Format Markdown with prettier in make fmt (closes #43)

script/fmt and script/fmt-check now run prettier on every Markdown file
after their Go steps, as the standard scripts from sneak/prompts at
dd4027b do. script/bootstrap gains the standard node, nvm and yarn
install next to its goimports install, and the last Dockerfile stage
copies package.json and yarn.lock before running it. .prettierrc,
.prettierignore and yarn.lock are the standard copies. package.json is
the standard one without its licence field and marked private, because
this repo's licence is the WTFPL. .dockerignore keeps the log of a failed
yarn install out of the build context. README.md and TODO.md are
reformatted once with it; REPO_POLICIES.md already matched.

Model: opus-5-5

.dockerignore

@@ -72,10 +72,12 @@
 **/*.sublime-*
 
 # This repository's host-built artifacts: the example program's binary,
-# test binaries and coverage output.
+# test binaries, coverage output, and the log yarn writes when an install
+# fails.
 /cmd/example/example
 /*.test
 /*.out
+/yarn-error.log
 
 # aider's files, among them a config file that can hold an API key.
 **/.aider*

.prettierignore

@@ -0,0 +1,2 @@
+node_modules/
+yarn.lock

.prettierrc

@@ -0,0 +1,4 @@
+{
+    "tabWidth": 4,
+    "proseWrap": "always"
+}

Dockerfile

@@ -31,6 +31,6 @@ COPY --from=lint /src/go.sum /dev/null
 COPY --from=test /src/go.sum /dev/null
 WORKDIR /src
 COPY script/ script/
-COPY go.mod go.sum ./
+COPY go.mod go.sum package.json yarn.lock ./
 RUN script/bootstrap
 COPY . .

README.md

@@ -3,11 +3,10 @@
 ## Summary
 
 simplelog is an opinionated logging package designed to facilitate easy and
-structured logging in Go applications with an absolute minimum of
-boilerplate.
+structured logging in Go applications with an absolute minimum of boilerplate.
 
-The idea is that you can add a single import line which replaces the
-stdlib `log/slog` default handler, and solve the 90% case for logging.
+The idea is that you can add a single import line which replaces the stdlib
+`log/slog` default handler, and solve the 90% case for logging.
 
 ## Current Status
 
@@ -18,16 +17,15 @@ Released v1.0.0 2024-06-14.  Works as intended.  No known bugs.
 - if output is a tty, outputs pretty color logs
 - if output is not a tty, outputs json
 - supports delivering each log message via a webhook
--   emits every `slog` attribute: those passed to a log call, those
-    accumulated with `WithAttrs`, and those qualified by `WithGroup`.
-    `slog.Group` values nest, and `slog.LogValuer` values are resolved. In
-    json output attributes are object fields (groups become nested objects);
-    in console output they are appended as `key=value` pairs, with grouped
-    keys written as `group.key=value`. See
-    [Attribute output](#attribute-output) for the details worth knowing
--   reports a record that could not be delivered as an error from the
-    handler's `Handle` method. See
-    [When delivery fails](#when-delivery-fails) for how to receive it
+- emits every `slog` attribute: those passed to a log call, those accumulated
+  with `WithAttrs`, and those qualified by `WithGroup`. `slog.Group` values
+  nest, and `slog.LogValuer` values are resolved. In json output attributes are
+  object fields (groups become nested objects); in console output they are
+  appended as `key=value` pairs, with grouped keys written as `group.key=value`.
+  See [Attribute output](#attribute-output) for the details worth knowing
+- reports a record that could not be delivered as an error from the handler's
+  `Handle` method. See [When delivery fails](#when-delivery-fails) for how to
+  receive it
 
