimmed_env.insert(output_name.clone(), "".to_string());
+        assert!(trimmed_outputs.contains_key(output_name));
+        trimmed_outputs.insert(
+            output_name.to_string(),
+            Output {
+                path: "".to_string(),
+                ..output.clone()
+            },
+        );
+    }
+
+    // replace environment and outputs with the trimmed variants
+    Derivation {
+        environment: trimmed_env,
+        outputs: trimmed_outputs,
+        ..derivation.clone()
+    }
+}
+
+#[test_case("0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv", "724f3e3634fce4cbbbd3483287b8798588e80280660b9a63fd13a1bc90485b33"; "fixed_sha256")]
+#[test_case("ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv", "c79aebd0ce3269393d4a1fde2cbd1d975d879b40f0bf40a48f550edc107fd5df";"fixed-sha1")]
+fn replacement_drv_path(drv_path: &str, expected_replacement_str: &str) {
+    // read in the fixture
+    let data = read_file(&format!("{}/{}.json", RESOURCES_PATHS, drv_path));
+    let drv: Derivation = serde_json::from_str(&data).expect("must deserialize");
+
+    let drv_replacement_str = drv.calculate_drv_replacement_str(|_| panic!("must not be called"));
+
+    assert_eq!(expected_replacement_str, drv_replacement_str);
+}
+
+#[test_case("bar","0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv"; "fixed_sha256")]
+#[test_case("foo", "4wvvbi4jwn0prsdxb7vs673qa5h9gr7x-foo.drv"; "simple-sha256")]
+#[test_case("bar", "ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv"; "fixed-sha1")]
+#[test_case("foo", "ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv"; "simple-sha1")]
+#[test_case("has-multi-out", "h32dahq0bx5rp1krcdx3a53asj21jvhk-has-multi-out.drv"; "multiple-outputs")]
+#[test_case("structured-attrs", "9lj1lkjm2ag622mh4h9rpy6j607an8g2-structured-attrs.drv"; "structured-attrs")]
+#[test_case("unicode", "52a9id8hx688hvlnz4d1n25ml1jdykz0-unicode.drv"; "unicode")]
+fn output_paths(name: &str, drv_path: &str) {
+    // read in the fixture
+    let data = read_file(&format!("{}/{}.json", RESOURCES_PATHS, drv_path));
+    let expected_derivation: Derivation = serde_json::from_str(&data).expect("must deserialize");
+
+    let mut derivation = derivation_with_trimmed_outputs(&expected_derivation);
+
+    // calculate the drv replacement string.
+    // We don't expect the lookup function to be called for most derivations.
+    let replacement_str = derivation.calculate_drv_replacement_str(|drv_name| {
+        // 4wvvbi4jwn0prsdxb7vs673qa5h9gr7x-foo.drv may lookup /nix/store/0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv
+        // ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv may lookup /nix/store/ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv
+        if name == "foo"
+            && ((drv_path == "4wvvbi4jwn0prsdxb7vs673qa5h9gr7x-foo.drv"
+                && drv_name == "/nix/store/0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv")
+                || (drv_path == "ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv"
+                    && drv_name == "/nix/store/ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv"))
+        {
+            // do the lookup, by reading in the fixture of the requested
+            // drv_name, and calculating its drv replacement (on the non-stripped version)
+            // In a real-world scenario you would have already done this during construction.
+
+            let data = read_file(&format!(
+                "{}/{}.json",
+                RESOURCES_PATHS,
+                Path::new(drv_name).file_name().unwrap().to_string_lossy()
+            ));
+
+            let drv: Derivation = serde_json::from_str(&data).expect("must deserialize");
+
+            // calculate replacement string. These don't trigger any subsequent requests, as they're both FOD.
+            drv.calculate_drv_replacement_str(|_| panic!("must not lookup"))
+        } else {
+            // we only expect this to be called in the "foo" testcase, for the "bar derivations"
+            panic!("may only be called for foo testcase on bar derivations");
+        }
+    });
+
+    // We need to calculate the replacement_str, as fixed-sha1 does use it.
+    derivation
+        .calculate_output_paths(&name, &replacement_str)
+        .unwrap();
+
+    // The derivation should now look like it was before
+    assert_eq!(expected_derivation, derivation);
+}
+
+/// Exercises the output path calculation functions like a constructing client
+/// (an implementation of builtins.derivation) would do:
+///
+/// ```nix
+/// rec {
+///   bar = builtins.derivation {
+///     name = "bar";
+///     builder = ":";
+///     system = ":";
+///     outputHash = "08813cbee9903c62be4c5027726a418a300da4500b2d369d3af9286f4815ceba";
+///     outputHashAlgo = "sha256";
+///     outputHashMode = "recursive";
+///   };
+///
+///   foo = builtins.derivation {
+///     name = "foo";
+///     builder = ":";
+///     system = ":";
+///     inherit bar;
+///   };
+/// }
+/// ```
+/// It first assembles the bar derivation, does the output path calculation on
+/// it, then continues with the foo derivation.
+///
+/// The code ensures the resulting Derivations match our fixtures.
