Merge pull request #7541 from hercules-ci/check-manual-links

Check links in the manual

6 files changed, 62 insertions, 7 deletions

diff --git a/doc/manual/book.toml b/doc/manual/book.toml
index 46ced7ff7..73fb7e75e 100644
--- a/doc/manual/book.toml
+++ b/doc/manual/book.toml
@@ -10,3 +10,12 @@ git-repository-url = "https://github.com/NixOS/nix"
 [preprocessor.anchors]
 renderers = ["html"]
 command = "jq --from-file doc/manual/anchors.jq"
+
+[output.linkcheck]
+# no Internet during the build (in the sandbox)
+follow-web-links = false
+
+# mdbook-linkcheck does not understand [foo]{#bar} style links, resulting in
+# excessive "Potential incomplete link" warnings. No other kind of warning was
+# produced at the time of writing.
+warning-policy = "ignore"
diff --git a/doc/manual/local.mk b/doc/manual/local.mk
index c0f69e00f..190f0258a 100644
--- a/doc/manual/local.mk
+++ b/doc/manual/local.mk
@@ -50,11 +50,16 @@ $(d)/src/SUMMARY.md: $(d)/src/SUMMARY.md.in $(d)/src/command-ref/new-cli
 
 $(d)/src/command-ref/new-cli: $(d)/nix.json $(d)/generate-manpage.nix $(bindir)/nix
 	@rm -rf $@
-	$(trace-gen) $(nix-eval) --write-to $@ --expr 'import doc/manual/generate-manpage.nix { toplevel = builtins.readFile $<; }'
+	$(trace-gen) $(nix-eval) --write-to $@.tmp --expr 'import doc/manual/generate-manpage.nix { toplevel = builtins.readFile $<; }'
+	# @docroot@: https://nixos.org/manual/nix/unstable/contributing/hacking.html#docroot-variable
+	$(trace-gen) sed -i $@.tmp/*.md -e 's^@docroot@^../..^g'
+	@mv $@.tmp $@
 
 $(d)/src/command-ref/conf-file.md: $(d)/conf-file.json $(d)/generate-options.nix $(d)/src/command-ref/conf-file-prefix.md $(bindir)/nix
 	@cat doc/manual/src/command-ref/conf-file-prefix.md > $@.tmp
-	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-options.nix (builtins.fromJSON (builtins.readFile $<))' >> $@.tmp
+	# @docroot@: https://nixos.org/manual/nix/unstable/contributing/hacking.html#docroot-variable
+	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-options.nix (builtins.fromJSON (builtins.readFile $<))' \
+	  | sed -e 's^@docroot@^..^g'>> $@.tmp
 	@mv $@.tmp $@
 
 $(d)/nix.json: $(bindir)/nix
@@ -67,7 +72,9 @@ $(d)/conf-file.json: $(bindir)/nix
 
 $(d)/src/language/builtins.md: $(d)/builtins.json $(d)/generate-builtins.nix $(d)/src/language/builtins-prefix.md $(bindir)/nix
 	@cat doc/manual/src/language/builtins-prefix.md > $@.tmp
-	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-builtins.nix (builtins.fromJSON (builtins.readFile $<))' >> $@.tmp
+	# @docroot@: https://nixos.org/manual/nix/unstable/contributing/hacking.html#docroot-variable
+	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-builtins.nix (builtins.fromJSON (builtins.readFile $<))' \
+	  | sed -e 's^@docroot@^..^g' >> $@.tmp
 	@cat doc/manual/src/language/builtins-suffix.md >> $@.tmp
 	@mv $@.tmp $@
 
@@ -102,6 +109,12 @@ doc/manual/generated/man1/nix3-manpages: $(d)/src/command-ref/new-cli
 	@touch $@
 
 $(docdir)/manual/index.html: $(MANUAL_SRCS) $(d)/book.toml $(d)/anchors.jq $(d)/custom.css $(d)/src/SUMMARY.md $(d)/src/command-ref/new-cli $(d)/src/command-ref/conf-file.md $(d)/src/language/builtins.md
-	$(trace-gen) RUST_LOG=warn mdbook build doc/manual -d $(DESTDIR)$(docdir)/manual
+	$(trace-gen) \
+	  set -euo pipefail; \
+	  RUST_LOG=warn mdbook build doc/manual -d $(DESTDIR)$(docdir)/manual.tmp 2>&1 \
+		  | { grep -Fv "because fragment resolution isn't implemented" || :; }
+	@rm -rf $(DESTDIR)$(docdir)/manual
+	@mv $(DESTDIR)$(docdir)/manual.tmp/html $(DESTDIR)$(docdir)/manual
+	@rm -rf $(DESTDIR)$(docdir)/manual.tmp
 
 endif
diff --git a/doc/manual/src/architecture/architecture.md b/doc/manual/src/architecture/architecture.md
index 2d1b26558..e51958052 100644
--- a/doc/manual/src/architecture/architecture.md
+++ b/doc/manual/src/architecture/architecture.md
@@ -68,7 +68,7 @@ It can also execute build plans to produce new data, which are made available to
 A build plan itself is a series of *build tasks*, together with their build inputs.
 