 ## Planned Features
 
@@ -49,9 +47,9 @@ go get sneak.berlin/go/simplelog
 
 ## Usage
 
-Below is an example of how to use SimpleLog in a Go application. This
-example is provided in the form of a `main.go` file, which demonstrates
-logging at various levels using structured logging syntax.
+Below is an example of how to use SimpleLog in a Go application. This example is
+provided in the form of a `main.go` file, which demonstrates logging at various
+levels using structured logging syntax.
 
 ```go
 package main
@@ -73,63 +71,58 @@ func main() {
 ## Attribute output
 
 Attributes reach every handler: the ones passed to the log call, the ones
-accumulated with `WithAttrs`, and the ones qualified by the groups open at
-the time they were attached. `slog.Group` values nest, and
-`slog.LogValuer` values are resolved to the value they stand for. A few
-behaviours are worth knowing before you rely on them.
+accumulated with `WithAttrs`, and the ones qualified by the groups open at the
+time they were attached. `slog.Group` values nest, and `slog.LogValuer` values
+are resolved to the value they stand for. A few behaviours are worth knowing
+before you rely on them.
 
-**Your values are never modified.** Whatever you log is read and rendered,
-never written to. A map or a slice you pass to `slog.Any` comes back from
-the logger exactly as you handed it over, even when a group later uses the
-same key.
+**Your values are never modified.** Whatever you log is read and rendered, never
+written to. A map or a slice you pass to `slog.Any` comes back from the logger
+exactly as you handed it over, even when a group later uses the same key.
 
-**Durations are nanoseconds in json, and readable on the console.** The
-json and webhook payloads emit a `slog.Duration` as a number of
-nanoseconds, matching `slog.NewJSONHandler`, so a consumer can compare and
-aggregate the field without parsing it. The console line emits the same
-duration as `3s`, matching `slog.NewTextHandler`, because a person reads
-it.
+**Durations are nanoseconds in json, and readable on the console.** The json and
+webhook payloads emit a `slog.Duration` as a number of nanoseconds, matching
+`slog.NewJSONHandler`, so a consumer can compare and aggregate the field without
+parsing it. The console line emits the same duration as `3s`, matching
+`slog.NewTextHandler`, because a person reads it.
 
-**The json payload is an object, with the consequences an object has.**
-The record's own fields are named `Time`, `Level`, `Message` and `PC`, and
-they own those names: an attribute keyed after one of them is dropped from
-the json and webhook output. A key logged more than once keeps its last
-value there for the same reason, with one exception: when both are
-`slog.Group` values sharing a key, the two groups are merged into one
-object holding the members of both, rather than the second replacing the
-first. Neither the collision nor the merge applies to the console output,
-which is a line of text: every pair appears, in order. If you need a field
-called `message`, pick a key that does not collide - the collision is
-silent.
+**The json payload is an object, with the consequences an object has.** The
+record's own fields are named `Time`, `Level`, `Message` and `PC`, and they own
+those names: an attribute keyed after one of them is dropped from the json and
+webhook output. A key logged more than once keeps its last value there for the
+same reason, with one exception: when both are `slog.Group` values sharing a
+key, the two groups are merged into one object holding the members of both,
+rather than the second replacing the first. Neither the collision nor the merge
+applies to the console output, which is a line of text: every pair appears, in
+order. If you need a field called `message`, pick a key that does not collide -
+the collision is silent.
 
-**Empty things follow the `slog.Handler` contract.** An empty `Attr` is
-ignored, an empty group is elided along with its key, a group with an
-empty key is inlined into its parent, and `WithGroup("")` returns the
-handler unchanged.
+**Empty things follow the `slog.Handler` contract.** An empty `Attr` is ignored,
+an empty group is elided along with its key, a group with an empty key is
