nix: minor cleanup and documentation updates

Changes:
- Simplified `default.nix` and `shell.nix`
- Moved the default shell to `nix/shell.nix`
- Dropped unnecessary merge from  `nix/shells.nix`
- Fixed `nix/lib/getConfig.nix` to return default on `null`
- Expanded `nix/DETAILS.md` with more info
- Added links to presentations in `nix/README.md`
- Fixed a few typos

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

default.nix

@@ -1,10 +1,10 @@
 # for passing build options, see nix/README.md
-{ config ? { status-im = { }; } }:
+{ config ? { } }:
 
 let
-  main = import ./nix/default.nix { inherit config; };
+  main = import ./nix { inherit config; };
 in {
   # this is where the --attr argument selects the shell or target
   inherit (main) pkgs targets shells;
-  inherit config;
+  inherit (main.pkgs) config;
 }

nix/DETAILS.md

@@ -1,30 +1,43 @@
 # Description
 
-This document descripts the layout of our Nix setup.
+This document describes the layout of our Nix setup.
 
 # Folders
 
 There are four main folders in the `nix` directory:
 
-* `nix/scripts` - Bash scripts for easier usage of Nix
+* [`nix/scripts`](./scripts) - Bash scripts for easier usage of Nix
-* `nix/pkgs` - Packages we add to or modify in `nixpkgs`
+* [`nix/pkgs`](./pkgs) - Packages we add to or modify in `nixpkgs`
-* `nix/deps` - Project dependencies managed by Nix
+* [`nix/deps`](./deps) - Project dependencies managed by Nix
-* `nix/lib` - Our tools we merge into `pkgs.lib`
+* [`nix/lib`](./lib) - Our tools we merge into `pkgs.lib`
-* `nix/tools` - Various tools used by our derivations and shells
+* [`nix/tools`](./tools) - Various tools used by our derivations and shells
-* `nix/status-go` - Derivations for building [`status-go`](https://github.com/status-im/status-go) repo
+* [`nix/status-go`](./status-go) - Derivations for building [`status-go`](https://github.com/status-im/status-go) repo
 
 # Files
 
 There are a few main files that define the whole build environment:
 
-* `nix/nix.conf` - Binary cache configuration
+* [`nix/nix.conf`](./nix.conf) - Binary cache configuration
-* `nix/default.nix` - Entrypoint for both shells and targets
+* [`nix/default.nix`](./default.nix) - Entry point for both shells and targets
-* `nix/shells.nix` - Definition of Nix shells used in builds
+* [`nix/shell.nix`](./shell.nix) - Definition of the default Nix shell
-* `nix/targets.nix` - Hierarchy of main build targets
+* [`nix/shells.nix`](./shells.nix) - Definitions of other Nix shells used in builds
-* `nix/pkgs.nix` - Definition of a custom `nixpkgs` repo
+* [`nix/targets.nix`](./targets.nix) - Hierarchy of main build targets
-* `nix/overlay.nix` - Overrides for `nixpkgs`, custom packages
+* [`nix/pkgs.nix`](./pkgs.nix) - Definition of a custom `nixpkgs` repo
+* [`nix/config.nix`](./config.nix) - Default config values for instantiating `nixpkgs`
+* [`nix/overlay.nix`](./overlay.nix) - Overrides for `nixpkgs`, custom packages
 
-The `default.nix` and `shell.nix` files at th repo root are just a gateway into the `nix` subfolder.
+The [`default.nix`](../default.nix) and [`shell.nix`](../shell.nix) files at th repo root are just a gateway into the `nix` sub folder.
+
+# Scripts
+
+There's a few scripts in [`nix/scripts`](./scripts) that make use of Nix simpler:
+
+* [`nix/scripts/setup.sh`](./scripts/setup.sh) - Installs Nix Package manager
+* [`nix/scripts/source.sh`](./scripts/source.sh) - Sources the Nix profile or installs Nix
+* [`nix/scripts/build.sh`](./scripts/build.sh) - A wrapper around `nix-build` with sane defaults
+* [`nix/scripts/shell.sh`](./scripts/shell.sh) - A wrapper around `nix-shell` for `Makefile`
+* [`nix/scripts/clean.sh`](./scripts/clean.sh) - For cleaning Nix store after builds
+* [`nix/scripts/purge.sh`](./scripts/purge.sh) - For purging everything Nix related from system
 
 # Start
 
@@ -32,7 +45,15 @@ The starting point for using our Nix shells and targets is the [`default.nix`](/
 
 It pulls in all the `pkgs`, `targets` and `shells` defined in [`nix/default.nix`](/nix/default.nix). The point is easy access to them via commands like `nix-build` or `nix-shell`, which you'll see next.
 
