expanded

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@@ -8,7 +8,7 @@
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-   inkscape:version="1.2.2 (b0a8486541, 2022-12-01)"
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@@ -27,14 +27,14 @@
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source/modify-hello-flake/main.adoc0

@@ -84,7 +84,7 @@ the version in `result`.
 Now we're ready to make the flake a little more interesting.
 Instead of using the `echo` command in the script, we can use the Linux `cowsay`
 command.
-Here's the `hello-flake` file, with the modified line highlighted.
+Here's the modified `hello-flake` file.
 
 ////
 $ sed -i 's/echo/cowsay/' hello-flake
@@ -107,6 +107,7 @@ What went wrong? Remember that we are in a _development_ shell. Since
 shell only includes the Nix standard environment. In particular, the
 `cowsay` command is not available.
 
+[#hello-flake-dependency]
 To fix the problem, we can modify `flake.nix`.
 We don't need to add `cowsay` to the `inputs` section because it's included in `nixpkgs`,
 which is already an input.

source/new-flake/haskell-flake/Main.hs

@@ -0,0 +1,7 @@
+import Network.HostName
+
+main :: IO ()
+main = do
+  putStrLn "Hello from Haskell inside a Nix flake!"
+  h <- getHostName
+  putStrLn $ "Your hostname is: " ++ h

source/new-flake/haskell-flake/main.adoc0

@@ -13,7 +13,7 @@ $ git init
 Next, we'll create a simple Haskell program.
 
 ////
-$ curl https://codeberg.org/mhwombat/hello-flake-haskell/raw/branch/main/Main.hs --silent --output Main.hs
+$ cp ../Main.hs .
 ////
 
 [source,haskell,linenums]
@@ -22,10 +22,22 @@ $ curl https://codeberg.org/mhwombat/hello-flake-haskell/raw/branch/main/Main.hs
 $# cat Main.hs
 ....
 
-== (Optional) Testing before packaging
+== Running the program manually (optional)
+
+[NOTE]
+====
+In this section you will learn how to do some development tasks manually, the "hard" way.
+This can help you understand the distinction between Nix's role and
+the Haskell build system you've chosen.
+Also, if you have a build problem but you're not sure if the fault is in
+your flake definition or some other configuration file,
+these commands can help you narrow it down.
+But you may wish to skip to the <<_the_cabal_file,next section>>
+and come back here later.
+====
 
 Before we package the program, let's verify that it runs. We're going to
-need a Haskell compiler. By now you've probably figured out that we can write a
+need Haskell. By now you've probably figured out that we can write a
 `flake.nix` and define a development shell that includes Haskell. We'll
 do that shortly, but first I want to show you a handy shortcut. We can
 launch a _temporary_ shell with any Nix packages we want. This is
@@ -36,21 +48,11 @@ packages you need), and you want to experiment a bit first.
 
 The command to enter a temporary shell is
 
-`nix-shell -p __packages__`
+`nix shell -p __installables__`
 
-If there are multiple packages, they should be separated by spaces.
+Where __installables__ are flakes and other types of packages that you need.
-
+(You can learn more about these in the
-[IMPORTANT]
+https://nix.dev/manual/nix/stable/command-ref/new-cli/nix#installables[Nix manual].)
-====
-The command used here is `nix-shell` with a hyphen, not `nix shell`
-with a space; those are two different commands. In fact there are
-hyphenated and non-hyphenated versions of many Nix commands, and yes,
-it's confusing. The non-hyphenated commands were introduced when support
-for flakes was added to Nix. I predict that eventually all hyphenated
-commands will be replaced with non-hyphenated versions. Until then, a
-useful rule of thumb is that non-hyphenated commands are for working
-directly with flakes; hyphenated commands are for everything else.
-====
 
 === Some unsuitable shells
 
@@ -66,8 +68,8 @@ You can come back to this section later to learn more.
 Let's enter a shell with the Glasgow Haskell Compiler ("ghc") and try to run the program.
 
 ....
-$# echo '$ nix-shell -p ghc'
+$# echo '$ nix shell nixpkgs#ghc'
-$# nix-shell -p ghc --command sh
+$# nix shell nixpkgs#ghc --command sh
 $ runghc Main.hs
 ....
 
@@ -77,8 +79,8 @@ Let's exit that shell and try again, this time adding the `hostname` package.
 