+inlined into its parent, and `WithGroup("")` returns the handler unchanged.
 
 ## When delivery fails
 
-Every handler returns an error from `Handle` when it could not deliver
-the record:
+Every handler returns an error from `Handle` when it could not deliver the
+record:
 
 - `ConsoleHandler` and `JSONHandler` return the error from their write to
   stdout, wrapped, so `errors.Is` still matches the original
--   `WebhookHandler` returns an error when the request fails, and also when
-    the server answers with a status outside 2xx, a redirect included,
-    since it does not follow redirects. A request that has not finished
-    after 5 seconds fails with a timeout error, so a webhook server that
-    never answers holds up a log call for 5 seconds at most
--   `MultiplexHandler`, which simplelog installs as the default, passes the
-    record to every handler it holds even after one of them fails, then
-    returns all their errors joined with `errors.Join` (nil if none failed)
+- `WebhookHandler` returns an error when the request fails, and also when the
+  server answers with a status outside 2xx, a redirect included, since it does
+  not follow redirects. A request that has not finished after 5 seconds fails
+  with a timeout error, so a webhook server that never answers holds up a log
+  call for 5 seconds at most
+- `MultiplexHandler`, which simplelog installs as the default, passes the record
+  to every handler it holds even after one of them fails, then returns all their
+  errors joined with `errors.Join` (nil if none failed)
 
-`slog.Info`, `slog.Error` and the other `slog.Logger` methods throw that
-error away. That is how `log/slog` works, and simplelog cannot change it.
-To find out whether a record was delivered, build a `slog.Record` and pass
-it to the handler yourself, for example
-`slog.Default().Handler().Handle(ctx, record)`, then check the error it
-returns. Console output takes the file and line from the record's `PC`,
-which you set with `runtime.Callers` as the `log/slog` documentation
+`slog.Info`, `slog.Error` and the other `slog.Logger` methods throw that error
+away. That is how `log/slog` works, and simplelog cannot change it. To find out
+whether a record was delivered, build a `slog.Record` and pass it to the handler
+yourself, for example `slog.Default().Handler().Handle(ctx, record)`, then check
+the error it returns. Console output takes the file and line from the record's
+`PC`, which you set with `runtime.Callers` as the `log/slog` documentation
 shows. A record whose `PC` is zero prints `???:0` instead.
 
 ## Entrypoints
@@ -143,8 +136,10 @@ alpine. We provide:
 
 - `script/bootstrap` — install all dependencies (go if missing, goimports with
   `go install` at a pinned commit unless the installed one already reports the
-  pinned version, then `go mod download`); golangci-lint is not installed,
-  since it runs only in Docker
+  pinned version, then `go mod download`; node through nvm at a pinned version
+  if node is missing, yarn at a pinned version if it is missing, then the
+  `prettier` that `package.json` and `yarn.lock` pin); golangci-lint is not
+  installed, since it runs only in Docker
 - `script/setup` — set up the repo for development after a fresh clone: runs
   `script/bootstrap`, then `script/install-precommit`
 - `script/projectname` — output the project name (our own extension); used by
@@ -152,23 +147,23 @@ alpine. We provide:
 - `script/test` — run the test suite under the race detector in Docker by
   building only the `test` stage of the `Dockerfile`, without the build cache,
   so every run tests; the image is tagged `simplelog-test`
-- `script/lint` — run golangci-lint in Docker by building only the `lint`
-  stage of the `Dockerfile`, without the build cache, so every run lints; the
-  image is tagged `simplelog-lint`
-- `script/fmt` — format all files (writes) with the goimports that
-  `script/bootstrap` installs
-- `script/fmt-check` — check formatting (read-only); fails if `gofmt -l`
-  reports files
+- `script/lint` — run golangci-lint in Docker by building only the `lint` stage
+  of the `Dockerfile`, without the build cache, so every run lints; the image is
+  tagged `simplelog-lint`
