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+ +In this repo, each flake's README.md assumes that the directory of its flake.nix is your current working directory in a terminal.
To de-duplicate the docs, one of the top sections of each README.md here contains a Prerequisites section. This section provides the links to other sections that possibly contain the relevant docs. Sometimes, you'll need to traverse multiple Prerequisites before you achieve the relevant docs.
I inserted a number of binary caches into nixConfig attribute of each flake.nix.
+These caches should accelerate builds.
+You can add an accept-flake-config to your nix.conf.
Sometimes, I put dev tools into a nix-dev directory.
+Then, I enter a devshell as follows.
nix develop nix-dev/
+All flakes in this repo access some other flakes from this repo via GitHub URLs.
+Let's consider two flakes from this repo, A and B, where A is in inputs of B.
+If I change the flake A, I:
A changes to GitHub.flake.lock of B.Whenever there's a push to the remote GitHub repo, B's flake.lock is updated by a GitHub Action.
+That's why, if that action works, there's no need to commit and push flake.lock changes.
+After an update is complete, it's necessary to rebase local changes onto remote changes.
+However, sometimes, there are local uncommitted changes already.
+These changes should be git stashed before doing git rebase.
+After rebasing, they can be git stash popped to continue the work.
Thus, the process is as follows:
+# can be omitted in case of automatic fetches
+git fetch
+git rebase --autostash
+git push
+Each derivation that evaluates to an executable should have these attributes:
+meta.description
+CommonMarkmeta.longDescription
+CommonMarkman pages for executableslongDescription should be recognizable by pandoc
+Templates provide extensive information about setting up development environment and packaging Haskell apps.
+ +ghcid is a Very low feature GHCi based IDE.
+It can be used to re-run a function in a given file on changes in a given directory.
+This template provides a sample configuration for this tool in the .ghcid file.
hpack translates package.yaml into .cabal.
Uses haskell4nix.
+Stack support Nix integration.
+Stack uses nix-shell.
+The name of the file providing a Nix shell can be customized in stack.yaml.
Here's the format of that file - docs.
+The shell file can import the contents of flake.nix via flake-compat.
flake.nix provides an output stack-shell.${system} = {version}: ....
stack.nix imports flake.nix and provides a shell.
devShells.default = pkgs.mkShell {
+ buildInputs = [ packageExe ];
+ shellHook = ''
+ source ${packageExe}/share/bash-completion/completions/${packageExecutableName}
+ '';
+ };
+Sometimes, HLS finds errors in code despite cabal build running successfully.
+If you use VS Code, find Outputs of Haskell Language Server and determine the cache directory for a project.
It should have approximately this form: /home/<user name>/.cache/hie-bios/dist-<project-name>-<something>.
+Remove it and restart HLS.
Install Nix (Single-user installation)
+sh <(curl -L https://nixos.org/nix/install) --no-daemon
+Enable flakes
+Set show-trace = true (doc) to see more complete error messages.
Sometimes, when you enter a devshell (e.g., nix develop) or run a default package of a flake, you may see:
y (the simplest way)This is a tool for running scripts in .envrc files when you enter a directory containing such file.
+One of its usages with flakes is to automatically build, cache, and enter a devshell when you enter that flake's directory in a terminal.
+See Direnv integration
direnv - src
+Install the binary
+nix profile install nixpkgs#direnv
+Hook into your devshell
+When you see direnv errors, run the suggested commands
Nix language
+
+I added bookmarks for search engines in my browser, like described here.
+Docs are usually left as comments in Nix code. You can find an attribute in nix-repl and look up its comments in a file at a given position.
nix repl
+nix-repl> :lf nixpkgs
+nix-repl> legacyPackages.x86_64-linux.lib.lists.singleton
+«lambda @ /nix/store/24akvz6idhp4lxxvhbfxxq84py30v6bw-source/lib/lists.nix:23:15»
+Sometimes, you may evaluate a description or a longDescription of a derivation:
nix-repl> legacyPackages.x86_64-linux.coreutils.meta.longDescription
+"The GNU Core Utilities are the basic file, shell and text manipulation\nutilities of the GNU operating system. These are the core utilities which\nare expected to exist on every operating system.\n"
+Learn about a command:
+nix help command
+Search for a package description:
+nix edit nixpkgs#coreutils
+If a flake.nix contains a valid output templates, these templates can be listed.