 ....
 $# echo '$ exit'
-$# echo '$ nix-shell -p "[ghc hostname]"'
+$# echo '$ nix shell nixpkgs#ghc nixpkgs#hostname'
-$# nix-shell -p "[ghc hostname]" --command sh
+$# nix shell nixpkgs#ghc nixpkgs#hostname --command sh
 $ runghc Main.hs
 ....
 
@@ -91,39 +93,29 @@ Let's try that again, with the correct package.
 
 ....
 $# echo '$ exit'
-$# echo '$ nix-shell -p "[ghc haskellPackages.hostname]"'
+$# echo '$ nix shell nixpkgs#ghc nixpkgs#haskellPackages.hostname'
-$# nix-shell -p "[ghc haskellPackages.hostname]" --command sh
+$# nix shell nixpkgs#ghc nixpkgs#haskellPackages.hostname --command sh
 $ runghc Main.hs
 ....
 
 Now what's wrong?
-The syntax we used in the `nix-shell` command above is fine, but it doesn't make the package _available to GHC_!
+The syntax we used in the `nix shell` command above is fine,
+but it doesn't make the package _available to GHC_!
 
 === A suitable shell for a quick test
 
-Consider the Haskell "pandoc" package, which provides both an executable (the Nix package `pandoc`)
+Now we will create a shell that can run the program.
-and a library (the Nix package `haskellPackages.pandoc`).
+When you need support for both a language and some of
-There are several different shells we could create involving both Pandoc and GHC,
+its packages, it's best to use one of the Nix functions that are
-and it's important to understand the differences between them.
+specific to the programming language and build system.
-
+For Haskell, we can use the `ghcWithPackages` function.
-[cols="1,1"]
+The command below is rather complex,
-|===
+and a complete explanation would be rather lengthy.
-|`nix-shell -p "[ghc pandoc]"`
-|Makes the Pandoc _executable_ available at the command line, but the _library_ won't be visible to GHC.
-
-|`nix-shell -p "haskellPackages.ghcWithPackages (pkgs: with pkgs; [ pandoc ])"`
-|Makes the Pandoc _library_ visible to GHC, but we won't be able to run the _executable_.
-
-|`nix-shell -p "[pandoc (haskellPackages.ghcWithPackages (pkgs: with pkgs; [ pandoc ]))]"`
-|Makes the Pandoc _executable_ available at the command line, and the _library_ visible to GHC.
-|===
-
-
-Now we can create a shell that can run the program.
 
+[#haskell-nix-shell]
 ....
-$# echo '$ nix-shell -p "haskellPackages.ghcWithPackages (pkgs: with pkgs; [ hostname ])"'
+$# echo '$ nix shell --impure --expr '"'"'with import <nixpkgs> {}; haskellPackages.ghcWithPackages (p: [ p.hostname ])'"'"
-$# nix-shell -p "haskellPackages.ghcWithPackages (pkgs: with pkgs; [ hostname ])" --command sh
+$# nix shell --impure --expr 'with import <nixpkgs> {}; haskellPackages.ghcWithPackages (p: [ p.hostname ])' --command sh
 $ runghc Main.hs
 ....
 
@@ -133,14 +125,13 @@ Success! Now we know the program works.
 $# echo '$ exit'
 ....
 
-
 == The cabal file
 
 It's time to write a Cabal file for this program.
 This is just an ordinary Cabal file; we don't need to do anything special for Nix.
 
 ////
-$ curl https://codeberg.org/mhwombat/hello-flake-haskell/raw/branch/main/hello-flake-haskell.cabal --silent --output hello-flake-haskell.cabal
+$ cp ../hello-flake-haskell.cabal .
 ////
 
 [source,cabal,linenums]
@@ -149,55 +140,77 @@ $ curl https://codeberg.org/mhwombat/hello-flake-haskell/raw/branch/main/hello-f
 $# cat hello-flake-haskell.cabal
 ....
 
+== Building the program manually (optional)
 
-== (Optional) Building and running with cabal-install
+[NOTE]
-
+====
-At this point, I would normally write `flake.nix` and use Nix to build the program.
+In this section you will learn how to do some development tasks manually, the "hard" way.
-I'll cover that in the next section.
+This can help you understand the distinction between Nix's role and
-However, it's useful to know how to build the package manually in a Nix environment,
+the Haskell build system you've chosen.
-without using a Nix flake.
+Also, if you have a build problem but you're not sure if the fault is in
-When you're new to Nix, this can help you differentiate between problems in your flake definition
+your flake definition or some other configuration file,
-and problems in your Cabal file.
+these commands can help you narrow it down.
+But you may wish to skip to the <<haskell-flake,next section>>
+and come back here later.
+====
 
+We won't write `flake.nix` just yet.
+First we'll try building the package manually.
+(If you didn't run the `nix shell` command from <<haskell-nix-shell,earlier>>, do so now.)
 ....
 $ cabal build
 ....
 