+- `script/fmt` — format all files (writes): Go with the goimports that
+  `script/bootstrap` installs, then every `*.md` file with `prettier`
+- `script/fmt-check` — check formatting (read-only); fails if `gofmt -l` reports
+  files, or if `prettier` would change any `*.md` file
 - `script/check` — run all checks: `test`, `lint`, `fmt-check` (our own
   extension)
-- `script/docker` — build the Docker image without the build cache, tagged
-  via `script/projectname` (byte-identical across repos); it also passes the
-  output of `git describe` as the `VERSION` build argument, which is ignored
-  because this `Dockerfile` does not declare it
-- `script/cibuild` — what CI runs: `script/bootstrap`, then `script/check`,
-  then the same image build as `script/docker` (byte-identical across repos)
-- `script/precommit` — run by the git pre-commit hook (our own extension);
-  runs a `go mod tidy` guard, then `script/check`
+- `script/docker` — build the Docker image without the build cache, tagged via
+  `script/projectname` (byte-identical across repos); it also passes the output
+  of `git describe` as the `VERSION` build argument, which is ignored because
+  this `Dockerfile` does not declare it
+- `script/cibuild` — what CI runs: `script/bootstrap`, then `script/check`, then
+  the same image build as `script/docker` (byte-identical across repos)
+- `script/precommit` — run by the git pre-commit hook (our own extension); runs
+  a `go mod tidy` guard, then `script/check`
 - `script/install-precommit` — installs the git pre-commit hook (our own
   extension); `make hooks` shims to it
 

TODO.md

@@ -1,86 +1,89 @@
 # Workflow
 
-* branch (from `main`)
-* do the work in Next Step
-* move Next Step to the top of Completed Steps
-* move the top item of Future Steps into Next Step
-* commit (`TODO.md` changes in the same commit as the work)
-* merge to `main` if the branch is not protected, otherwise open a PR
-* push
+- branch (from `main`)
+- do the work in Next Step
+- move Next Step to the top of Completed Steps
+- move the top item of Future Steps into Next Step
+- commit (`TODO.md` changes in the same commit as the work)
+- merge to `main` if the branch is not protected, otherwise open a PR
+- push
 
 # Status
 
 1.0+
 
-Tagged v1.0.0 (2024-06-14) and 1.0.1 (2026-02-08). In post-1.0
-maintenance; the library is referenced by the Go styleguide.
+Tagged v1.0.0 (2024-06-14) and 1.0.1 (2026-02-08). In post-1.0 maintenance; the
+library is referenced by the Go styleguide.
 
 # Next Step
 
-Restructure README.md into the standard sections: Description, Getting
-Started, Rationale, Design, TODO, License, Author
+Restructure README.md into the standard sections: Description, Getting Started,
+Rationale, Design, TODO, License, Author
 
 # Completed Steps
 
-* 2026-10-06: re-vendored the standard files from `sneak/prompts` at
-    commit `dd4027b`: `REPO_POLICIES.md`, the CI workflow, `.gitignore`,
-    and `.golangci.yml` together with the lint stage's new image, plus
-    the `.editorconfig` and `.dockerignore` this repo lacked, which
-    finishes the Makefile and policy-files step. `script/cibuild` now
-    bootstraps and runs `script/check` before building the image, the
-    format check runs only on the host, the last `Dockerfile` stage runs
-    `script/bootstrap`, which installs goimports at a pinned commit
-* 2026-10-06: a webhook request now times out after 5 seconds, so a
-    server that never answers no longer stops every log call; the webhook
-    handler also reads each answer to the end so its connection is reused
-* 2026-10-06: the console handler takes the file and line it prints from
-    the record's `PC` instead of counting stack frames, so they name the
-    call site whether the record came through a `slog.Logger` or straight
-    to `Handle`
-* 2026-10-06: the tests run under the race detector, in Docker:
-    `script/test` builds the `test` stage of the `Dockerfile`, which runs
-    `go test -race`, and a new final stage makes a plain `docker build`
-    run both the `lint` and `test` stages
-* 2026-10-06: the linter runs only in Docker: `script/lint` builds the
-    `lint` stage of the `Dockerfile`, every `docker build` in `script/`
