Decode Datastar signals without the SDK

The SDK was used for exactly one call, ReadSignals, which is a JSON decode of
a query parameter. It brought four modules with it, including an HTTP
compression stack, for an SSE generator this app never touches: the search
handlers answer with plain text/html and let Datastar match the fragment by
id.

Five lines replace it. Absent or empty is deliberately not an error — the
first request carries no signals, and rejecting it would 400 the initial
load. Tests cover absent, empty, malformed, and extra signals present.

Nothing changes on the client: Datastar still sends the same
?datastar={"haku":"..."}, and the smoke checks that assert that wire format
are what make the swap safe.

cmd/foodster/handlers.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"database/sql"
+	"encoding/json"
 	"errors"
 	"io"
 	"log"
@@ -11,7 +12,6 @@ import (
 	"time"
 
 	"github.com/a-h/templ"
-	"github.com/starfederation/datastar-go/datastar"
 )
 
 // maxUpload caps a pasted or uploaded bundle. A household catalog is a few
@@ -167,6 +167,20 @@ type searchSignals struct {
 	Haku string `json:"haku"`
 }
 
+// readSignals decodes that parameter.
+//
+// ponytail: the Datastar SDK does this too, but pulling it in for one JSON
+// decode dragged along four modules — an HTTP compression stack among them —
+// for an SSE generator this app never uses. Absent or empty is not an error:
+// the first request carries no signals.
+func readSignals(r *http.Request, into any) error {
+	raw := r.URL.Query().Get("datastar")
+	if raw == "" {
+		return nil
+	}
+	return json.Unmarshal([]byte(raw), into)
+}
+
 // fragment renders a piece of a page for Datastar to patch in. A plain
 // text/html response is enough — Datastar matches the returned element by its
 // id and replaces it, so there is no SSE stream to manage.
@@ -180,7 +194,7 @@ func fragment(w http.ResponseWriter, r *http.Request, c templ.Component) {
 // searchBoard re-renders the dish board as the search box is typed into.
 func (a *app) searchBoard(w http.ResponseWriter, r *http.Request) {
 	var signals searchSignals
-	if err := datastar.ReadSignals(r, &signals); err != nil {
+	if err := readSignals(r, &signals); err != nil {
 		http.Error(w, "bad signals", http.StatusBadRequest)
 		return
 	}
@@ -204,7 +218,7 @@ func (a *app) searchBoard(w http.ResponseWriter, r *http.Request) {
 // searchCatalog re-renders the catalog lists as the search box is typed into.
 func (a *app) searchCatalog(w http.ResponseWriter, r *http.Request) {
 	var signals searchSignals
-	if err := datastar.ReadSignals(r, &signals); err != nil {
+	if err := readSignals(r, &signals); err != nil {
 		http.Error(w, "bad signals", http.StatusBadRequest)
 		return
 	}

cmd/foodster/main_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"net/http"
 	"net/http/httptest"
+	"net/url"
 	"os"
 	"strings"
 	"testing"
@@ -75,6 +76,35 @@ func TestDateRejectsTheFuture(t *testing.T) {
 	}
 }
 
+func TestReadSignals(t *testing.T) {
+	cases := []struct {
+		name    string
+		query   string
+		want    string
+		wantErr bool
+	}{
+		{"a signal", `/etsi?datastar=` + url.QueryEscape(`{"haku":"keitto"}`), "keitto", false},
+		{"other signals are ignored", `/etsi?datastar=` + url.QueryEscape(`{"haku":"kala","muu":1}`), "kala", false},
+		// The first request carries no signals at all; that is not a failure.
+		{"no parameter", "/etsi", "", false},
+		{"empty parameter", "/etsi?datastar=", "", false},
+		{"malformed json", "/etsi?datastar=%7Bnope", "", true},
+	}
+
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			var got searchSignals
+			err := readSignals(httptest.NewRequest(http.MethodGet, c.query, nil), &got)
+			if (err != nil) != c.wantErr {
+				t.Fatalf("err = %v, wantErr %v", err, c.wantErr)
+			}
+			if got.Haku != c.want {
+				t.Errorf("haku = %q, want %q", got.Haku, c.want)
+			}
+		})
+	}
+}
+
 func TestMigrateCreatesSchema(t *testing.T) {
 	db, err := openDB(t.TempDir() + "/test.db")
 	if err != nil {

