nix: add docs about NodeJS modules, small refactor

Signed-off-by: Jakub Sokołowski <jakub@status.im>

nix/deps/nodejs-patched/README.md

@@ -0,0 +1,18 @@
+# Description
+
+This Nix derivation takes the result of the [`nix/deps/nodejs/default.nix`](../nodejs/default.nix) derivation and adjusts it for use with Gradle.
+
+# Details
+
+Modules provided by `yarn2nix` are normally fine, but we use `react-native-*` packages which have their own `gradle.build` files that reference external Maven repositories:
+```js
+repositories {
+    google()
+    jcenter()
+}
+```
+And these need to be patched and replaced with `mavenLocal()` to make sure Gradle doesn't try to fetch dependencies from remote repos.
+
+This derivation symlinks most of the modules found in the `yarn2nix` result and copies the ones that require patching of `gradle.build` files in `patchGradlePhase`.
+
+It also applies other fixes like making `BuildId` static in `patchBuildIdPhase` and fixing a Hermes bug in `patchHermesPhase`.

nix/deps/nodejs-patched/default.nix

@@ -6,8 +6,14 @@
 
 stdenv.mkDerivation {
   name = "${deps.nodejs.name}-patched";
-
+  phases = [
-  phases = [ "unpackPhase" "patchPhase" "installPhase" ];
+    "unpackPhase"
+    "patchGradlePhase"
+    "patchBuildIdPhase"
+    "patchHermesPhase"
+    "patchJavaPhase"
+    "installPhase"
+  ];
 
   # First symlink all modules as is
   # WARNING: Metro has issues when dealing with symlinks!
@@ -19,10 +25,10 @@ stdenv.mkDerivation {
     cp -r ${deps.nodejs}/node_modules/.bin ./node_modules/
   '';
 
-  # Then patch the modules that have build.gradle files
+  # Patch build.gradle files in 'react-native-*' dependencies to replace
-  patchPhase = ''
+  # maven and google central repositories with our own local directories.
-    # Patch maven and google central repositories with our own local directories.
+  # This prevents the builder from downloading Maven artifacts
-    # This prevents the builder from downloading Maven artifacts
+  patchGradlePhase = ''
     for modBuildGradle in $(find -L ./node_modules -name build.gradle); do
       relativeToNode=''${modBuildGradle#*node_modules/}
       moduleName=''${relativeToNode%%/*}
@@ -33,26 +39,26 @@ stdenv.mkDerivation {
       fi
       ${patchMavenSources} $modBuildGradle
     done
-
+  '';
-    patchShebangs ./node_modules
+  # Do not add a BuildId to the generated libraries, for reproducibility
-
+  patchBuildIdPhase = ''
-    # Do not add a BuildId to the generated libraries, for reproducibility
     substituteInPlace ./node_modules/react-native/ReactAndroid/src/main/jni/Application.mk --replace \
         '-Wl,--build-id' \
         '-Wl,--build-id=none'
-
+  '';
-    # Fix bugs in Hermes usage:
+  # Fix bugs in Hermes usage:
-    # https://github.com/facebook/react-native/issues/25601#issuecomment-510856047
+  # https://github.com/facebook/react-native/issues/25601#issuecomment-510856047
-    # - Make PR builds also count as release builds
+  # - Make PR builds also count as release builds
-    # - Fix issue where hermes command is being called with same input/output file
+  # - Fix issue where hermes command is being called with same input/output file
+  patchHermesPhase = ''
     substituteInPlace ./node_modules/react-native/react.gradle --replace \
         'targetName.toLowerCase().contains("release")' \
         '!targetName.toLowerCase().contains("debug")'
-
+  '';
-    # Patch Java files in modules which are not yet ported to AndroidX
+  # Patch Java files in modules which are not yet ported to AndroidX
+  patchJavaPhase = ''
     ${nodejs}/bin/node ./node_modules/jetifier/bin/jetify
   '';
-
   installPhase = ''
     mkdir -p $out
     cp -R node_modules $out/

nix/deps/nodejs/README.md

@@ -0,0 +1,58 @@
+# Description
+
+This derivation uses a [yarn2nix](https://github.com/nix-community/yarn2nix) to generate a Nix store package containing all NodeJS dependencies.
+
+# Details
+
+If you look at [`nix/deps/nodejs/default.nix`](./default.nix) you'll see that it it loads `package.json` and `yarn.lock` files and uses them to generate the derivation:
+```sh
+ > make nix-repl
+Welcome to Nix version 2.3.9. Type :? for help.
+
+nix-repl> pkgs.deps.nodejs
+«derivation /nix/store/23mpmpjjnq7miclv6bc6ilgypy8wz69p-status-react-node-deps-1.8.0.drv»
+```
+You can build the derivation:
+```
+nix-repl> :b pkgs.deps.nodejs    
+
+this derivation produced the following outputs:
+  out -> /nix/store/dqb2cjyz1g6n7jic07058y26lnmgaaz9-status-react-node-deps-1.8.0
+```
+And look inside:
+```
+ > cd /nix/store/dqb2cjyz1g6n7jic07058y26lnmgaaz9-status-react-node-deps-1.8.0
+ > ls
+deps  node_modules
+ > ls node_modules | grep react-native-image
+react-native-image-crop-picker
+react-native-image-resizer
+react-native-image-viewing
+```
+
+# Known Issues
+
+It's important that dependencies from GitHub are added in a correct format:
+```
+git+https://github.com/status-im/bignumber.js.git#v4.0.2-status
+```
+Notice three things:
+
+* `git+` prefix for the `https://` URL
+* Repository name ends with `.git`
+* Tag or branch is added after `#` character
+
+__WARNING__: Using branches can cause dependencies to change their hash and cause builds to fail. Using them during development is fine, but tags should be used in the final version.
+
+If this format is not used correctly you can see issues like:
+```
+fatal: unable to access 'https://github.com/status-im/bignumber.js.git/': Could not resolve host: github.com
+```
+or
+```
+error Couldn't find any versions for "bignumber.js" that matches "github.com/status-im/bignumber.js.git#v4.0.2-status" in our cache (possible versions are ""). This is usually caused by a missing entry in the lockfile, running Yarn without the --offline flag may help fix this issue.
+```
+or
+```
+error Can't make a request in offline mode ("https://codeload.github.com/status-im/bignumber.js/tar.gz/f322b670969512a35c84441036a0ba4836a96428")
+```

nix/deps/nodejs/default.nix

@@ -1,14 +1,10 @@
 { lib, yarn2nix-moretea }:
 
-let
+# Create a yarn package for our project that contains all the dependecies.
+yarn2nix-moretea.mkYarnModules rec {
+  pname = "status-react";
+  name = "${pname}-node-deps-${version}";
   version = lib.fileContents ../../../VERSION;
   yarnLock = ../../../yarn.lock;
   packageJSON = ../../../package.json;
-  packageJSONContent = lib.importJSON packageJSON;
+}
-in
-  # Create a yarn package for our project that contains all the dependecies.
-  yarn2nix-moretea.mkYarnModules rec {
-    pname = "status-react";
-    name = "${pname}-node-deps-${version}";
-    inherit version packageJSON yarnLock;
-  }