-# Usage
+# Shells
+
+Normally shells are started using `make shell TARGET=android`, but that is essentially the same as calling:
+```bash
+nix-shell -A shells.android default.nix
+```
+The [`nix/scripts/shell.sh`](./scripts/shell.sh) script is essentially a wrapper around that command to make it usable as shell for the `Makefile`.
+
+# Building
 
 We will use the `make jsbundle-android` target as an example of a derivation you can build using Nix:
 

nix/README.md

@@ -10,12 +10,12 @@ __NOTE:__ If you are in Asia you might want to add the `https://nix-cache-cn.sta
 
 ## Build arguments
 
-We leverage the standard nixpkgs `config` argument for our own parameterization of the builds (e.g. to pass a build number or build type).
+We leverage the `config` argument of standard `nixpkgs` for our own parameterization of the builds (e.g. to pass a build number or build type).
 
 Here is a sample structure of the `config` attribute set:
 
 ```nix
-config = {
+{
   status-im = {
     build-type = "pr";     # Build type (influences which .env file gets used for feature flags)
     build-number = 9999;   # Used for versionCode and CFBundleVersion in Android and iOS respectively
@@ -29,7 +29,7 @@ config = {
       src-override = "$HOME/my/source/status-go"; # local source override
     };
   };
-};
+}
 ```
 You can see the defaults in [`nix/config.nix`](./config.nix).
 
