Implement dropping package attr

Main.hs

@@ -433,7 +433,8 @@ cmdUpdate = \case
 parseCmdDrop :: Opts.ParserInfo (IO ())
 parseCmdDrop =
     Opts.info
-      ((cmdDrop <$> parsePackageName) <**> Opts.helper) $
+      ((cmdDrop <$> parsePackageName <*> parseDropAttributes) <**>
+        Opts.helper) $
       mconcat desc
   where
     desc =
@@ -442,11 +443,16 @@ parseCmdDrop =
       , Opts.headerDoc $ Just $
           "Examples:" Opts.<$$>
           "" Opts.<$$>
-          "  niv drop jq"
+          "  niv drop jq" Opts.<$$>
+          "  niv drop my-package version"
       ]
+    parseDropAttributes :: Opts.Parser [T.Text]
+    parseDropAttributes = many $
+      Opts.argument Opts.str (Opts.metavar "ATTRIBUTE")
 
-cmdDrop :: PackageName -> IO ()
-cmdDrop packageName = do
+cmdDrop :: PackageName -> [T.Text] -> IO ()
+cmdDrop packageName = \case
+    [] -> do
       putStrLn $ "Dropping package: " <> unPackageName packageName
       sources <- unSources <$> getSources
 
@@ -455,6 +461,21 @@ cmdDrop packageName = do
 
       setSources $ Sources $
         HMap.delete packageName sources
+    attrs -> do
+      putStrLn $ "Dropping attributes :" <>
+        (T.unpack (T.intercalate " " attrs))
+      putStrLn $ "In package: " <> unPackageName packageName
+      sources <- unSources <$> getSources
+
+      packageSpec <- case HMap.lookup packageName sources of
+        Nothing ->
+          abortCannotAttributesDropNoSuchPackage packageName
+        Just (PackageSpec packageSpec) -> pure $ PackageSpec $
+          HMap.mapMaybeWithKey
+            (\k v -> if k `elem` attrs then Nothing else Just v) packageSpec
+
+      setSources $ Sources $
+        HMap.insert packageName packageSpec sources
 
 -------------------------------------------------------------------------------
 -- Aux
@@ -694,6 +715,12 @@ abortCannotDropNoSuchPackage (PackageName n) = abort $ unlines
     , "The package doesn't exist."
     ]
 
+abortCannotAttributesDropNoSuchPackage :: PackageName -> IO a
+abortCannotAttributesDropNoSuchPackage (PackageName n) = abort $ unlines
+    [ "Cannot drop attributes of package " <> n <> "."
+    , "The package doesn't exist."
+    ]
+
 abortNixPrefetchExpectedOutput :: IO a
 abortNixPrefetchExpectedOutput = abort [s|
 Could not read the output of 'nix-prefetch-url'. This is a bug. Please create a

README.md

@@ -104,8 +104,9 @@ Available options:
 Examples:
 
   niv drop jq
+  niv drop my-package version
 
-Usage: niv drop PACKAGE
+Usage: niv drop PACKAGE [ATTRIBUTE]
   Drop dependency
 
 Available options:

nix/sources.json

@@ -1 +1,23 @@
-{"nixpkgs":{"url":"https://github.com/NixOS/nixpkgs-channels/archive/138f2cc707d7ee13d93c86db3285460e244c402c.tar.gz","owner":"NixOS","branch":"nixos-18.03","url_template":"https://github.com/<owner>/<repo>/archive/<rev>.tar.gz","repo":"nixpkgs-channels","sha256":"0h49j1cbnccqx996x80z7na9p7slnj9liz646s73s55am8wc9q8q","description":"Nixpkgs/NixOS branches that track the Nixpkgs/NixOS channels","rev":"138f2cc707d7ee13d93c86db3285460e244c402c"},"snack":{"homepage":"","url":"https://github.com/nmattia/snack/archive/a4b7401cd3f7468cc3a8af1067466a96ef259d8b.tar.gz","owner":"nmattia","branch":"master","url_template":"https://github.com/<owner>/<repo>/archive/<rev>.tar.gz","repo":"snack","sha256":"1sywnk19pdj8acq9gb3sy959s55gn66x4s8z038ifimvk6xpyl50","description":"Nix-based incremental build tool for Haskell projects","rev":"a4b7401cd3f7468cc3a8af1067466a96ef259d8b"}}
+{
+    "snack": {
+        "homepage": "",
+        "url": "https://github.com/nmattia/snack/archive/a4b7401cd3f7468cc3a8af1067466a96ef259d8b.tar.gz",
+        "owner": "nmattia",
+        "branch": "master",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz",
+        "repo": "snack",
+        "sha256": "1sywnk19pdj8acq9gb3sy959s55gn66x4s8z038ifimvk6xpyl50",
+        "description": "Nix-based incremental build tool for Haskell projects",
+        "rev": "a4b7401cd3f7468cc3a8af1067466a96ef259d8b"
+    },
+    "nixpkgs": {
+        "url": "https://github.com/NixOS/nixpkgs-channels/archive/138f2cc707d7ee13d93c86db3285460e244c402c.tar.gz",
+        "owner": "NixOS",
+        "branch": "nixos-18.03",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz",
+        "repo": "nixpkgs-channels",
+        "sha256": "0h49j1cbnccqx996x80z7na9p7slnj9liz646s73s55am8wc9q8q",
+        "description": "Nixpkgs/NixOS branches that track the Nixpkgs/NixOS channels",
+        "rev": "138f2cc707d7ee13d93c86db3285460e244c402c"
+    }
+}

script/gen

@@ -0,0 +1,11 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash
+#!nix-shell -I nixpkgs=./nix
+#!nix-shell -p nix
+#!nix-shell --pure
+
+set -euo pipefail
+
+echo "Updating README"
+
+cat $(nix-build -A readme) > README.md