docs: add a docs-review skill

.ai/skills/review-comet-docs/SKILL.md

@@ -0,0 +1,322 @@
+---
+name: review-comet-docs
+description: Use when reviewing the documentation in a DataFusion Comet pull request or branch, or when auditing an existing page or directory under docs/source or README.md. Checks wording against the documentation style guide and checks that config keys, operator names, links, images and generated content match the code. Advisory only, it never edits files or posts comments. Load alongside review-comet-pr when a PR changes docs.
+argument-hint: <pr-number | branch | docs-path>
+---
+
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+Review Comet docs: $ARGUMENTS
+
+Pick the mode from the argument:
+
+- **PR mode**: a number. Review the docs a pull request changes.
+- **Audit mode**: a file or directory that exists in the working tree. Review it as it is now.
+- **Branch mode**: a branch, tag, or commit that `git rev-parse --verify` accepts. Review what it
+  changes compared with `main`, for example before opening a PR. Otherwise, ask which one is meant.
+
+In PR mode, **REQUIRED BACKGROUND:** use `review-comet-pr` for its steps 2 to 4 (PR metadata,
+existing comments, and the diff) and its CI check. This skill only covers documentation.
+
+This skill gives advice to a human. Never edit files, commit, push, or post comments.
+
+**Shell notes.** Run every command from the repository root. Each tool call may start a new shell,
+so save the variables you set and load them again in later calls:
+
+```bash
+STATE="$(git rev-parse --git-dir)/review-comet-docs.env"
+printf 'R=%s\nHEAD_REF=%s\nBASE=%s\nADDED=%s\n' "$R" "$HEAD_REF" "$BASE" "$ADDED" > "$STATE"
+. "$STATE"
+```
+
+In zsh, `$HEAD_REF:spark/...` is read as a history modifier, so always write `"${HEAD_REF}:<path>"`.
+
+## 1. Select the Revisions
+
+Find the remote that points at `apache/datafusion-comet`, because its name differs between clones:
+
+```bash
+R=$(git remote -v | awk '/apache\/datafusion-comet(\.git)? \(fetch\)/ {print $1; exit}')
+```
+
+If `R` is empty, use `https://github.com/apache/datafusion-comet.git` in its place.
+
+**PR mode.** Read the base branch and changed files, then fetch the base and the head without
+touching the working tree. The leading `+` lets the fetch replace a ref after a force push.
+
+```bash
+gh pr view <pr> --repo apache/datafusion-comet --json baseRefName,headRefOid,files
+git fetch "$R" "+refs/heads/<base>:refs/review/base-<pr>" "+pull/<pr>/head:refs/review/pr-<pr>"
+HEAD_REF=refs/review/pr-<pr>; BASE=$(git merge-base refs/review/base-<pr> "$HEAD_REF")
+```
+
+Check that `git rev-parse "$HEAD_REF"` equals `headRefOid`. If it does not, the PR changed while you
+fetched it: run both commands again, at most twice.
+
+**Branch mode.** Fetch `main` the same way, then compare with it:
+
+```bash
+git fetch "$R" "+refs/heads/main:refs/review/main"
+HEAD_REF=<branch>; BASE=$(git merge-base refs/review/main "$HEAD_REF")
+```
+
+**Audit mode.** There is no base. List the files, including new files that are not committed yet,
+and search them with `--untracked`:
+
+```bash
+git ls-files --cached --others --exclude-standard -- <path>
+```
+
+In PR and branch mode, read every file, including linked pages and the code a claim describes, from
+`$HEAD_REF`. If `git rev-list --count "$BASE"..refs/review/base-<pr>` (or `..refs/review/main`) is
+not zero, `main` has moved since the change branched. Check the claims against `main` too, and report
+what has changed there.
+
+## 2. Read the Style Guide
+
+Read `docs/source/contributor-guide/style_guide.md` in full on every run. If the change edits the
+guide, read its version with `git show "${HEAD_REF}:docs/source/contributor-guide/style_guide.md"`.
+Otherwise, read it from the working tree. If the file does not exist, stop and say so.
+
+The guide is the rulebook, and its first section says what it covers. Cite its rule IDs (`T3`, `N1`,
+`P16`, and so on), and do not restate or reinterpret its rules here. If the guide and this skill
+disagree, the guide wins.
+
+## 3. Select the Files
+
+In PR and branch mode, `<paths>` below means these changed files:
+
+- `.md` and `.rst` files under `docs/source`, and `README.md`;
+- files that change `.doc(...)` strings in `CometConf.scala` or in contrib config classes;
+- files that change doc comments (Scaladoc, Javadoc, and Rust `///` comments);
+- `AGENTS.md` and `.ai/skills/**/SKILL.md`.
+
+For doc comments, `AGENTS.md`, and skills, check the vocabulary and accuracy rules the guide names
+for them, not the page conventions. Check the changed lines and the paragraphs around them, not the
+whole page. Report a problem in unchanged text only when the change makes it wrong, or list it