-    runs without the build cache, and `script/bootstrap` no longer
-    installs golangci-lint
-* 2026-10-06: every handler now returns a failed delivery from `Handle`
-    instead of discarding it: console and JSON return the stdout write
-    error, the webhook also fails on a non-2xx answer, and the multiplex
-    delivers to every handler and returns their errors joined
-* 2026-08-10: fixed every handler discarding slog attributes: console,
-    JSON and webhook handlers now emit record attributes, accumulate
-    WithAttrs without mutating the receiver, and honour WithGroup;
-    slog.Group values nest and LogValuer values are resolved; console
-    keys and values holding invalid UTF-8 are quoted
-* 2026-08-07: added canonical `.golangci.yml` (v2 schema), pinned the
-    `Dockerfile` lint stage to golangci-lint v2.12.2 (tag+digest), and
-    fixed all findings the v1→v2 jump surfaced without changing any
-    exported signatures or behavior
-- 2026-07-07 Adopted scripts-to-rule-them-all: `script/` entrypoints,
-    Makefile shims, README Entrypoints section
-* 2026-02-08: fixed JSONHandler deadlock from recursive log.Println,
-    with regression test; tagged 1.0.1
-* 2024-06-14: 1.0 prep: lint and fmt enforced in Docker build, call
-    stack depth fix so log locations report correctly, example script,
-    removed non-building RELP code; tagged v1.0.0
-* 2024-05-22: module path moved to sneak.berlin/go/simplelog
-* 2024-05-14: initial library: slog-based console, JSON, webhook, and
-    RELP handlers, MultiplexHandler, caller file/line info, UTC ISO
-    timestamps, level-colored output
+- 2026-10-06: `make fmt` and `make fmt-check` also format Markdown, with
+  `prettier` at the standard settings, pinned through `package.json` and
+  `yarn.lock`; `script/bootstrap` installs node and yarn for it, and the
+  existing Markdown was formatted once
+- 2026-10-06: re-vendored the standard files from `sneak/prompts` at commit
+  `dd4027b`: `REPO_POLICIES.md`, the CI workflow, `.gitignore`, and
+  `.golangci.yml` together with the lint stage's new image, plus the
+  `.editorconfig` and `.dockerignore` this repo lacked, which finishes the
+  Makefile and policy-files step. `script/cibuild` now bootstraps and runs
+  `script/check` before building the image, the format check runs only on the
+  host, the last `Dockerfile` stage runs `script/bootstrap`, which installs
+  goimports at a pinned commit
+- 2026-10-06: a webhook request now times out after 5 seconds, so a server that
+  never answers no longer stops every log call; the webhook handler also reads
+  each answer to the end so its connection is reused
+- 2026-10-06: the console handler takes the file and line it prints from the
+  record's `PC` instead of counting stack frames, so they name the call site
+  whether the record came through a `slog.Logger` or straight to `Handle`
+- 2026-10-06: the tests run under the race detector, in Docker: `script/test`
+  builds the `test` stage of the `Dockerfile`, which runs `go test -race`, and a
+  new final stage makes a plain `docker build` run both the `lint` and `test`
+  stages
+- 2026-10-06: the linter runs only in Docker: `script/lint` builds the `lint`
+  stage of the `Dockerfile`, every `docker build` in `script/` runs without the
+  build cache, and `script/bootstrap` no longer installs golangci-lint
+- 2026-10-06: every handler now returns a failed delivery from `Handle` instead
+  of discarding it: console and JSON return the stdout write error, the webhook
+  also fails on a non-2xx answer, and the multiplex delivers to every handler
+  and returns their errors joined
+- 2026-08-10: fixed every handler discarding slog attributes: console, JSON and
+  webhook handlers now emit record attributes, accumulate WithAttrs without
+  mutating the receiver, and honour WithGroup; slog.Group values nest and
+  LogValuer values are resolved; console keys and values holding invalid UTF-8
+  are quoted
+- 2026-08-07: added canonical `.golangci.yml` (v2 schema), pinned the
+  `Dockerfile` lint stage to golangci-lint v2.12.2 (tag+digest), and fixed all
+  findings the v1→v2 jump surfaced without changing any exported signatures or
+  behavior
+