+List flake outputs and search for templates in this (flakes) repository:
nix flake show | grep template
+└───templates
+evaluating '' ├───codium-generic: template: `VSCodium` with extensions and executables
+ ├───codium-haskell: template: `VSCodium` with extensions and executables for `Haskell`. Shows 5 ways to run a `Haskell` app.
+evaluating '' ├───codium-haskell-simple: template: `VSCodium` with extensions and executables for `Haskell`.
+evaluating '' ├───codium-python: template: `VSCodium` with extensions and executables for `Python`.
+ └───haskell-minimal: template: Minimal flake for a `Haskell` package development.
+Two ways of copying from templates:
+ +If you notice that nix flake init, nix flake new, etc. give you an old version of a template, run nix flake lock on that template. This action will force nix to update the cached version of the template somewhere in ~/.cache/nix. - src
Templates can be accessed in Nix store via nix repl:
nix repl
+nix-repl> :lf .
+nix-repl> templates.<TAB>
+nix-repl> templates.codium-generic.path
+/nix/store/j3kx4dk567y483pvszr2w8ghnkxich3d-source/templates/codium/generic
+Templates may contain arbitrary files. This feature enables the following assembly:
+nix flake new flake-1 -t flake1
+nix flake new flake-2 -t flake2
+nix flake new flake-3 -t flake3
+cp flake-1/file1 flake-3
+cp flake-2/file{2,3} flake-3
+What are flakes? How to enable flakes? - wiki
+Nix manual answers the following questions:
+Nix store pathderivation can become an executable, and that executable can be used in build scripts of other derivationsflake.lock is usedinputs and outputs.inputs and outputs have specifications described in Nix manual.outputs?outputs? (described at the bottom)nixConfignix flake shownix flake metadatanix repl
+nix-repl> :lf nixpkgs - load flake nixpkgsderivations used to build a specific derivation?
+nix show-derivationnix shellnix profilenixpkgs to a specific commit SHA?
+nix registryHow to add a flake to a project?
+git to track flake files. So, adding a flake.nix to a project requires the following steps:
+git init - initialize a git repositoryflake.nix in some way (copy the existing flake.nix, nix flake init, etc.)git add flake.nixflake.lock in some way (copy the relevant existing flake.lock, generate a new one via nix flake update, etc.)git add flake.lockgit commit these filesHow to use the same flake inputs in all projects?
+ +How to bring any files into a flake?
+git update-index --assume-unchanged <file> for each <file>.How to enable a specific version of nix on my system? Approximately so:
nix registry remove nix
+nix registry add nix github:NixOS/nix/4bf70b74a78bf10f3f19ed122ae7377963e14003
+nix profile install nix --priority 4
+How to pin nixpkgs?
When should I use overlays over nixpkgs? - You shouldn't
How to convert an exising project to flakes? - tutorial
+How to use a .gitignored file inside a flake?
build with --impure
zxcTest = prev.writeText "zxcTest" (builtins.readFile /home/name_snrl/nixos-configuration/<fileFromIgnore>);
+Provide it in inputs. Inputs accept arbitrary files. Make links follow the format of flake inputs
+How to disable querying remote binary caches?
+nix run <installable> --no-substitutepkgs.mkShell
+3. devshell
+4. Add environment variables if necessary. E.g., using Nix store paths post
+5. Symlink a path from Nix store to make files available to NodeJS - NixOS: The Ultimate Dev Environment?GitHub ActionsRun a binary from nixpkgs:
nix run nixpkgs#nixpkgs-fmt -- hello-flake/flake.nix
+What is expression, closure, derivation?
How to get a path of a derivation in store in a .nix file?: ${drv}
There are phases
+ +When derivations are built, they may produce executables. Locations of these executables are determined by bash scripts. If you make a derivation you can use buildInputs to specify the derivations you'd like to be accessible during in scripts during phases or in a shellHook
How to access a $out folder of a derivation drv?
${drv.out};Programs can be specified in buildInputs or called by name {pkgs.hello}/bin/hello
How to wrap an executable to run it with flags?
+pkgs.runCommand in Wrapping PackagesHow to rename an executable and supply runtime dependencies?
+wrapProgram provided by pkgs.makeBinaryWrapper (docs, src).hello =
+pkgs.symlinkJoin {
+ name = "hello";
+ paths = [ hello ];
+ buildInputs = [ pkgs.makeWrapper ];
+ postBuild = ''
+ wrapProgram $out/bin/hello \
+ --set PATH ${
+ pkgs.lib.makeBinPath [
+ pkgs.cowsay
+ ]
+ }
+ '';
+};
+How to escape a shell/bash command?