+separately as already on the page. Also read the code diff for the behavior the changed docs
+describe, because docs are usually only as accurate as the code change beside them.
+
+In every mode:
+
+- Skip the content the guide's **Generated Content** section lists as generated or as records.
+  Review the hand-written text around the generated markers. Text between the markers that differs
+  from what `GenerateDocs` produces is a hand edit, and a finding (`P5`).
+- Do the judgment checks in step 5 for at most 10 pages per run. List any pages you skipped so the
+  user can run the skill again on them.
+
+## 4. Mechanical Checks
+
+These checks produce candidates, not findings. Read each hit in context before reporting it. For the
+wording checks, ignore hits inside fenced code blocks, inline code, quoted plan output or logs, and
+text that quotes a phrase in order to discuss it (`N6`), such as the style guide's own examples. The
+accuracy checks still apply to code font: config keys, operator names, and code examples are usually
+written that way. For each check, record what it checked, the number of hits, and how many of them
+are findings.
+
+Use `git grep -P` or `perl`, as written. The system `grep` on macOS has no `-P`, and `git grep -E`
+does not support `\b`, so it silently finds nothing. Plain `\b` also misses Markdown italics such as
+`_native execution_`, because `_` counts as a word character, so the patterns below use lookarounds.
+
+**Lines to check.** In PR and branch mode, list the added lines with their file and line number, and
+run the line checks below on this list only. In audit mode, run the line checks on the files with
+`git grep -n --untracked`.
+
+```bash
+ADDED=$(mktemp "$(git rev-parse --git-dir)/review-added.XXXXXX")
+git diff --no-ext-diff --src-prefix=a/ --dst-prefix=b/ -U0 "$BASE" "$HEAD_REF" -- <paths> \
+  | awk '/^--- /{h=1; next}
+         h && /^\+\+\+ b\//{f=substr($0,7); sub(/\t$/,"",f); h=0; next}
+         /^@@/{h=0; split($3,a,/[+,]/); n=a[2]; next}
+         /^\+/{print f":"n": "substr($0,2); n++}' > "$ADDED"
+```
+
+**"Native" and "vectorized".** Check each hit against `N1`-`N6` and `T10`. Which page the hit is on
+matters, because `N3` allows more in the contributor guide:
+
+```bash
+perl -ne 'print if /^.+?:\d+: .*(?:(?<![A-Za-z0-9])native(?:ly)?(?![A-Za-z0-9])|vectori[sz]ed)/i' "$ADDED"
+git grep -n -i --untracked -P '(?<![A-Za-z0-9])native(ly)?(?![A-Za-z0-9])|vectori[sz]ed' -- <files>   # audit
+```
+
+**Config keys.** Every `spark.comet.*` key a page names must exist (`P13`). List the keys the text
+names, then the keys the code defines at the revision under review. `<rev>` is `$HEAD_REF`, or
+nothing in audit mode. The second command reads definitions that span two lines, expands
+`createExecEnabledConfig`, and leaves out deprecated alternative names and unexpanded templates:
+
+```bash
+perl -ne 'print "$1\n" while /(spark\.comet\.[\w.<>]*[\w>])/g' "$ADDED" | sort -u
+git grep -h -A1 -P '\b(conf|ConfigBuilder|createExecEnabledConfig)\(' <rev> -- spark/src/main contrib \
+  | perl -0777 -ne '
+      while (/\b(?:conf|ConfigBuilder)\(\s*s?"([^"]+)"/g) {
+        ($k = $1) =~ s/\$\{?COMET_EXEC_CONFIG_PREFIX\}?/spark.comet.exec/;
+        $k =~ s/\$\{?COMET_PREFIX\}?/spark.comet/;
+        print "$k\n" if $k =~ /^spark\.comet\./ && $k !~ /\$/;
+      }
+      while (/\bcreateExecEnabledConfig\(\s*"([^"]+)"/g) { print "spark.comet.exec.$1.enabled\n" }' \
+  | sort -u
+```
+
+If the second command prints nothing, it is broken: stop and report that, rather than flagging every
+key. Some keys are built from a name at run time:
+
+- `spark.comet.expression.<Name>.enabled` and `.allowIncompatible`: `<Name>` is the Spark expression
+  class name, as in the `QueryPlanSerde` serde maps, not a Comet or protobuf name. Some expressions
+  use their own opt-in key instead, set by `nativeOptInConfigKeyOverride`, such as
+  `spark.comet.caseConversion.enabled`.
+- `spark.comet.operator.<Name>.allowIncompatible`: `<Name>` is the Spark operator class name, such as
+  `ProjectExec`.
+- `spark.comet.datafusion.<key>`: not a Comet config. Comet passes it to DataFusion only when
+  `spark.comet.exec.respectDataFusionConfigs=true`, which is off by default. Check the key against
+  DataFusion.
+
+Before reporting a missing key, search the code for it, because a few keys are defined in other
+ways, such as `spark.comet.version` in `Plugins.scala`. A deprecated key that a page still uses is a
+finding (`P16`).
+
+**Operator names.** Check operator names against `O1`, class names against `O2`, and expressions
+against `O4`. List the concrete operator classes and the classes that override their printed name:
+
+```bash
+git grep -h -o -P 'case class (Comet|Iceberg)[A-Za-z]+Exec\b' <rev> -- spark/src/main contrib | sort -u