-Aha! We need `cabal-install` in our shell.
+The `cabal` command is provided by the `cabal-install` package.
-Rather than launch another shell-within-a-shell, let's exit create a new one.
+The error happens because we don't have `cabal-install` available
+in the temporary shell.
+We can correct that.
 
 ....
-$# echo '$ exit'
+$# echo '$ nix shell --impure --expr '"'"'with import <nixpkgs> {}; haskellPackages.ghcWithPackages (p: [ p.hostname p.cabal-install ])'"'"
-$# echo '$ nix-shell -p "[ cabal-install (haskellPackages.ghcWithPackages (pkgs: with pkgs; [ hostname ]))]"'
+$# nix shell --impure --expr 'with import <nixpkgs> {}; haskellPackages.ghcWithPackages (p: [ p.hostname p.cabal-install ])' --command sh
-$# nix-shell -p "[ cabal-install (haskellPackages.ghcWithPackages (pkgs: with pkgs; [ hostname ]))]" --command sh
-$ cabal build
-$ cabal run
-$# echo '$ exit'
 ....
 
-After some output messages, the build succeeds and the program runs.
+Note that we're now inside a temporary shell inside the previous
+temporary shell! To get back to the original shell, we have to `exit`
+twice.
+Alternatively, we could have done `exit` followed by the
+second `nix-shell` command.
 
+....
+$# echo '$ cabal build'
+$# echo ". . ."
+$# cabal build |& tail -n 4
+....
+
+After a lot of output messages, the build succeeds.
+
+[#haskell-flake]
 == The Nix flake
 
-Now we should write `flake.nix`. We already know how to write most of
+Now we should write `flake.nix`.
-the flake from the examples we did earlier. The two parts that would be
+We already know how to write most of the flake from the examples we did earlier.
-different are the development shell and the package builder.
+The two parts that will be different are the development shell and the package builder.
 
-However, there's a simpler way, using `haskell-flake`.
+However, there's a _much_ simpler way, using `haskell-flake`.
+The following command will create `flake.nix` based on their template.
 
-////
+....
-$ curl https://codeberg.org/mhwombat/hello-flake-haskell/raw/branch/main/flake.nix --silent --output flake.nix
+$ nix flake init -t github:srid/haskell-flake
-////
+....
 
-[source,nix,linenums]
+Examining the flake,
+you'll notice that it is well-commented.
+The only thing we need to change for now is the name in `packages.default`;
+I've highlighted the change below.
+
+[source,nix,linenums,highlight=55]
 .flake.nix
 ....
+$# sed -i 's/example/hello-flake-haskell/' flake.nix
 $# cat flake.nix
 ....
 
-The above definition will work for most of your haskell projects;
-simply change the `description` and the package name in `packages.default`.
-
 We also need a `LICENSE` file.
 For now, this can be empty.
 
@@ -205,25 +218,37 @@ For now, this can be empty.
 $ touch LICENSE
 ....
 
+== Building the program
+
 Let's try out the new flake.
-
+Nix flakes only "`see`" files that are
-....
-$ nix run
-....
-
-Why can't it find `flake.nix`? Nix flakes only "`see`" files that are
 part of the repository. We need to add all of the important files to the
 repo before building or running the flake.
 
 ....
 $ git add flake.nix hello-flake-haskell.cabal LICENSE Main.hs
+$ nix build
+....
+
+We'll deal with those warnings later.
+The important thing for now is that the build succeeded.
+
+== Running the program
+
+Now we can run the program.
+
+....
 $ nix run
 ....
 
+By the way, we didn't need to do `nix build` earlier.
+The `nix run` command will first build the program for us if needed.
+
 We'd like to share this package with others, but first we should do some
-cleanup. When the package was built (automatically by the `nix run`
+cleanup.
-command), it created a `flake.lock` file. We need to add this to the
+It's time to deal with those warnings.
-repo, and commit all important files.
+When the package was built, Nix created a `flake.lock` file.
+We need to add this to the repo, and commit all important files.
 