+* 2026-07-07 Adopted scripts-to-rule-them-all: `script/` entrypoints, Makefile
+  shims, README Entrypoints section
+
+- 2026-02-08: fixed JSONHandler deadlock from recursive log.Println, with
+  regression test; tagged 1.0.1
+- 2024-06-14: 1.0 prep: lint and fmt enforced in Docker build, call stack depth
+  fix so log locations report correctly, example script, removed non-building
+  RELP code; tagged v1.0.0
+- 2024-05-22: module path moved to sneak.berlin/go/simplelog
+- 2024-05-14: initial library: slog-based console, JSON, webhook, and RELP
+  handlers, MultiplexHandler, caller file/line info, UTC ISO timestamps,
+  level-colored output
 
 # Future Steps
 
-* Delete the old plain TODO file once this TODO.md lands
-* Add .aider.* to .gitignore and remove the stray aider artifacts from
-    the working tree
-* Pick one tag scheme before the next release (v1.0.0 vs 1.0.1 are
-    inconsistent)
-* Tag v1.0.2, with the leading v, once the attribute fix lands, so
-    consuming repos can move off pseudo-version pins in one step
-* Fix RELP output to cache (from old TODO)
-* Re-add RELP delivery over TCP to remote rsyslog imrelp; removed
-    2024-06-14 because it did not build (README planned feature)
-* Add regex filtering for webhook logs (from old TODO)
-* Better console output format (from old TODO)
+- Delete the old plain TODO file once this TODO.md lands
+- Add .aider.\* to .gitignore and remove the stray aider artifacts from the
+  working tree
+- Pick one tag scheme before the next release (v1.0.0 vs 1.0.1 are inconsistent)
+- Tag v1.0.2, with the leading v, once the attribute fix lands, so consuming
+  repos can move off pseudo-version pins in one step
+- Fix RELP output to cache (from old TODO)
+- Re-add RELP delivery over TCP to remote rsyslog imrelp; removed 2024-06-14
+  because it did not build (README planned feature)
+- Add regex filtering for webhook logs (from old TODO)
+- Better console output format (from old TODO)

package.json

@@ -0,0 +1,6 @@
+{
+  "private": true,
+  "devDependencies": {
+    "prettier": "3.8.1"
+  }
+}

script/bootstrap

@@ -2,11 +2,21 @@
 # script/bootstrap: install all dependencies needed to build and develop
 # this repo. Idempotent: every install is guarded by a check so already
 # installed tools are skipped. Base tooling comes from nix, apt, brew,
-# or apk (detected in that order); assumes nothing is present.
+# or apk (detected in that order); assumes nothing is present. Node is
+# used directly if installed; otherwise it is installed at a pinned
+# version via nvm (installing nvm itself first, from a hash-verified
+# release archive, never curl | sh).
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
+# Pinned versions, 2026-07-06
+NODE_VERSION="22.17.0"
+NVM_VERSION="0.40.3"
+# sha256 of https://github.com/nvm-sh/nvm/archive/refs/tags/v0.40.3.tar.gz
+NVM_SHA256="5f4d6aaa04a177dc93c985e31dbc411ab6b8c6e1e21d8015dbc1372625fcd1d0"
+YARN_VERSION="1.22.22"
+
 # goimports from golang.org/x/tools v0.30.0, 2025-02-10: the last release
 # that Go 1.22, the Go of go.mod and the Dockerfile, can build.
 GOIMPORTS_COMMIT="09747cdf594a7924dcecb506312be3bd6e437962"
@@ -81,6 +91,69 @@ ensure_goimports() {
     echo "goimports $GOIMPORTS_VERSION at $(command -v goimports)"
 }
 
+# verify_sha256 <file> <expected-hash>
+verify_sha256() {
+    if command -v sha256sum >/dev/null 2>&1; then
+        actual="$(sha256sum "$1" | cut -d' ' -f1)"
+    else
+        actual="$(shasum -a 256 "$1" | cut -d' ' -f1)"
+    fi
+    if [ "$actual" != "$2" ]; then
+        echo "bootstrap: sha256 mismatch for $1" >&2
+        echo "  expected: $2" >&2
+        echo "  actual:   $actual" >&2
+        exit 1
+    fi
+}
+
+# nvm is a bash script; run a command in a bash with nvm loaded
+nvm_sh() {
+    bash -c ". \"\$HOME/.nvm/nvm.sh\" && $*"
+}
+
+ensure_nvm() {
+    [ -s "$HOME/.nvm/nvm.sh" ] && return 0
+    # nvm prerequisites; nvm itself requires bash
+    if missing bash; then pkg_install bash bash bash bash; fi
+    if missing curl; then pkg_install curl curl curl curl; fi
+    if missing git; then pkg_install git git git git; fi
+    tmp="$(mktemp -d)"
+    curl -fsSL -o "$tmp/nvm.tar.gz" \
+        "https://github.com/nvm-sh/nvm/archive/refs/tags/v${NVM_VERSION}.tar.gz"