+git grep -n -P 'override (def|val|lazy val) (nodeName|simpleString)' <rev> -- spark/src/main contrib
+```
+
+`spark/src/main` includes the per-Spark-version source directories. If the first command prints
+nothing, it is broken: stop and report that. A class's `nodeName` is its name without `Exec`, unless
+it overrides `nodeName`. Compare each name in the text with these, as `O1` describes, not with a rule
+about suffixes. When the page is an operator reference, also report concrete operators that it
+leaves out. Leave out planning markers such as `CometScanExec`, which never appear in a final plan,
+and contrib operators, which belong on their contrib page.
+
+**Links and images.** For each link or image in the text, inline or reference-style
+(`[text]: target`):
+
+- A Markdown link or image path under `docs/source` is relative to the page, or to `docs/source` when
+  it starts with `/`. Check that the file exists at the revision under review. A raw HTML link to a
+  `.html` page, or a link with no extension, refers to the `.md` or `.rst` source of the same name.
+- An `#anchor` must match a target on that page: an explicit label, or a heading slug. MyST makes
+  slugs for H1-H4 headings by lowercasing the text, turning each space into `-`, and removing
+  everything except letters, digits, `_`, and `-`. A repeated heading gets a numbered suffix.
+- A link to Comet's published docs by URL breaks `P4` on pages under `docs/source`, but not in
+  `README.md`.
+- For external links on the lines under review (at most 20 in audit mode), check the status with
+  `curl -s -o /dev/null -w '%{http_code}' -I -L --max-time 10 <url>`. Report a 404 as a finding. If
+  the request fails or the network is unavailable, say the link was not checked.
+
+**Structure.** Check for one H1 and no skipped heading levels (`P2`), the ASF header on new files
+(`P1`), and new pages missing from a toctree (`P6`). The heading command skips fenced code, where
+`#` starts a shell comment. Read the file with `git show "${HEAD_REF}:<file>"`, or from the working
+tree in audit mode:
+
+````bash
+git show "${HEAD_REF}:<file>" | awk '/^[[:space:]]*(```|~~~)/{f=!f; next} !f && /^#{1,6} /{print FNR": "$0}'
+git grep -n '<page-name>' <rev> -- 'docs/source/*.md' 'docs/source/*.rst'
+````
+
+For the toctree check, search for the page's file name without `.md`. The pathspec matches every page,
+including `docs/source/index.md`. A hit counts only inside a `{toctree}` block or a `.. toctree::`
+directive, not in an ordinary link.
+
+**Moved and removed pages.** In PR and branch mode, list the pages the change renames or deletes.
+Each one needs an entry in `redirects` in `docs/source/conf.py` (`P17`):
+
+```bash
+git diff --name-status --diff-filter=DR "$BASE" "$HEAD_REF" -- docs/source
+```
+
+**Version claims and markers.** Find version claims to check against `P8`, and `TODO` or `XXX`
+markers, which break `P7`:
+
+```bash
+perl -ne 'print if /^.+?:\d+: .*(?:(?:Spark|Iceberg) [0-9]\.[0-9x]+\+?|\b(?:TODO|XXX)\b)/' "$ADDED"
+git grep -n --untracked -P '(Spark|Iceberg) [0-9]\.[0-9x]+\+?|\b(TODO|XXX)\b' -- <files>   # audit
+```
+
+CI runs prettier and the Apache RAT license check on PRs, so do not repeat them. If CI has not run
+them yet, for example on a draft, say they were not checked. Mention them otherwise only when CI has
+failed on them.
+
+## 5. Judgment Checks
+
+- **Is it true?** For every sentence that names a class, rule, config, default, or file, read the
+  code it describes at the revision under review. A sentence can follow every wording rule and
+  still be wrong: a scan that no longer exists, a config default that has changed, or an operator
+  described as Rust-implemented that runs on the JVM. Check numbers, versions, and names first, and
+  check that a condition in the text is the whole condition in the code. Pages that describe
+  architecture or test infrastructure go stale most often. A false or outdated claim breaks `P16`.
+  This is the most valuable check in this skill.
+- **Does it agree with the rest of the docs?** A new sentence can contradict an older one on the
+  same page, or a count such as "five configs" can stop matching the list below it (`P16`). When a
+  change rewrites the description of a config or class, search `docs/source` for the same name and
+  check the other descriptions.
+- **Which axis?** When you suggest a replacement for vague "native", choose the term the code
+  supports: _in the Comet pipeline_ (`T1`), _Rust-implemented_ (`T3`), or _JVM-side_ (`T4`). Never
+  suggest _Rust-implemented_ without checking the code.
+- **Page conventions.** Check `P3`, `P7`, `P8`, `P9`, `P10`, `P11`, `P12`, `P14`, and `P18` by
+  reading the page. For plan output (`P12`, `P16`), check that the operator names exist, that the