 ....
 $ git add flake.lock

source/new-flake/python-flake/main.adoc0

@@ -22,6 +22,20 @@ $ curl https://codeberg.org/mhwombat/hello-flake-python/raw/branch/main/hello.py
 $# cat hello.py
 ....
 
+== Running the program manually (optional)
+
+[NOTE]
+====
+In this section you will learn how to do some development tasks manually, the "hard" way.
+This can help you understand the distinction between Nix's role and
+the Python build system you've chosen.
+Also, if you have a build problem but you're not sure if the fault is in
+your flake definition or some other configuration file,
+these commands can help you narrow it down.
+But you may wish to skip to the <<_configuring_setuptools,next section>>
+and come back here later.
+====
+
 Before we package the program, let's verify that it runs. We're going to
 need Python. By now you've probably figured out that we can write a
 `flake.nix` and define a development shell that includes Python. We'll
@@ -34,31 +48,22 @@ packages you need), and you want to experiment a bit first.
 
 The command to enter a temporary shell is
 
-`nix-shell -p __packages__`
+`nix shell -p __installables__`
 
-If there are multiple packages, they should be separated by spaces.
+Where __installables__ are flakes and other types of packages that you need.
-
+(You can learn more about these in the
-[NOTE]
+https://nix.dev/manual/nix/stable/command-ref/new-cli/nix#installables[Nix manual].)
-====
-The command used here is `nix-shell` with a hyphen, not `nix shell`
-with a space; those are two different commands. In fact there are
-hyphenated and non-hyphenated versions of many Nix commands, and yes,
-it's confusing. The non-hyphenated commands were introduced when support
-for flakes was added to Nix. I predict that eventually all hyphenated
-commands will be replaced with non-hyphenated versions. Until then, a
-useful rule of thumb is that non-hyphenated commands are for for working
-directly with flakes; hyphenated commands are for everything else.
-====
 
 Let's enter a shell with Python so we can test the program.
 
+[#python-nix-shell]
 ....
-$# echo '$ nix-shell -p python3'
+$# echo '$ nix shell nixpkgs#python3'
-$# nix-shell -p python3 --command sh
+$# nix shell nixpkgs#python3 --command sh
 $ python hello.py
 ....
 
-== A Python builder
+== Configuring setuptools
 
 Next, create a Python script to build the package. We'll use Python's
 setuptools, but you can use other build tools. For more information on
@@ -78,9 +83,23 @@ $ curl https://codeberg.org/mhwombat/hello-flake-python/raw/branch/main/setup.py
 $# cat setup.py
 ....
 
-We won't write `flake.nix` just yet. First we'll try building the
+== Building the program manually (optional)
-package manually.
 
+[NOTE]
+====
+In this section you will learn how to do some development tasks manually, the "hard" way.
+This can help you understand the distinction between Nix's role and
+the Python build system you've chosen.
+Also, if you have a build problem but you're not sure if the fault is in
+your flake definition or some other configuration file,
+these commands can help you narrow it down.
+But you may wish to skip to the <<python-flake,next section>>
+and come back here later.
+====
+
+We won't write `flake.nix` just yet.
+First we'll try building the package manually.
+(If you didn't run the `nix shell` command from <<python-nix-shell,earlier>>, do so now.)
 ....
 $ python -m build
 ....
@@ -99,8 +118,9 @@ $# nix-shell -p "python3.withPackages (ps: with ps; [ build ])" --command sh
 
 Note that we're now inside a temporary shell inside the previous
 temporary shell! To get back to the original shell, we have to `exit`
-twice. Alternatively, we could have done `exit` followed by the
+twice.
-`nix-shell` command.
+Alternatively, we could have done `exit` followed by the
+second `nix-shell` command.
 
 ....
 $# echo '$ python -m build'
@@ -109,11 +129,12 @@ $# python -m build > /dev/null 2>&1
 
 After a lot of output messages, the build succeeds.
 
+[#python-flake]
 == The Nix flake
 
-Now we should write `flake.nix`. We already know how to write most of
+Now we should write `flake.nix`.
-the flake from the examples we did earlier. The two parts that will be
+We already know how to write most of the flake from the examples we did earlier.
-different are the development shell and the package builder.
+The two parts that will be different are the development shell and the package builder.
 
 Let's start with the development shell. It seems logical to write
 something like the following.
@@ -172,10 +193,12 @@ $ curl https://codeberg.org/mhwombat/hello-flake-python/raw/branch/main/flake.ni
 $# cat flake.nix
 ....
 