@@ -59,6 +59,15 @@ export STATUS_GO_SRC_OVERRIDE=$GOPATH/src/github.com/status-im/status-go
 make release-android
 ```
 
+## Resources
+
+You can learn more about Nix by watching these presentations:
+
+* [Nix Fundamentals](https://www.youtube.com/watch?v=m4sv2M9jRLg) ([PDF](https://drive.google.com/file/d/1Tt5R7QOubudGiSuZIGxuFWB1OYgcThcL/view?usp=sharing), [src](https://github.com/status-im/infra-docs/tree/master/presentations/nix_basics))
+* [Nix in Status](https://www.youtube.com/watch?v=rEQ1EvRG8Wc) ([PDF](https://drive.google.com/file/d/1Ti0wppMoj40icCPdHy7mJcQj__DeaYBE/view?usp=sharing), [src](https://github.com/status-im/infra-docs/tree/master/presentations/nix_in_status))
+
+And you can read [`nix/DETAILS.md`](./DETAILS.md) for more information.
+
 ## Known Issues
 
 See [`KNOWN_ISSUES.md`](./KNOWN_ISSUES.md).

nix/lib/getConfig.nix

@@ -1,12 +1,11 @@
-#
 # helper for getting status-im config values in a safe way
 #
 
 { lib, config }:
 
+let inherit (lib) splitString attrByPath;
+in name: default:
 let
-  inherit (lib) splitString attrByPath;
+  path = [ "status-im" ] ++ (splitString "." name);
-in
+  value = attrByPath path default config;
-  name: default:
+in if value != null then value else default
-    let path = [ "status-im" ] ++ (splitString "." name);
-    in attrByPath path default config

nix/mobile/android/release.nix

@@ -16,7 +16,7 @@ assert (lib.stringLength watchmanSockPath) > 0 -> stdenv.isDarwin;
 
 let
   inherit (lib)
-    toLower optionalString stringLength
+    toLower optionalString stringLength assertMsg
     getConfig makeLibraryPath assertEnvVarSet;
 
   buildType = getConfig "build-type" "prod";
@@ -82,7 +82,7 @@ in stdenv.mkDerivation rec {
 
   phases = [
     "unpackPhase" "secretsPhase" "secretsCheckPhase"
-    "buildPhase" "checkPhase" "installPhase"
+    "keystorePhase" "buildPhase" "checkPhase" "installPhase"
   ];
 
   unpackPhase = ''
@@ -90,13 +90,7 @@ in stdenv.mkDerivation rec {
     chmod u+w -R ./
     runHook postUnpack
   '';
-  postUnpack = 
+  postUnpack = ''
-    assert lib.assertMsg (keystorePath != null) "keystore-file has to be set!";
-  ''
-    # Keep the same keystore path for determinism
-    export KEYSTORE_PATH="$PWD/status-im.keystore"
-    cp -a --no-preserve=ownership "${keystorePath}" "$KEYSTORE_PATH"
-
     # Ensure we have the right .env file
     cp -f ./${envFileName} ./.env
 
@@ -118,10 +112,19 @@ in stdenv.mkDerivation rec {
     # Patch build.gradle to use local repo
     ${patchMavenSources} ./android/build.gradle
   '';
+
   # if secretsFile is not set we use generate keystore
   secretsPhase = if (secretsFile != "") then ''
     source "${secretsFile}"
   '' else keystore.shellHook;
+
+  # if keystorePath is set copy it into build directory
+  keystorePhase =
+    assert assertMsg (keystorePath != null) "keystorePath has to be set!";
+  ''
+    export KEYSTORE_PATH="$PWD/status-im.keystore"
+    cp -a --no-preserve=ownership "${keystorePath}" "$KEYSTORE_PATH"
+  '';
   secretsCheckPhase = ''
     ${assertEnvVarSet "KEYSTORE_ALIAS"}
     ${assertEnvVarSet "KEYSTORE_PASSWORD"}

nix/shell.nix

@@ -0,0 +1,39 @@
+#
+# Defines the default shell that is used when target is not specified.
+# It is also merged with all the other shells for a complete set of tools.
+#
+{ config ? {}
+, pkgs ? import ./pkgs.nix { inherit config; } }:
+
+let
+  inherit (pkgs) mkShell;
+in mkShell {
+  name = "status-react-shell"; # for identifying all shells
+
+  buildInputs = with pkgs; lib.unique ([
+    # core utilities that should always be present in a shell
+    bash curl wget file unzip flock
+    git gnumake jq ncurses gnugrep parallel
+    lsof # used in start-react-native.sh
+    # build specific utilities
+    clojure maven watchman
+    # other nice to have stuff
+    yarn nodejs python27
+  ] # and some special cases
+    ++ lib.optionals stdenv.isDarwin [ cocoapods clang ]
+    ++ lib.optionals (!stdenv.isDarwin) [ gcc8 ]
+  );
+
+  # avoid terminal issues
+  TERM="xterm";
+
+  # default locale
+  LANG="en_US.UTF-8";
+  LANGUAGE="en_US.UTF-8";
+
+  # just a nicety for easy access to node scripts
+  shellHook = ''
+    export STATUS_REACT_HOME=$(git rev-parse --show-toplevel)
+    export PATH="$STATUS_REACT_HOME/node_modules/.bin:$PATH"
+  '';
+}

nix/shells.nix

@@ -1,48 +1,16 @@
 # This file defines custom shells as well as shortcuts
 # for accessing more nested shells.
-{
+{ config ? {}
-  config ? {},
+, pkgs ? import ./pkgs.nix { inherit config; } }:
-  pkgs ? import ./pkgs.nix { inherit config; }
-}:
 
 let
-  inherit (pkgs) lib stdenv mkShell;
+  inherit (pkgs) lib mkShell callPackage;
 
   # everything else we define in nix/ dir
-  targets = pkgs.callPackage ./targets.nix { inherit config; };
+  targets = callPackage ./targets.nix { inherit config; };
 
-  # the default shell that is used when target is not specified
+  # the default shell with most commonly used tools
-  # it is also merged with all the other shells
+  default = callPackage ./shell.nix { };
-  default = mkShell {
-    name = "status-react-shell"; # for identifying all shells
-
-    buildInputs = with pkgs; lib.unique ([
-      # core utilities that should always be present in a shell
-      bash curl wget file unzip flock
-      git gnumake jq ncurses gnugrep parallel
-      lsof # used in start-react-native.sh
-      # build specific utilities
-      clojure maven watchman
-      # other nice to have stuff
-      yarn nodejs python27
-    ] # and some special cases
-      ++ lib.optionals stdenv.isDarwin [ cocoapods clang ]
-      ++ lib.optionals (!stdenv.isDarwin) [ gcc8 ]
-    );
-
-    # avoid terinal issues
-    TERM="xterm";
-
-    # default locale
-    LANG="en_US.UTF-8";
-    LANGUAGE="en_US.UTF-8";
-
-    # just a nicety for easy access to node scripts
-    shellHook = ''
-      export STATUS_REACT_HOME=$(git rev-parse --show-toplevel)
-      export PATH="$STATUS_REACT_HOME/node_modules/.bin:$PATH"
-    '';
-  };
 
   # Combines with many other shells
   node-sh = mkShell {
@@ -55,6 +23,8 @@ let
 
   # An attrset for easier merging with default shell
   shells = {
+    inherit default;
+
     nodejs = node-sh;
 
     # for calling clojure targets in CI or Makefile
@@ -106,6 +76,4 @@ let
 
 # values here can be selected using `nix-shell --attr shells.$TARGET default.nix`
 # the nix/scripts/shell.sh wrapper does this for us and expects TARGET to be set
-in {
+in lib.mapAttrs mergeDefaultShell shells
-  inherit default;
-} // lib.mapAttrs mergeDefaultShell shells

shell.nix

@@ -2,7 +2,7 @@
 { config ? { } }:
 
 let
-  project = import ./default.nix { inherit config; };
+  main = import ./nix { inherit config; };
 in
-  # we use the shell combining most shells as default
+  # use the default shell when calling nix-shell without arguments
-  project.shells.default
+  main.shells.default