Add extraInit and buildJdk args

gradle-env.nix

@@ -21,23 +21,33 @@
 
 { stdenv, buildEnv, fetchurl, gradleGen, writeText, writeTextDir }:
 
-{ envSpec
+{
+# Path to the environment spec generated by gradle2nix (e.g. gradle-env.json).
+  envSpec
 , pname ? null
 , version ? null
 , enableParallelBuilding ? true
+# Arguments to Gradle used to build the project in buildPhase.
 , gradleFlags ? [ "build" ]
+# Gradle package to use instead of the one generated by gradle2nix.
 , gradlePackage ? null
+# Enable debugging for the Gradle build; this will cause Gradle to run a debug server
+# and wait for a JVM debugging client to attach.
 , enableDebug ? false
+# Additional code to run in the Gradle init script (init.gradle).
+, extraInit ? ""
+# Override the default JDK used to run Gradle itself.
+, buildJdk ? null
 , ... } @ args:
 
 let
   inherit (builtins)
-    filter sort replaceStrings attrValues match fromJSON
-    concatStringsSep;
+    attrValues concatStringsSep filter fromJSON match replaceStrings sort;
 
   inherit (stdenv.lib)
-    versionOlder unique mapAttrs mapAttrsToList last concatMapStringsSep
-    removeSuffix optionalString groupBy' readFile hasSuffix;
+    assertMsg concatMapStringsSep groupBy' hasSuffix last mapAttrs
+    mapAttrsToList optionalString readFile removeSuffix unique versionAtLeast
+    versionOlder;
 
   mkDep = depSpec: stdenv.mkDerivation {
     inherit (depSpec) name;
@@ -176,10 +186,20 @@ let
     paths = map mkDep deps ++ mkModuleMetadata deps ++ mkSnapshotMetadata deps;
   };
 
-  mkInitScript = projectSpec:
+  mkInitScript = projectSpec: gradle:
     let
       repos = mapAttrs (mkRepo projectSpec.name) projectSpec.dependencies;
+      hasDependencies = mapAttrs (type: deps: deps != []) projectSpec.dependencies;
     in
+      assert (assertMsg (hasDependencies.settings -> versionAtLeast gradle.version "6.0") ''
+        Project `${projectSpec.name}' has settings script dependencies, such as settings
+        plugins, which are not supported by gradle2nix for Gradle versions prior to 6.0.
+
+        Potential remedies:
+        - Pass `--gradle-version=<version>' to the gradle2nix command.
+        - Patch the `settings.gradle[.kts]' file to remove script dependencies.
+      '');
+
       writeText "init.gradle" ''
         static def offlineRepo(RepositoryHandler repositories, String env, String path) {
             repositories.clear()
@@ -204,18 +224,37 @@ let
             }
         }
 
-        gradle.settingsEvaluated {
-            offlineRepo(it.pluginManagement.repositories, "plugin", "${repos.plugin}")
-        }
+        ${optionalString (hasDependencies.settings && (versionAtLeast gradle.version "6.0")) ''
+          gradle.beforeSettings {
+              offlineRepo(it.buildscript.repositories, "settings", "${repos.settings}")
+          }
+        ''}
 
-        gradle.projectsLoaded {
-            allprojects {
-                buildscript {
-                    offlineRepo(repositories, "buildscript", "${repos.buildscript}")
-                }
-                offlineRepo(repositories, "project", "${repos.project}")
-            }
-        }
+        ${optionalString (hasDependencies.plugin) ''
+          gradle.settingsEvaluated {
+              offlineRepo(it.pluginManagement.repositories, "plugin", "${repos.plugin}")
+          }
+        ''}
+
+        ${optionalString (hasDependencies.buildscript) ''
+          gradle.projectsLoaded {
+              allprojects {
+                  buildscript {
+                      offlineRepo(repositories, "buildscript", "${repos.buildscript}")
+                  }
+              }
+          }
+        ''}
+
+        ${optionalString (hasDependencies.project) ''
+          gradle.projectsLoaded {
+              allprojects {
+                  offlineRepo(repositories, "project", "${repos.project}")
+              }
+          }
+        ''}
+
+        ${extraInit}
       '';
 
   mkGradle = gradleSpec:
@@ -227,12 +266,14 @@ let
       src = fetchurl {
         inherit (gradleSpec) url sha256;
       };
+    } // {
+      inherit (gradleSpec) version;
     };
 
-  mkProjectEnv = projectSpec: {
+  mkProjectEnv = projectSpec: rec {
     inherit (projectSpec) name path version;
-    initScript = mkInitScript projectSpec;
     gradle = args.gradlePackage or mkGradle projectSpec.gradle;
+    initScript = mkInitScript projectSpec gradle;
   };
 
   gradleEnv = mapAttrs
@@ -248,6 +289,7 @@ let
       --info --full-stacktrace --warning-mode=all \
       ${optionalString enableParallelBuilding "--parallel"} \
       ${optionalString enableDebug "-Dorg.gradle.debug=true"} \
+      ${optionalString (buildJdk != null) "-Dorg.gradle.java.home=${buildJdk.home}"} \
       --init-script ${env.initScript} \
       ${optionalString (env.path != "") ''-p "${env.path}"''} \
       ${concatStringsSep " " flags}
@@ -270,7 +312,7 @@ in stdenv.mkDerivation (args // {
     runHook preBuild
 
     (
-    set -x
+    set -eux
 
     # use the init script here
     TMPHOME=$(mktemp -d)