+== Building the program
+
 Let's try out the new flake.
 
 ....
-$ nix run
+$ nix build
 ....
 
 Why can't it find `flake.nix`? Nix flakes only "`see`" files that are
@@ -184,13 +207,28 @@ repo before building or running the flake.
 
 ....
 $ git add flake.nix setup.py hello.py
+$ nix build
+....
+
+We'll deal with those warnings later.
+The important thing for now is that the build succeeded.
+
+== Running the program
+
+Now we can run the program.
+
+....
 $ nix run
 ....
 
+By the way, we didn't need to do `nix build` earlier.
+The `nix run` command will first build the program for us if needed.
+
 We'd like to share this package with others, but first we should do some
-cleanup. When the package was built (automatically by the `nix run`
+cleanup.
-command), it created a `flake.lock` file. We need to add this to the
+It's time to deal with those warnings.
-repo, and commit all important files.
+When the package was built, Nix created a `flake.lock` file.
+We need to add this to the repo, and commit all important files.
 
 ....
 $ git add flake.lock

source/recipes/nixpkgs-pkg/cli/main.adoc0

@@ -1,4 +1,14 @@
-= From the command line
+= From the command line (flake style)
+
+....
+$# echo '$ nix shell nixpkgs#hello nixpkgs#cowsay --command bash'
+$# nix shell nixpkgs#hello nixpkgs#cowsay --command bash <<EOL
+$ hello
+$ cowsay "moo"
+$# EOL
+....
+
+= From the command line (non-flake style)
 
 ....
 $# echo '$ nix-shell -p "[hello cowsay]"'

source/recipes/nixpkgs-pkg/shebang/main.adoc0

@@ -1,4 +1,17 @@
-= In a Bash script
+= In a Bash script (flake style)
+
+[source,bash,linenums]
+.Script
+....
+include::my-flake-script.sh[]
+....
+
+.Output
+....
+$# ./my-flake-script.sh
+....
+
+= In a Bash script (non-flake style)
 
 [source,bash,linenums]
 .Script

source/recipes/nixpkgs-pkg/shell/main.adoc0

@@ -1,3 +1,10 @@
+= In `flake.nix`
+
+See the example in <<_introducing_a_dependency>>
+where defined a development shell in <<hello-flake-dependency,flake.nix>>
+with a dependency on `cowsay` ,
+and tested the shell.
+
 = In `shell.nix`
 
 [source,nix,linenums]

source/recipes/remote-git/flake/flake.nix

@@ -0,0 +1,54 @@
+{
+  # See https://github.com/mhwombat/nix-for-numbskulls/blob/main/flakes.md
+  # for a brief overview of what each section in a flake should or can contain.
+
+  description = "a sample flake";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs";
+    flake-utils.url = "github:numtide/flake-utils";
+    hello-nix = {
+              url = "git+https://codeberg.org/mhwombat/hello-nix";
+              flake = false;
+            };
+  };
+
+  outputs = { self, nixpkgs, flake-utils, hello-nix }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs { inherit system; };
+      in
+      {
+        devShells = rec {
+          default = pkgs.mkShell {
+            packages = [ hello-nix ];
+          };
+        };
+
+        packages = rec {
+          hello = pkgs.stdenv.mkDerivation rec {
+            name = "hello-again";
+
+            src = ./.;
+
+            unpackPhase = "true";
+
+            buildPhase = ":";
+
+            installPhase =
+              ''
+                mkdir -p $out/bin
+                cp $src/hello-again $out/bin/hello-again
+                chmod +x $out/bin/hello-again
+              '';
+          };
+          default = hello;
+        };
+
+        apps = rec {
+          hello = flake-utils.lib.mkApp { drv = self.packages.${system}.hello; };
+          default = hello;
+        };
+      }
+    );
+}

source/recipes/remote-git/flake/hello-again

@@ -0,0 +1,4 @@
+#!/usr/bin/env sh
+
+echo "I'm a flake, but I'm running a command defined in a non-flake package."
+hello-nix

source/recipes/remote-git/main.adoc

@@ -1,6 +1,6 @@
 = Access to a package defined in a remote git repo
 
-Ex: Access a package called `hello-nix`,
+Ex: Access a package (not a flake) called `hello-nix`,
 which is defined in a remote git repo on codeberg.
 To use a package from GitHub, GitLab, or any other public platform,
 modify the URL.