+#[test]
+fn output_path_construction() {
+    // create the bar derivation
+    let mut bar_drv = Derivation {
+        builder: ":".to_string(),
+        system: ":".to_string(),
+        ..Default::default()
+    };
+
+    // assemble bar env
+    let bar_env = &mut bar_drv.environment;
+    bar_env.insert("builder".to_string(), ":".to_string());
+    bar_env.insert("name".to_string(), "bar".to_string());
+    bar_env.insert("out".to_string(), "".to_string()); // will be calculated
+    bar_env.insert(
+        "outputHash".to_string(),
+        "08813cbee9903c62be4c5027726a418a300da4500b2d369d3af9286f4815ceba".to_string(),
+    );
+    bar_env.insert("outputHashAlgo".to_string(), "sha256".to_string());
+    bar_env.insert("outputHashMode".to_string(), "recursive".to_string());
+    bar_env.insert("system".to_string(), ":".to_string());
+
+    // assemble bar outputs
+    bar_drv.outputs.insert(
+        "out".to_string(),
+        Output {
+            path: "".to_string(), // will be calculated
+            hash: Some(Hash {
+                digest: "08813cbee9903c62be4c5027726a418a300da4500b2d369d3af9286f4815ceba"
+                    .to_string(),
+                algo: "r:sha256".to_string(),
+            }),
+        },
+    );
+
+    // calculate bar output paths
+    let bar_calc_result = bar_drv.calculate_output_paths(
+        "bar",
+        &bar_drv.calculate_drv_replacement_str(|_| panic!("is FOD, should not lookup")),
+    );
+    assert!(bar_calc_result.is_ok());
+
+    // ensure it matches our bar fixture
+    let bar_data = read_file(&format!(
+        "{}/{}.json",
+        RESOURCES_PATHS, "0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv"
+    ));
+    let bar_drv_expected: Derivation = serde_json::from_str(&bar_data).expect("must deserialize");
+    assert_eq!(bar_drv_expected, bar_drv);
+
+    // now construct foo, which requires bar_drv
+    // Note how we refer to the output path, drv name and replacement_str (with calculated output paths) of bar.
+    let bar_output_path = &bar_drv.outputs.get("out").expect("must exist").path;
+    let bar_drv_replacement_str =
+        &bar_drv.calculate_drv_replacement_str(|_| panic!("is FOD, should not lookup"));
+
+    let bar_drv_path = bar_drv
+        .calculate_derivation_path("bar")
+        .expect("must succeed");
+
+    // create foo derivation
+    let mut foo_drv = Derivation {
+        builder: ":".to_string(),
+        system: ":".to_string(),
+        ..Default::default()
+    };
+
+    // assemble foo env
+    let foo_env = &mut foo_drv.environment;
+    foo_env.insert("bar".to_string(), bar_output_path.to_string());
+    foo_env.insert("builder".to_string(), ":".to_string());
+    foo_env.insert("name".to_string(), "foo".to_string());
+    foo_env.insert("out".to_string(), "".to_string()); // will be calculated
+    foo_env.insert("system".to_string(), ":".to_string());
+
+    // asssemble foo outputs
+    foo_drv.outputs.insert(
+        "out".to_string(),
+        Output {
+            path: "".to_string(), // will be calculated
+            hash: None,
+        },
+    );
+
+    // assemble foo input_derivations
+    foo_drv.input_derivations.insert(
+        bar_drv_path.to_absolute_path(),
+        BTreeSet::from(["out".to_string()]),
+    );
+
+    // calculate foo output paths
+    let foo_calc_result = foo_drv.calculate_output_paths(
+        "foo",
+        &foo_drv.calculate_drv_replacement_str(|drv_name| {
+            if drv_name != "/nix/store/0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv" {
+                panic!("lookup called with unexpected drv_name: {}", drv_name);
+            }
+            bar_drv_replacement_str.clone()
+        }),
+    );
+    assert!(foo_calc_result.is_ok());
+
+    // ensure it matches our foo fixture
+    let foo_data = read_file(&format!(
+        "{}/{}.json",
+        RESOURCES_PATHS, "4wvvbi4jwn0prsdxb7vs673qa5h9gr7x-foo.drv",
+    ));
+    let foo_drv_expected: Derivation = serde_json::from_str(&foo_data).expect("must deserialize");
+    assert_eq!(foo_drv_expected, foo_drv);
+
+    assert_eq!(
+        StorePath::from_string("4wvvbi4jwn0prsdxb7vs673qa5h9gr7x-foo.drv").expect("must succeed"),
+        foo_drv
+            .calculate_derivation_path("foo")
+            .expect("must succeed")
+    );
+}
+
+#[test]
+fn path_with_zero_references() {
+    // This hash should match `builtins.toFile`, e.g.:
+    //
+    // nix-repl> builtins.toFile "foo" "bar"
+    // "/nix/store/vxjiwkjkn7x4079qvh1jkl5pn05j2aw0-foo"
+
+    let store_path = crate::derivation::path_with_references("foo", "bar", Vec::<String>::new())
+        .expect("path_with_references() should succeed");
+
+    assert_eq!(
+        store_path.to_absolute_path().as_str(),
+        "/nix/store/vxjiwkjkn7x4079qvh1jkl5pn05j2aw0-foo"
+    );
+}
+
+#[test]
+fn path_with_non_zero_references() {
+    // This hash should match:
+    //
+    // nix-repl> builtins.toFile "baz" "${builtins.toFile "foo" "bar"}"
+    // "/nix/store/5xd714cbfnkz02h2vbsj4fm03x3f15nf-baz"
+
+    let inner = crate::derivation::path_with_references("foo", "bar", Vec::<String>::new())
+        .expect("path_with_references() should succeed");
+    let inner_path = inner.to_absolute_path();
+
+    let outer =
+        crate::derivation::path_with_references("baz", &inner_path, vec![inner_path.as_str()])
+            .expect("path_with_references() should succeed");
+
+    assert_eq!(
+        outer.to_absolute_path().as_str(),
+        "/nix/store/5xd714cbfnkz02h2vbsj4fm03x3f15nf-baz"
+    );
+}