+2. pkgs.lib.escapeShellArg
How to see binaries that a package provides?
+2. find $(nix build nixpkgs#hello --no-link --print-out-paths)/bin -mindepth 1
It's possible to use nix commands inside scripts
nix-instantiate --eval --strict -E "import ./settings.nix" - print contents of a nix filenixpkgs: nix run ${pkgs}#nixpkgs-fmt $nix_pathHow to package a script? +2. pkgs.writeScriptBin
+How to remove build deps from runtime deps?
+How to use parallel builds? - docs
+flake-compat to create default.nix and shell.nixnixpkgs.lib
$ nix repl
+nix-repl> :lf nixpkgs
+nix-repl> lib.or true false
+Symlinked things cannot be written or opened. They should first be removed - src
+pkgs.dockerTools.buildLayeredImage - build a docker image
config.Entrypoint = [ command ]. No need for bashdocker inspect the imageSee Haskell
+This is not a problem. Just read the text and answer. When asked like:
+do you want to allow configuration setting 'extra-trusted-substituters' to be set to 'https://haskell-language-server.cachix.org https://nix-community.cachix.org https://cache.iog.io https://deemp.cachix.org' (y/N)?
+answer y.
And then, when asked
+do you want to permanently mark this value as trusted (y/N)?
+answer y again. This is to let you use the binary caches listed by the flake.
To provide binary caches, flake.nix files specify nixConfig.extra-trusted-substituters. If you try, e.g., nix develop, and Nix unsuccessfully tries to download from a cache several times, this cache has probably failed. Comment out the lines containing its URL address in extra-trusted-substituters.
Repair a derivation - manual
+Alternative steps:
+flake.nixflake.nix by . name your-corrupt-derivationpackages.default = your-corrupt-derivation in this flake.nixnix store repair .#
+.# denotes an installableSee Locales
+ +Install Nix (Single-user installation)
+sh <(curl -L https://nixos.org/nix/install) --no-daemon
+Enable flakes
+Set show-trace = true (doc) to see more complete error messages.
Sometimes, when you enter a devshell (e.g., nix develop) or run a default package of a flake, you may see:
y (the simplest way)This is a tool for running scripts in .envrc files when you enter a directory containing such file.
+One of its usages with flakes is to automatically build, cache, and enter a devshell when you enter that flake's directory in a terminal.
+See Direnv integration
direnv - src
+Install the binary
+nix profile install nixpkgs#direnv
+Hook into your devshell
+When you see direnv errors, run the suggested commands
Install Nix (Single-user installation)
+sh <(curl -L https://nixos.org/nix/install) --no-daemon
+Enable flakes
+Set show-trace = true (doc) to see more complete error messages.
Sometimes, when you enter a devshell (e.g., nix develop) or run a default package of a flake, you may see:
y (the simplest way)This is a tool for running scripts in .envrc files when you enter a directory containing such file.
+One of its usages with flakes is to automatically build, cache, and enter a devshell when you enter that flake's directory in a terminal.
+See Direnv integration
direnv - src
+Install the binary
+nix profile install nixpkgs#direnv
+Hook into your devshell
+When you see direnv errors, run the suggested commands
Nix language
+
+I added bookmarks for search engines in my browser, like described here.
+Docs are usually left as comments in Nix code. You can find an attribute in nix-repl and look up its comments in a file at a given position.
nix repl
+nix-repl> :lf nixpkgs
+nix-repl> legacyPackages.x86_64-linux.lib.lists.singleton
+«lambda @ /nix/store/24akvz6idhp4lxxvhbfxxq84py30v6bw-source/lib/lists.nix:23:15»
+Sometimes, you may evaluate a description or a longDescription of a derivation:
nix-repl> legacyPackages.x86_64-linux.coreutils.meta.longDescription
+"The GNU Core Utilities are the basic file, shell and text manipulation\nutilities of the GNU operating system. These are the core utilities which\nare expected to exist on every operating system.\n"
+Learn about a command:
+nix help command
+Search for a package description:
+nix edit nixpkgs#coreutils
+If a flake.nix contains a valid output templates, these templates can be listed.
+List flake outputs and search for templates in this (flakes) repository:
nix flake show | grep template
+└───templates
+evaluating '' ├───codium-generic: template: `VSCodium` with extensions and executables
+ ├───codium-haskell: template: `VSCodium` with extensions and executables for `Haskell`. Shows 5 ways to run a `Haskell` app.
