Keep the AS list when the asupdate generator fails (closes #173)

make asupdate piped the generator into gzip, so the target saw gzip's
exit status. A failed download replaced pkg/asinfo/asdata.json.gz with
an empty file and the target still exited 0.

The target now runs the new script/asupdate. It writes the output of
cmd/asinfo-gen to a temporary file. Only when the generator succeeds
does it compress the list and move it into place. Otherwise it leaves
the file alone and exits non-zero. The generator now fails when as.csv
holds no AS.

The generator reads as.csv from ipverse/as-metadata, the source's new
name. The list it builds there is unchanged, so no new list is
committed.

Model: opus-5-5

Makefile

@@ -52,7 +52,6 @@ clean:
 run: build
 	DEBUG=routewatch ./bin/routewatch 2>&1 | tee log.txt
 
+# Rebuild the AS list built into RouteWatch from as.csv (needs the network).
 asupdate:
-	@echo "Updating AS info data..."
-	@go run cmd/asinfo-gen/main.go | gzip > pkg/asinfo/asdata.json.gz.tmp && \
-		mv pkg/asinfo/asdata.json.gz.tmp pkg/asinfo/asdata.json.gz
+	@script/asupdate

README.md

@@ -110,9 +110,10 @@ Every route answers `HEAD` as it answers `GET`, without the body.
       `handle` and `description`
 
     The search reads the AS list built into RouteWatch, not the database. The
-    list comes from [ipverse/asn-info](https://github.com/ipverse/asn-info). A
-    match can therefore be an AS that the database has no record of. A `q` that
-    is missing, empty or only spaces answers 400.
+    list comes from
+    [ipverse/as-metadata](https://github.com/ipverse/as-metadata). A match can
+    therefore be an AS that the database has no record of. A `q` that is
+    missing, empty or only spaces answers 400.
 
 A JSON answer is `{"status": "ok", "data": ...}`, or for an error
 `{"status": "error", "error": {"msg": ..., "code": ...}}`, and carries an
@@ -485,6 +486,11 @@ provide:
   or `go.sum`) and `go fmt` (writes), then `script/check`
 - `script/install-precommit` — install the git pre-commit hook that runs
   `script/precommit`
+- `script/asupdate` — rebuild the AS list built into RouteWatch,
+  `pkg/asinfo/asdata.json.gz`, from the `as.csv` file of
+  [ipverse/as-metadata](https://github.com/ipverse/as-metadata). It needs the
+  network. It runs `cmd/asinfo-gen`, which fails when it finds no AS. When
+  `cmd/asinfo-gen` fails, the old list stays and the script exits non-zero.
 
 Tests and the linter run only in Docker, as the `test` and `lint` phases of the
 `Dockerfile`; the image cannot be built unless both pass. Every `docker build`

TODO.md

@@ -33,6 +33,11 @@ tested.
 
 # Completed Steps
 
+- 2026-10-27: `make asupdate` runs the new `script/asupdate`. It replaces the AS
+  list built into RouteWatch only when the generator succeeds and finds at least
+  one AS. A failed download used to replace the list with an empty file. The
+  generator reads `as.csv` from `ipverse/as-metadata`, the source's new name
+  (closes #173)
 - 2026-10-27: the WHOIS details of an AS at RIPE, APNIC or AFRINIC come only
   from its `aut-num` object and the organisation object it names. RIPE and APNIC
   start their answer with the `as-block` object of the AS's block. Its dates

cmd/asinfo-gen/main.go

@@ -15,7 +15,7 @@ import (
 	"strings"
 )
 
-const asCsvURL = "https://github.com/ipverse/asn-info/raw/refs/heads/master/as.csv"
+const asCsvURL = "https://github.com/ipverse/as-metadata/raw/refs/heads/master/as.csv"
 
 // The first columns of as.csv, the ones the generator reads. It reads past
 // the columns after them, such as the country code.
@@ -26,7 +26,10 @@ const (
 	columnsRead       = 3
 )
 
-var errUnexpectedHeader = errors.New("unexpected CSV header")
+var (
+	errUnexpectedHeader = errors.New("unexpected CSV header")
+	errNoASes           = errors.New("no AS in the CSV")
+)
 
 // ASInfo represents information about an Autonomous System
 type ASInfo struct {
@@ -82,7 +85,7 @@ func main() {
 // parseCSV reads as.csv from r and returns its ASes, with the handle and the
 // description as the file spells them. A header whose first columns are not
 // the AS number, the handle and the description is an error. A record that
-// does not parse is logged and skipped.
+// does not parse is logged and skipped. A file left with no AS is an error.
 func parseCSV(r io.Reader) ([]ASInfo, error) {
 	reader := csv.NewReader(r)
 
@@ -126,5 +129,9 @@ func parseCSV(r io.Reader) ([]ASInfo, error) {
 		})
 	}
 
+	if len(asInfos) == 0 {
+		return nil, errNoASes
+	}
+
 	return asInfos, nil
 }

cmd/asinfo-gen/main_test.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"slices"
 	"strings"
 	"testing"
@@ -53,3 +54,20 @@ func TestParseCSVRejectsAnotherHeader(t *testing.T) {
 		}
 	}
 }
+
+// TestParseCSVRejectsAFileWithNoASes parses files that hold no AS, one with
+// only the header and one whose only record has no valid AS number. It
+// expects errNoASes, so that make asupdate keeps the old list.
+func TestParseCSVRejectsAFileWithNoASes(t *testing.T) {
+	t.Parallel()
+
+	for _, asCSV := range []string{
+		"asn,handle,description,country-code\n",
+		"asn,handle,description,country-code\nAS1,LVLT-1,Level 3,US\n",
+	} {
+		_, err := parseCSV(strings.NewReader(asCSV))
+		if !errors.Is(err, errNoASes) {
+			t.Errorf("parseCSV(%q) = %v, want %v", asCSV, err, errNoASes)
+		}
+	}
+}

pkg/asinfo/doc.go

@@ -2,7 +2,7 @@
 Package asinfo provides information about Autonomous Systems (AS).
 
 The package embeds a comprehensive database of AS numbers, handles, and descriptions
-sourced from https://github.com/ipverse/asn-info. The data is embedded at compile
+sourced from https://github.com/ipverse/as-metadata. The data is embedded at compile
 time and provides fast, offline lookups.
 
 Basic usage:

script/asupdate

@@ -0,0 +1,34 @@
+#!/bin/sh
+# script/asupdate: rebuild the AS list built into RouteWatch from
+# as.csv with cmd/asinfo-gen, which fails when it finds no AS. The new
+# list replaces the old one only when the generator succeeds. Otherwise
+# the old list stays as it was and the script exits non-zero.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+AS_DATA="pkg/asinfo/asdata.json.gz"
+# Next to AS_DATA, so the final mv is a rename on one file system.
+AS_DATA_TMP="$AS_DATA.tmp"
+
+main() {
+    cd "$ROOT"
+
+    json="$(mktemp)"
+    trap 'rm -f "$json" "$AS_DATA_TMP"' EXIT
+    # A signal exits through the EXIT trap too.
+    trap 'exit 1' HUP INT TERM
+
+    echo "Updating AS info data..."
+    if ! go run ./cmd/asinfo-gen >"$json"; then
+        echo "asupdate: the generator failed; $AS_DATA is unchanged" >&2
+        exit 1
+    fi
+
+    # -n leaves the time out of the file, so an unchanged list gives the
+    # same bytes.
+    gzip -n -c <"$json" >"$AS_DATA_TMP"
+    mv "$AS_DATA_TMP" "$AS_DATA"
+}
+
+main "$@"