Nix: Use nixpkgs-fmt to format everything.

You can now run `nix fmt` (or `make format-changed`) to reformat Nix
files.

This is not enforced by CI.

PR-URL: hasura/graphql-engine-mono#4754
GitOrigin-RevId: a2e7cbe6c037d68ba6303278616314de60b6aa72

Makefile

@@ -3,11 +3,15 @@
 HS_FILES = $(shell git ls-files '*.hs' '*.hs-boot' | grep -v '^contrib/')
 CHANGED_HS_FILES = $(shell git diff --diff-filter=d --name-only `git merge-base HEAD origin/main` | grep '.*\(\.hs\|hs-boot\)$$' | grep -v '^contrib/')
 
+NIX_FILES = $(shell git ls-files '*.nix' 'nix/*.nix')
+
 SHELL_FILES = $(shell git ls-files '*.sh')
 CHANGED_SHELL_FILES = $(shell git diff --diff-filter=d --name-only `git merge-base HEAD origin/main` | grep '.*\.sh$$')
 
 HLINT = hlint
 
+NIX_FMT = nixpkgs-fmt
+
 ORMOLU_CHECK_VERSION = 0.3.0.0
 ORMOLU_ARGS = --cabal-default-extensions
 ORMOLU = ormolu
@@ -56,17 +60,39 @@ check-format-hs-changed: check-ormolu-version
 		$(ORMOLU) $(ORMOLU_ARGS) --mode check $(CHANGED_HS_FILES); \
 	fi
 
+# We don't bother checking only changed *.nix files, as there's so few.
+
+.PHONY: format-nix
+## format-nix: auto-format Nix source code using `nixpkgs-fmt`
+format-nix:
+	@if command -v $(NIX_FMT) > /dev/null; then \
+		echo "running $(NIX_FMT)"; \
+		$(NIX_FMT) $(NIX_FILES); \
+	else \
+		echo "$(NIX_FMT) is not installed; skipping"; \
+	fi
+
+.PHONY: check-format-nix
+## check-format-nix: check Nix source code using `nixpkgs-fmt`
+check-format-nix:
+	@if command -v $(NIX_FMT) > /dev/null; then \
+		echo "running $(NIX_FMT) --check"; \
+		$(NIX_FMT) --check $(NIX_FILES); \
+	else \
+		echo "$(NIX_FMT) is not installed; skipping"; \
+	fi
+
 .PHONY: format
-format: format-hs
+format: format-hs format-nix
 
 .PHONY: format-changed
-format-changed: format-hs-changed
+format-changed: format-hs-changed format-nix
 
 .PHONY: check-format
-check-format: check-format-hs
+check-format: check-format-hs check-format-nix
 
 .PHONY: check-format-changed
-check-format-changed: check-format-hs-changed
+check-format-changed: check-format-hs-changed check-format-nix
 
 .PHONY: lint-hs
 ## lint-hs: lint Haskell code using `hlint`
@@ -83,13 +109,13 @@ lint-hs-changed:
 	fi
 
 .PHONY: lint-shell
-## lint-shell: lint shell	scripts using `shellcheck`
+## lint-shell: lint shell scripts using `shellcheck`
 lint-shell:
 	@echo running shellcheck
 	@$(SHELLCHECK) $(SHELL_FILES)
 
 .PHONY: lint-shell-changed
-## lint-shell-changed: lint shell	scripts using `shellcheck` (changed files only)
+## lint-shell-changed: lint shell scripts using `shellcheck` (changed files only)
 lint-shell-changed:
 	@echo running shellcheck
 	@if [ -n "$(CHANGED_SHELL_FILES)" ]; then \

server/STYLE.md

@@ -9,7 +9,8 @@ existing code.
 
 We use [ormolu](https://github.com/tweag/ormolu) to format our code. The
 top-level `Makefile` has targets `format` and `check-format` that can be
-used for this.
+used for this. These targets will also format Nix files if `nixpkgs-fmt`
+is installed, but this is optional.
 
 #### Line Length
 
@@ -51,7 +52,7 @@ parseArgumentM userRoleM value = case userRoleM of
   Nothing -> ...
 ```
 
-Instead, where possible, prefer names that convey *why* the value is wrapped in
+Instead, where possible, prefer names that convey _why_ the value is wrapped in
 a `Maybe`, or, if `Nothing` is just an ordinary member of the value’s domain,
 don’t include any special indication in the name at all:
 
@@ -294,6 +295,7 @@ newtype AuthenticationToken
   -- ^ Invariant: contains Base64-encoded binary data.
   }
 ```
+
 ```haskell
 -- Good
 import Data.Text.Conversions (Base64)
@@ -303,7 +305,7 @@ newtype AuthenticationToken
   }
 ```
 
-However, *do* use comments on functions and datatypes to clarify information
+However, _do_ use comments on functions and datatypes to clarify information
 that cannot easily be communicated via names or types:
 
 ```haskell
@@ -359,6 +361,7 @@ runSelectQuery tables constraints cache shouldPrepare = do
   prepared <- if shouldPrepare then prepareQueryPlan plan else pure plan
   runQueryPlan prepared
 ```
+
 ```haskell
 runSelectQuery tables constraints cache shouldPrepare =
   constructQuery >>= executeQuery
@@ -425,6 +428,7 @@ f = (g .) . h
 ### Acknowledgement/Credits
 
 Parts of this coding style guide have been adapted from:
+
 - https://github.com/tibbe/haskell-style-guide/blob/master/haskell-style.md
 - https://kowainik.github.io/posts/2019-02-06-style-guide
 - https://chrisdone.com/posts/german-naming-convention/