+evaluating '' ├───codium-haskell-simple: template: `VSCodium` with extensions and executables for `Haskell`.
+evaluating '' ├───codium-python: template: `VSCodium` with extensions and executables for `Python`.
+ └───haskell-minimal: template: Minimal flake for a `Haskell` package development.
+Two ways of copying from templates:
+ +If you notice that nix flake init, nix flake new, etc. give you an old version of a template, run nix flake lock on that template. This action will force nix to update the cached version of the template somewhere in ~/.cache/nix. - src
Templates can be accessed in Nix store via nix repl:
nix repl
+nix-repl> :lf .
+nix-repl> templates.<TAB>
+nix-repl> templates.codium-generic.path
+/nix/store/j3kx4dk567y483pvszr2w8ghnkxich3d-source/templates/codium/generic
+Templates may contain arbitrary files. This feature enables the following assembly:
+nix flake new flake-1 -t flake1
+nix flake new flake-2 -t flake2
+nix flake new flake-3 -t flake3
+cp flake-1/file1 flake-3
+cp flake-2/file{2,3} flake-3
+What are flakes? How to enable flakes? - wiki
+Nix manual answers the following questions:
+Nix store pathderivation can become an executable, and that executable can be used in build scripts of other derivationsflake.lock is usedinputs and outputs.inputs and outputs have specifications described in Nix manual.outputs?outputs? (described at the bottom)nixConfignix flake shownix flake metadatanix repl
+nix-repl> :lf nixpkgs - load flake nixpkgsderivations used to build a specific derivation?
+nix show-derivationnix shellnix profilenixpkgs to a specific commit SHA?
+nix registryHow to add a flake to a project?
+git to track flake files. So, adding a flake.nix to a project requires the following steps:
+git init - initialize a git repositoryflake.nix in some way (copy the existing flake.nix, nix flake init, etc.)git add flake.nixflake.lock in some way (copy the relevant existing flake.lock, generate a new one via nix flake update, etc.)git add flake.lockgit commit these filesHow to use the same flake inputs in all projects?
+ +How to bring any files into a flake?
+git update-index --assume-unchanged <file> for each <file>.How to enable a specific version of nix on my system? Approximately so:
nix registry remove nix
+nix registry add nix github:NixOS/nix/4bf70b74a78bf10f3f19ed122ae7377963e14003
+nix profile install nix --priority 4
+How to pin nixpkgs?
When should I use overlays over nixpkgs? - You shouldn't
How to convert an exising project to flakes? - tutorial
+How to use a .gitignored file inside a flake?
build with --impure
zxcTest = prev.writeText "zxcTest" (builtins.readFile /home/name_snrl/nixos-configuration/<fileFromIgnore>);
+Provide it in inputs. Inputs accept arbitrary files. Make links follow the format of flake inputs
+How to disable querying remote binary caches?
+nix run <installable> --no-substitutepkgs.mkShell
+3. devshell
+4. Add environment variables if necessary. E.g., using Nix store paths post
+5. Symlink a path from Nix store to make files available to NodeJS - NixOS: The Ultimate Dev Environment?GitHub ActionsRun a binary from nixpkgs:
nix run nixpkgs#nixpkgs-fmt -- hello-flake/flake.nix
+What is expression, closure, derivation?
How to get a path of a derivation in store in a .nix file?: ${drv}
There are phases
+ +When derivations are built, they may produce executables. Locations of these executables are determined by bash scripts. If you make a derivation you can use buildInputs to specify the derivations you'd like to be accessible during in scripts during phases or in a shellHook
How to access a $out folder of a derivation drv?
${drv.out};Programs can be specified in buildInputs or called by name {pkgs.hello}/bin/hello
How to wrap an executable to run it with flags?
+pkgs.runCommand in Wrapping PackagesHow to rename an executable and supply runtime dependencies?
+wrapProgram provided by pkgs.makeBinaryWrapper (docs, src).hello =
+pkgs.symlinkJoin {
+ name = "hello";
+ paths = [ hello ];
+ buildInputs = [ pkgs.makeWrapper ];
+ postBuild = ''
+ wrapProgram $out/bin/hello \
+ --set PATH ${
+ pkgs.lib.makeBinPath [
+ pkgs.cowsay
+ ]
+ }
+ '';
+};
+How to escape a shell/bash command?
+2. pkgs.lib.escapeShellArg
How to see binaries that a package provides?