+    verify_sha256 "$tmp/nvm.tar.gz" "$NVM_SHA256"
+    mkdir -p "$HOME/.nvm"
+    tar -xzf "$tmp/nvm.tar.gz" -C "$HOME/.nvm" --strip-components=1
+    rm -rf "$tmp"
+}
+
+ensure_node() {
+    if ! missing node; then return 0; fi
+    ensure_nvm
+    nvm_sh "nvm install $NODE_VERSION"
+}
+
+ensure_yarn() {
+    if ! missing yarn; then return 0; fi
+    if ! missing corepack; then
+        corepack enable
+        corepack prepare "yarn@$YARN_VERSION" --activate
+    elif [ -s "$HOME/.nvm/nvm.sh" ]; then
+        nvm_sh "nvm use $NODE_VERSION >/dev/null && corepack enable && \
+            corepack prepare yarn@$YARN_VERSION --activate"
+    else
+        npm install -g "yarn@$YARN_VERSION"
+    fi
+}
+
+install_js_deps() {
+    if missing yarn && [ -s "$HOME/.nvm/nvm.sh" ]; then
+        nvm_sh "nvm use $NODE_VERSION >/dev/null && cd \"$ROOT\" && \
+            yarn install --frozen-lockfile"
+    else
+        yarn install --frozen-lockfile
+    fi
+}
+
 main() {
     cd "$ROOT"
 
@@ -93,6 +166,10 @@ main() {
 
     go mod download
 
+    ensure_node
+    ensure_yarn
+    install_js_deps
+
     echo "bootstrap complete"
 }
 

script/fmt

@@ -1,17 +1,37 @@
 #!/bin/sh
-# script/fmt: format all files (writes) with the goimports that
-# script/bootstrap installs. It puts Go's bin directory first on PATH, as
-# script/bootstrap does, so it runs that goimports even when the directory
-# is not on the caller's PATH.
+# script/fmt: format all files (writes): Go with the goimports that
+# script/bootstrap installs, then Markdown with prettier. It puts Go's bin
+# directory first on PATH, as script/bootstrap does, so it runs that
+# goimports even when the directory is not on the caller's PATH.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
+# Must match the pin in script/bootstrap.
+NODE_VERSION="22.17.0"
+
+# script/bootstrap installs node and yarn under nvm and leaves neither
+# on the PATH of the shell that called it, so resolve the pinned
+# toolchain here the way bootstrap's own install step does. nvm is a
+# bash script, hence the subshell.
+run_yarn() {
+    if command -v yarn >/dev/null 2>&1; then
+        exec yarn "$@"
+    fi
+    if [ ! -s "$HOME/.nvm/nvm.sh" ]; then
+        echo "fmt: no yarn; run script/bootstrap first" >&2
+        exit 1
+    fi
+    exec bash -c '. "$HOME/.nvm/nvm.sh" && nvm use "$1" >/dev/null &&
+        shift && exec yarn "$@"' bash "$NODE_VERSION" "$@"
+}
+
 main() {
     cd "$ROOT"
     gobin="$(go env GOBIN)"
     PATH="${gobin:-$(go env GOPATH)/bin}:$PATH"
     goimports -l -w .
+    run_yarn run prettier --write '**/*.md' --tab-width 4 --prose-wrap always
 }
 
 main "$@"

script/fmt-check

@@ -1,10 +1,30 @@
 #!/bin/sh
 # script/fmt-check: check formatting (read-only). Fails and lists the
-# offending files if gofmt would reformat anything.
+# offending files if gofmt would reformat any Go file; otherwise fails if
+# prettier would reformat any Markdown file.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
+# Must match the pin in script/bootstrap.
+NODE_VERSION="22.17.0"
+
+# script/bootstrap installs node and yarn under nvm and leaves neither
+# on the PATH of the shell that called it, so resolve the pinned
+# toolchain here the way bootstrap's own install step does. nvm is a
+# bash script, hence the subshell.
+run_yarn() {
+    if command -v yarn >/dev/null 2>&1; then
+        exec yarn "$@"
+    fi
+    if [ ! -s "$HOME/.nvm/nvm.sh" ]; then
+        echo "fmt-check: no yarn; run script/bootstrap first" >&2
+        exit 1
+    fi
+    exec bash -c '. "$HOME/.nvm/nvm.sh" && nvm use "$1" >/dev/null &&
+        shift && exec yarn "$@"' bash "$NODE_VERSION" "$@"
+}
+
 main() {
     cd "$ROOT"
     unformatted="$(gofmt -l .)"
@@ -13,6 +33,7 @@ main() {
         echo "$unformatted"
         exit 1
     fi
+    run_yarn run prettier --check '**/*.md' --tab-width 4 --prose-wrap always
 }
 
 main "$@"

yarn.lock

@@ -0,0 +1,8 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+prettier@3.8.1:
+  version "3.8.1"
+  resolved "https://registry.yarnpkg.com/prettier/-/prettier-3.8.1.tgz#edf48977cf991558f4fcbd8a3ba6015ba2a3a173"
+  integrity sha512-UOnG6LftzbdaHZcKoPFtOcCKztrQ57WkHDeRD9t/PTQtmT0NHSeWWepj6pS0z/N7+08BHFDQVUrfmfMRcZwbMg==