 > **Important**
-> A build task in Nix is called [derivation](../glossary#gloss-derivation).
+> A build task in Nix is called [derivation](../glossary.md#gloss-derivation).
 
 Each build task has a special build input executed as *build instructions* in order to perform the build.
 The result of a build task can be input to another build task.
diff --git a/doc/manual/src/command-ref/env-common.md b/doc/manual/src/command-ref/env-common.md
index 5845bdc43..bb85a6b07 100644
--- a/doc/manual/src/command-ref/env-common.md
+++ b/doc/manual/src/command-ref/env-common.md
@@ -11,7 +11,7 @@ Most Nix commands interpret the following environment variables:
     expressions using [paths](../language/values.md#type-path)
     enclosed in angle brackets (i.e., `<path>`),
     e.g. `/home/eelco/Dev:/etc/nixos`. It can be extended using the
-    [`-I` option](./opt-common#opt-I).
+    [`-I` option](./opt-common.md#opt-I).
 
   - [`NIX_IGNORE_SYMLINK_STORE`]{#env-NIX_IGNORE_SYMLINK_STORE}\
     Normally, the Nix store directory (typically `/nix/store`) is not
diff --git a/doc/manual/src/command-ref/nix-copy-closure.md b/doc/manual/src/command-ref/nix-copy-closure.md
index 83e8a2936..cd8e351bb 100644
--- a/doc/manual/src/command-ref/nix-copy-closure.md
+++ b/doc/manual/src/command-ref/nix-copy-closure.md
@@ -49,7 +49,7 @@ authentication, you can avoid typing the passphrase with `ssh-agent`.
   - `--include-outputs`\
     Also copy the outputs of [store derivation]s included in the closure.
 
-    [store derivation]: ../../glossary.md#gloss-store-derivation
+    [store derivation]: ../glossary.md#gloss-store-derivation
 
   - `--use-substitutes` / `-s`\
     Attempt to download missing paths on the target machine using Nix’s
diff --git a/doc/manual/src/contributing/hacking.md b/doc/manual/src/contributing/hacking.md
index c9da1962f..aeb0d41b3 100644
--- a/doc/manual/src/contributing/hacking.md
+++ b/doc/manual/src/contributing/hacking.md
@@ -249,3 +249,36 @@ search/replaced in it for each new build.
 The installer now supports a `--tarball-url-prefix` flag which _may_ have
 solved this need?
 -->
+
+### Checking links in the manual
+
+The build checks for broken internal links.
+This happens late in the process, so `nix build` is not suitable for iterating.
+To build the manual incrementally, run:
+
+```console
+make html -j $NIX_BUILD_CORES
+```
+
+In order to reflect changes to the [Makefile], clear all generated files before re-building:
+
+[Makefile]: https://github.com/NixOS/nix/blob/master/doc/manual/local.mk
+
+```console
+rm $(git ls-files doc/manual/ -o | grep -F '.md') && rmdir doc/manual/src/command-ref/new-cli && make html -j $NIX_BUILD_CORES
+```
+
+[`mdbook-linkcheck`] does not implement checking [URI fragments] yet.
+
+[`mdbook-linkcheck`]: https://github.com/Michael-F-Bryan/mdbook-linkcheck
+[URI fragments]: https://en.m.wikipedia.org/wiki/URI_fragment
+
+#### `@docroot@` variable
+
+`@docroot@` provides a base path for links that occur in reusable snippets or other documentation that doesn't have a base path of its own.
+
+If a broken link occurs in a snippet that was inserted into multiple generated files in different directories, use `@docroot@` to reference the `doc/manual/src` directory.
+
+If the `@docroot@` literal appears in an error message from the `mdbook-linkcheck` tool, the `@docroot@` replacement needs to be applied to the generated source file that mentions it.
+See existing `@docroot@` logic in the [Makefile].
+Regular markdown files used for the manual have a base path of their own and they can use relative paths instead of `@docroot@`.