From 6f3445b55ec849406dfb2c3a789ff8195611f753 Mon Sep 17 00:00:00 2001
From: Ivan Petkov <ivanppetkov@gmail.com>
Date: Fri, 29 Nov 2024 10:48:09 -0800
Subject: [PATCH] buildDepsOnly: prefer `dummySrc` when specified for fallback
 values (#750)

---
 CHANGELOG.md          |  3 +++
 checks/default.nix    | 14 ++++++++++++++
 docs/API.md           | 11 ++++++++---
 lib/buildDepsOnly.nix | 15 +++++++++++++--
 4 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 318bab79..f9058653 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Fixed
 * `removeReferencesToVendoredSources` now deduplicates any found references to
   avoid pathological memory usage before removing them.
+* `buildDepsOnly` will calculate fallback `pname`/`version`/`cargoVendorDir`
+  attributes using `dummySrc` if it was specified (rather than attempting to use
+  `src`)
 
 ## [0.19.3] - 2024-11-18
 A republish of 0.19.2 which was incorrectly tagged.
diff --git a/checks/default.nix b/checks/default.nix
index 6d4e2fa9..b7a92bb0 100644
--- a/checks/default.nix
+++ b/checks/default.nix
@@ -260,6 +260,20 @@ in
       touch $out
     '';
 
+  customDummy = myLib.buildDepsOnly {
+    dummySrc = pkgs.stdenv.mkDerivation {
+      pname = "custom-dummy";
+      version = "0.0.0";
+      src = myLib.cleanCargoSource ./simple;
+      postInstall = ''
+        mkdir -p $out
+        cp -r . $out
+        echo 'fn main() {}' > $out/src/main.rs
+        find $out
+      '';
+    };
+  };
+
   # https://github.com/ipetkov/crane/pull/234
   nonJsonCargoBuildLog =
     let
diff --git a/docs/API.md b/docs/API.md
index 761a2d67..2adbf1fa 100644
--- a/docs/API.md
+++ b/docs/API.md
@@ -130,7 +130,8 @@ to influence its behavior.
   be consumed without network access. Directory structure should basically
   follow the output of `cargo vendor`.
   - Default value: the result of `vendorCargoDeps` after applying the arguments
-    set (with the respective default values)
+    set (with the respective default values). Note if `dummySrc` is specified,
+    it will be used as the `src` passed into `vendorCargoDeps`
 * `checkPhaseCargoCommand`: A command to run during the derivation's check
   phase. Pre and post check hooks will automatically be run.
   - Default value: `"${cargoTestCommand} ${cargoExtraArgs}"`
@@ -140,9 +141,13 @@ to influence its behavior.
   Automatically derived if not passed in
   - Default value: `mkDummySrc args.src`
 * `pname`: package name of the derivation
-  - Default value: inherited from calling `crateNameFromCargoToml`
+  - Default value: inherited from calling `crateNameFromCargoToml`. Note if
+    `dummySrc` is specified, it will be used as the `src` passed into
+    `crateNameFromCargoToml`
 * `version`: version of the derivation
-  - Default value: inherited from calling `crateNameFromCargoToml`
+  - Default value: inherited from calling `crateNameFromCargoToml`. Note if
+    `dummySrc` is specified, it will be used as the `src` passed into
+    `crateNameFromCargoToml`
 
 #### Remove attributes
 The following attributes will be removed before being lowered to
diff --git a/lib/buildDepsOnly.nix b/lib/buildDepsOnly.nix
index fecc7935..33813d1e 100644
--- a/lib/buildDepsOnly.nix
+++ b/lib/buildDepsOnly.nix
@@ -13,7 +13,6 @@
 , ...
 }@args:
 let
-  crateName = crateNameFromCargoToml args;
   cleanedArgs = builtins.removeAttrs args [
     "cargoBuildCommand"
     "cargoCheckCommand"
@@ -39,6 +38,18 @@ let
         args.dummySrc
     else
       mkDummySrc args;
+
+  # If dummySrc is define *in args*, use it as the `src` for fallback calculations,
+  # but DO NOT use the computed `dummySrc` above as that's likely to trigger IFD
+  # (in case anyone is trying to avoid that). Dummifiying the sources should preserve
+  # the name/version of the Cargo.toml, as well as the entirety of Cargo.lock,
+  # so it shouldn't matter anyway
+  argsMaybeDummySrcOverride =
+    if args ? dummySrc
+    then args // { src = args.dummySrc; }
+    else args;
+
+  crateName = crateNameFromCargoToml argsMaybeDummySrcOverride;
 in
 mkCargoDerivation (cleanedArgs // {
   inherit doCheck;
@@ -49,7 +60,7 @@ mkCargoDerivation (cleanedArgs // {
   version = args.version or crateName.version;
 
   cargoArtifacts = null;
-  cargoVendorDir = args.cargoVendorDir or (vendorCargoDeps args);
+  cargoVendorDir = args.cargoVendorDir or (vendorCargoDeps argsMaybeDummySrcOverride);
 
   env = (args.env or { }) // {
     # Export a marker variable in case any scripts or hooks want to customize