fetchMavenArtifact: init (#16825)

fetchMavenArtifact downloads a Maven artifact given a group id, an artifact id,
and a version.

Example usage:

   org_apache_httpcomponents_httpclient_4_5_2 = fetchMavenArtifact {
     groupId = "org.apache.httpcomponents";
     artifactId = "httpclient";
     version = "4.5.2";
     sha256 = "0ms00zc28pwqk83nwwbafhq6p8zci9mrjzbqalpn6v0d80hwdzqd";
     # Optionally: repos = [ ... urls to some Maven repos to use ... ];
     # Optionally: url, urls - pointing directly to a specific jar url.
   };

Now `org_apache_httpcomponents_httpclient_4_5_2.jar` points to the downloaded
JAR file, while `org_apache_httpcomponents_httpclient_4_5_2` refers to a
derivation that when used used in `buildInputs` will be automatically added to
the Java classpath.

pkgs/build-support/fetchmavenartifact/default.nix

@@ -0,0 +1,75 @@
+# Adaptation of the MIT-licensed work on `sbt2nix` done by Charles O'Farrell
+
+{ fetchurl, stdenv }:
+let
+  defaultRepos = [
+    http://central.maven.org/maven2
+    http://oss.sonatype.org/content/repositories/releases
+    http://oss.sonatype.org/content/repositories/public
+    http://repo.typesafe.com/typesafe/releases
+  ];
+in
+
+args@
+{ # Example: "org.apache.httpcomponents"
+  groupId
+, # Example: "httpclient"
+  artifactId
+, # Example: "4.3.6"
+  version
+, # List of maven repositories from where to fetch the artifact.
+  # Example: [ http://oss.sonatype.org/content/repositories/public ].
+  repos ? defaultRepos
+  # The `url` and `urls` parameters, if specified should point to the JAR
+  # file and will take precedence over the `repos` parameter. Only one of `url`
+  # and `urls` can be specified, not both.
+, url ? ""
+, urls ? []
+, # The rest of the arguments are just forwarded to `fetchurl`.
+  ...
+}:
+
+# only one of url and urls can be specified at a time.
+assert (url == "") || (urls == []);
+# if repos is empty, then url or urls must be specified.
+assert (repos != []) || (url != "") || (urls != []);
+
+
+let
+  name_ =
+    with stdenv.lib; concatStrings [
+      (replaceChars ["."] ["_"] groupId) "_"
+      (replaceChars ["."] ["_"] artifactId) "-"
+      version
+    ];
+  mkJarUrl = repoUrl:
+    with stdenv.lib; concatStringsSep "/" [
+      (removeSuffix "/" repoUrl)
+      (replaceChars ["."] ["/"] groupId)
+      artifactId
+      version
+      "${artifactId}-${version}.jar"
+    ];
+  urls_ =
+    if url != "" then [url]
+    else if urls != [] then urls
+    else map mkJarUrl repos;
+  jar =
+    fetchurl (
+      builtins.removeAttrs args ["groupId" "artifactId" "version" "repos" "url" ]
+        // { urls = urls_; name = "${name_}.jar"; }
+    );
+in
+  stdenv.mkDerivation {
+    name = name_;
+    phases = "installPhase fixupPhase";
+    # By moving the jar to $out/share/java we make it discoverable by java
+    # packages packages that mention this derivation in their buildInputs.
+    installPhase = ''
+      mkdir -p $out/share/java
+      ln -s ${jar} $out/share/java
+    '';
+    # We also add a `jar` attribute that can be used to easily obtain the path
+    # to the downloaded jar file.
+    passthru.jar = jar;
+  }

pkgs/top-level/all-packages.nix

@@ -167,6 +167,8 @@ in
 
   fetchmtn = callPackage ../build-support/fetchmtn (config.fetchmtn or {});
 
+  fetchMavenArtifact = callPackage ../build-support/fetchmavenartifact { };
+
   packer = callPackage ../development/tools/packer { };
 
   fetchpatch = callPackage ../build-support/fetchpatch { };