+  tree shape is one Spark could print, and that messages in it match the strings in the code. Do not
+  ask for new plan output to be invented.
+- **Same-change updates.** If the change adds an operator or expression, check the pages `P15`
+  lists. If it adds a config, check that its `.doc(...)` string follows the guide, since
+  `GenerateDocs` publishes it, and that any page that documents the config by hand mentions it.
+
+## 6. Severity
+
+- **Must-fix.** The page is wrong or broken: a false or outdated claim (`P16`), a config key, class,
+  or file that does not exist (`P13`), a broken link, anchor, or image, a hand edit to generated
+  content, a new file without the ASF header, or a new page missing from a toctree. When a sentence
+  is both false and badly worded, report it once, as must-fix, with a rewrite that fixes both.
+- **Should-fix.** The page breaks a style guide rule, but what it says is true. Most `T`, `N`, `O`,
+  and `P` findings belong here.
+- **Nit.** A one-off change that would make the text clearer, but that no rule requires. Nits carry
+  no rule ID.
+
+A problem that keeps coming up and that no rule covers is a **guide gap**, not a finding. Report it
+so the guide can be extended.
+
+## 7. Output
+
+When this skill runs as part of a `review-comet-pr` review, put its findings into that skill's
+**Findings** and **Suggested Review Comments**, and drop the nits. That skill's review bar has no
+third tier, and its rules win for anything posted to a PR. On its own, use this format:
+
+1. **Scope.** The mode, the revisions reviewed (the base and head commits, and which guide version),
+   the files reviewed, and the files skipped, with the reason.
+2. **Mechanical checks.** A table with each check, its hit count, and how many hits are findings.
+3. **Findings**, grouped as must-fix, should-fix, and nit. For each one give the `path:line`, the
+   rule ID, the text quoted from the page, and a suggested rewrite. Keep rewrites short and plain,
+   and change only what the rule requires.
+4. **Guide gaps.**
+
+If there are no findings, say so.
+
+## Checking This Skill
+
+After changing this skill or the style guide, run it on these cases and compare the results. The
+expected results were checked on `main` in October 2026, so a later fix to a page can change them.
+
+| Run                                                                | Expected                                                                                                                         |
+| ------------------------------------------------------------------ | -------------------------------------------------------------------------------------------------------------------------------- |
+| PR mode on #6786                                                   | Must-fix: `datasources.md` and the new `.doc` string claim more than `shouldBridgeUnsupportedScan` does                          |
+| Audit `docs/source/user-guide/latest/understanding-comet-plans.md` | No finding for Comet's _native shuffle_, `CometNativeScan`, `CometWindowExec`, or config keys; `N5` for "Spark's native shuffle" |
+| Audit `docs/source/contributor-guide/timezones.md`                 | No finding for _native code_ or _native plan_, or for `ToJson` and `ToCsv`, which are protobuf message names                     |
+| Audit `docs/source/user-guide/latest/compatibility/expressions`    | Lists all 16 files, reviews 10 of the templates and index pages, names the skipped ones, and skips only text between markers     |
+| Audit a scratch page containing `_native execution_`               | `N1` finding                                                                                                                     |

.ai/skills/review-comet-expression-pr/SKILL.md

@@ -225,9 +225,10 @@ and the requirement to record a performance audit. Hold the PR to both.
 
 ### Generated, review the source instead
 
-The compatibility pages under `docs/source/user-guide/latest/compatibility/expressions/` and
-`docs/source/user-guide/latest/configs.md` are produced by `GenerateDocs` and regenerated by CI on
-merge. Never ask the contributor to hand-edit them. Check what feeds them:
+`GenerateDocs` fills in the expression compatibility tables and the config tables when the docs are
+built, and CI rebuilds and publishes the docs when a merge changes their inputs. The **Generated Content** section of
+`docs/source/contributor-guide/style_guide.md` says exactly which text is generated. Never ask the
+contributor to hand-edit that text. Check what feeds it:
 
 - Expression marked `Incompatible(Some("..."))` but `getIncompatibleReasons()` is empty, so the
   compat page shows it as supported with no caveats.