Add missing headers to BUILD.bazel and check it in CI (#5554)

* Add missing headers to BUILD.bazel and make its generator reproduce it

The "json" cc_library did not list three headers that the library
includes:

- detail/meta/logic.hpp (added in #5016, included by from_json.hpp)
- detail/input/number_parse.hpp (added in #5283, included by lexer.hpp)
- detail/input/string_scan.hpp (added in #5283, included by lexer.hpp
  and serializer.hpp)

Bazel's sandbox only exposes declared headers, so any target depending
on @nlohmann_json//:json and including <nlohmann/json.hpp> failed with
"'nlohmann/detail/meta/logic.hpp' file not found".

The file could not simply be regenerated, because the generator behind
"make BUILD.bazel" was stale: it wrote only the "json" cc_library and
dropped the load() statements, the license block, and the
"singleheader-json" target that were added by hand in #4584. The
generator now emits the complete file, so its output differs from the
previous BUILD.bazel only by the three headers. It also resolves the
glob against the project root instead of the working directory and
sorts the list explicitly.

"make BUILD.bazel" is now phony: in a fresh checkout, BUILD.bazel is
not older than the headers, so make considered it up to date, and a
removed header would never trigger a rebuild. "make check-amalgamation"
also checks that BUILD.bazel is up to date.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Check in CI that BUILD.bazel is up to date

The "Check amalgamation" workflow now also regenerates BUILD.bazel, so a
pull request that adds, renames, or removes a header without updating
the Bazel header list fails, and the attached amalgamation.patch
contains the fix. The failure comment and the contribution guidelines
mention the new check, and the comment now links to the existing
"Amalgamate the source code" section instead of the "Files to change"
anchor that was removed in #4560.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

.github/workflows/check_amalgamation.yml

@@ -57,13 +57,16 @@ jobs:
           python3 -mvenv venv
           venv/bin/pip3 install -r $MAIN_DIR/tools/astyle/requirements.txt
 
-      - name: Regenerate amalgamation and formatting
+      - name: Regenerate amalgamation, formatting, and BUILD.bazel
         run: |
           cd $MAIN_DIR
 
           python3 $TOOL_DIR/amalgamate.py -c $TOOL_DIR/config_json.json -s .
           python3 $TOOL_DIR/amalgamate.py -c $TOOL_DIR/config_json_fwd.json -s .
 
+          # the header list of the Bazel "json" target must match the files in include/
+          cmake -P cmake/scripts/gen_bazel_build_file.cmake
+
           ${{ github.workspace }}/venv/bin/astyle --project=tools/astyle/.astylerc --suffix=none --quiet \
             $INCLUDE_DIR/json.hpp $INCLUDE_DIR/json_fwd.hpp
 
@@ -87,7 +90,7 @@ jobs:
           mkdir -p ${{ github.workspace }}/patch
           git diff --patch --no-color > ${{ github.workspace }}/patch/amalgamation.patch
           if [ -s ${{ github.workspace }}/patch/amalgamation.patch ]; then
-            echo "The source code has not been amalgamated/formatted correctly. Diff:"
+            echo "The source code has not been amalgamated/formatted correctly or BUILD.bazel is out of date. Diff:"
             cat ${{ github.workspace }}/patch/amalgamation.patch
             echo "has_diff=true" >> "$GITHUB_OUTPUT"
           else

.github/workflows/comment_check_amalgamation.yml

@@ -95,13 +95,13 @@ jobs:
               issue_number: issue_number,
               owner: context.repo.owner,
               repo: context.repo.repo,
-              body: '## 🔴 Amalgamation check failed! 🔴\nThe source code has not been amalgamated and/or formatted correctly.'
+              body: '## 🔴 Amalgamation check failed! 🔴\nThe source code has not been amalgamated and/or formatted correctly, or `BUILD.bazel` is out of date.'
                     + (hasPatch ? '\n\n📎 A ready-to-apply patch is attached to the [failed workflow run](' + runUrl + ') as the `amalgamation-patch` artifact.'
                                   + ' Download it, then apply it locally from the repository root with:'
                                   + '\n\n```shell\ngit apply amalgamation.patch\n```\n\n'
                                   + 'This does not require installing astyle yourself.'
                                 : '')
                     + (first ? '\n\n@' + author + ' Please read and follow the [Contribution Guidelines]'
-                               + '(https://github.com/nlohmann/json/blob/develop/.github/CONTRIBUTING.md#files-to-change).'
+                               + '(https://github.com/nlohmann/json/blob/develop/.github/CONTRIBUTING.md#amalgamate-the-source-code).'
                              : '')
               })