+2. find $(nix build nixpkgs#hello --no-link --print-out-paths)/bin -mindepth 1
It's possible to use nix commands inside scripts
nix-instantiate --eval --strict -E "import ./settings.nix" - print contents of a nix filenixpkgs: nix run ${pkgs}#nixpkgs-fmt $nix_pathHow to package a script? +2. pkgs.writeScriptBin
+How to remove build deps from runtime deps?
+How to use parallel builds? - docs
+flake-compat to create default.nix and shell.nixnixpkgs.lib
$ nix repl
+nix-repl> :lf nixpkgs
+nix-repl> lib.or true false
+Symlinked things cannot be written or opened. They should first be removed - src
+pkgs.dockerTools.buildLayeredImage - build a docker image
config.Entrypoint = [ command ]. No need for bashdocker inspect the imageSee Haskell
+In this repo, each flake's README.md assumes that the directory of its flake.nix is your current working directory in a terminal.
To de-duplicate the docs, one of the top sections of each README.md here contains a Prerequisites section. This section provides the links to other sections that possibly contain the relevant docs. Sometimes, you'll need to traverse multiple Prerequisites before you achieve the relevant docs.
I inserted a number of binary caches into nixConfig attribute of each flake.nix.
+These caches should accelerate builds.
+You can add an accept-flake-config to your nix.conf.
Sometimes, I put dev tools into a nix-dev directory.
+Then, I enter a devshell as follows.
nix develop nix-dev/
+All flakes in this repo access some other flakes from this repo via GitHub URLs.
+Let's consider two flakes from this repo, A and B, where A is in inputs of B.
+If I change the flake A, I:
A changes to GitHub.flake.lock of B.Whenever there's a push to the remote GitHub repo, B's flake.lock is updated by a GitHub Action.
+That's why, if that action works, there's no need to commit and push flake.lock changes.
+After an update is complete, it's necessary to rebase local changes onto remote changes.
+However, sometimes, there are local uncommitted changes already.
+These changes should be git stashed before doing git rebase.
+After rebasing, they can be git stash popped to continue the work.
Thus, the process is as follows:
+# can be omitted in case of automatic fetches
+git fetch
+git rebase --autostash
+git push
+Each derivation that evaluates to an executable should have these attributes:
+meta.description
+CommonMarkmeta.longDescription
+CommonMarkman pages for executableslongDescription should be recognizable by pandoc
+This is not a problem. Just read the text and answer. When asked like:
+do you want to allow configuration setting 'extra-trusted-substituters' to be set to 'https://haskell-language-server.cachix.org https://nix-community.cachix.org https://cache.iog.io https://deemp.cachix.org' (y/N)?
+answer y.
And then, when asked
+do you want to permanently mark this value as trusted (y/N)?
+answer y again. This is to let you use the binary caches listed by the flake.
To provide binary caches, flake.nix files specify nixConfig.extra-trusted-substituters. If you try, e.g., nix develop, and Nix unsuccessfully tries to download from a cache several times, this cache has probably failed. Comment out the lines containing its URL address in extra-trusted-substituters.
Repair a derivation - manual
+Alternative steps:
+flake.nixflake.nix by . name your-corrupt-derivationpackages.default = your-corrupt-derivation in this flake.nixnix store repair .#
+.# denotes an installableSee Locales
+Templates provide extensive information about setting up development environment and packaging Haskell apps.
+ +ghcid is a Very low feature GHCi based IDE.
+It can be used to re-run a function in a given file on changes in a given directory.
+This template provides a sample configuration for this tool in the .ghcid file.
hpack translates package.yaml into .cabal.
Uses haskell4nix.
+Stack support Nix integration.
+Stack uses nix-shell.
+The name of the file providing a Nix shell can be customized in stack.yaml.
Here's the format of that file - docs.
+The shell file can import the contents of flake.nix via flake-compat.
flake.nix provides an output stack-shell.${system} = {version}: ....
stack.nix imports flake.nix and provides a shell.
devShells.default = pkgs.mkShell {
+ buildInputs = [ packageExe ];
+ shellHook = ''
+ source ${packageExe}/share/bash-completion/completions/${packageExecutableName}
+ '';
+ };
+Sometimes, HLS finds errors in code despite cabal build running successfully.
+If you use VS Code, find Outputs of Haskell Language Server and determine the cache directory for a project.
It should have approximately this form: /home/<user name>/.cache/hie-bios/dist-<project-name>-<something>.
+Remove it and restart HLS.