php: add packagist translator

docs/src/subsystems/php.md

@@ -26,6 +26,12 @@ Resolves dependencies in `composer.json` using `composer` to generate a
 `composer.lock` lockfile, then invokes the `composer-lock` translator to
 generate a dream2nix lockfile.
 
+### packagist (impure)
+
+Downloads a package version from [Packagist](https://packagist.org/).
+Then uses `composer-lock` if a `composer.lock` file is present,
+or `composer-json` otherwise to translate the package.
+
 ## Builders
 
 ### granular (pure) (default)

src/subsystems/php/translators/packagist/default.nix

@@ -0,0 +1,97 @@
+{
+  dlib,
+  lib,
+  ...
+}: {
+  type = "impure";
+
+  # the input format is specified in /specifications/translator-call-example.json
+  # this script receives a json file including the input paths and specialArgs
+  translateBin = {
+    # dream2nix utils
+    apps,
+    subsystems,
+    utils,
+    # nixpkgs dependenies
+    coreutils,
+    curl,
+    jq,
+    git,
+    moreutils,
+    ...
+  }:
+    utils.writePureShellScript
+    [
+      coreutils
+      curl
+      jq
+      git
+      moreutils
+    ]
+    ''
+      # according to the spec, the translator reads the input from a json file
+      jsonInput=$1
+
+      # read the json input
+      outputFile=$(realpath -m $(jq '.outputFile' -c -r $jsonInput))
+      name=$(jq '.project.name' -c -r $jsonInput)
+      version=$(jq '.project.version' -c -r $jsonInput)
+
+      pushd $TMPDIR
+
+      # download and unpack package source
+      curl https://packagist.org/packages/$name.json | \
+        jq -rcM ".package.versions.\"$version\".source" \
+        > source_manifest
+      SOURCE_URL=$(jq -rcM ".url" source_manifest)
+      SOURCE_REV=$(jq -rcM ".reference" source_manifest)
+
+      mkdir source
+      pushd source
+      git init
+      git remote add origin $SOURCE_URL
+      git fetch --depth 1 origin $SOURCE_REV
+      git checkout FETCH_HEAD
+      popd
+
+      # generate arguments for package-lock translator
+      echo "{
+        \"source\": \"$TMPDIR/source\",
+        \"outputFile\": \"$outputFile\",
+        \"project\": {
+          \"name\": \"$name\",
+          \"relPath\": \"\"
+        }
+      }" > $TMPDIR/newJsonInput
+
+      popd
+
+      if [ -e $TMPDIR/source/composer.lock ]
+      then
+        ${subsystems.php.translators.composer-lock.translateBin} $TMPDIR/newJsonInput
+      else
+        ${subsystems.php.translators.composer-json.translateBin} $TMPDIR/newJsonInput
+      fi
+
+      # add main package source info to dream-lock.json
+      echo "
+        {
+          \"type\": \"git\",
+          \"url\": \"$SOURCE_URL\",
+          \"rev\": \"$SOURCE_REV\"
+        }
+      " > $TMPDIR/sourceInfo.json
+
+      ${apps.callNixWithD2N} eval --json "
+        with dream2nix.utils.dreamLock;
+        replaceRootSources {
+          dreamLock = l.fromJSON (l.readFile \"$outputFile\");
+          newSourceRoot = l.fromJSON (l.readFile \"$TMPDIR/sourceInfo.json\");
+        }
+      " \
+        | sponge "$outputFile"
+    '';
+
+  # inherit options from composer-json translator
+  extraArgs = dlib.translators.translators.php.composer-json.extraArgs;
+}