go.mod

@@ -6,13 +6,11 @@ tool github.com/a-h/templ/cmd/templ
 
 require (
 	github.com/a-h/templ v0.3.1020
-	github.com/starfederation/datastar-go v1.2.2
 	golang.org/x/time v0.15.0
 	modernc.org/sqlite v1.58.0
 )
 
 require (
-	github.com/CAFxX/httpcompression v0.0.9 // indirect
 	github.com/a-h/parse v0.0.0-20250122154542-74294addb73e // indirect
 	github.com/andybalholm/brotli v1.2.0 // indirect
 	github.com/cenkalti/backoff/v4 v4.3.0 // indirect
@@ -21,13 +19,11 @@ require (
 	github.com/fatih/color v1.16.0 // indirect
 	github.com/fsnotify/fsnotify v1.7.0 // indirect
 	github.com/google/uuid v1.6.0 // indirect
-	github.com/klauspost/compress v1.18.0 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.24 // indirect
 	github.com/natefinch/atomic v1.0.1 // indirect
 	github.com/ncruces/go-strftime v1.0.0 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
-	github.com/valyala/bytebufferpool v1.0.0 // indirect
 	golang.org/x/mod v0.38.0 // indirect
 	golang.org/x/net v0.57.0 // indirect
 	golang.org/x/sync v0.22.0 // indirect

go.sum

@@ -1,17 +1,13 @@
-github.com/CAFxX/httpcompression v0.0.9 h1:0ue2X8dOLEpxTm8tt+OdHcgA+gbDge0OqFQWGKSqgrg=
-github.com/CAFxX/httpcompression v0.0.9/go.mod h1:XX8oPZA+4IDcfZ0A71Hz0mZsv/YJOgYygkFhizVPilM=
 github.com/a-h/parse v0.0.0-20250122154542-74294addb73e h1:HjVbSQHy+dnlS6C3XajZ69NYAb5jbGNfHanvm1+iYlo=
 github.com/a-h/parse v0.0.0-20250122154542-74294addb73e/go.mod h1:3mnrkvGpurZ4ZrTDbYU84xhwXW2TjTKShSwjRi2ihfQ=
 github.com/a-h/templ v0.3.1020 h1:ypAT/L5ySWEnZ6Zft/5yfoWXYYkhFNvEFOeeqecg4tw=
 github.com/a-h/templ v0.3.1020/go.mod h1:A2DlK61v+K+NRoGnhmYbNYVmtYHcFO5/AisMvBdDxTM=
-github.com/andybalholm/brotli v1.0.5/go.mod h1:fO7iG3H7G2nSZ7m0zPUDn85XEX2GTukHGRSepvi9Eig=
 github.com/andybalholm/brotli v1.2.0 h1:ukwgCxwYrmACq68yiUqwIWnGY0cTPox/M94sVwToPjQ=
 github.com/andybalholm/brotli v1.2.0/go.mod h1:rzTDkvFWvIrjDXZHkuS16NPggd91W3kUSvPlQ1pLaKY=
 github.com/cenkalti/backoff/v4 v4.3.0 h1:MyRJ/UdXutAwSAT+s3wNd7MfTIcy71VQueUuFK343L8=
 github.com/cenkalti/backoff/v4 v4.3.0/go.mod h1:Y3VNntkOUPxTVeUxJ/G5vcM//AlwfmyYozVcomhLiZE=
 github.com/cli/browser v1.3.0 h1:LejqCrpWr+1pRqmEPDGnTZOjsMe7sehifLynZJuqJpo=
 github.com/cli/browser v1.3.0/go.mod h1:HH8s+fOAxjhQoBUAsKuPCbqUuxZDhQ2/aD+SzsEfBTk=
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dustin/go-humanize v1.0.1 h1:GzkhY7T5VNhEkwH0PVJgjz+fX1rhBrR7pRT3mDkpeCY=
@@ -20,8 +16,6 @@ github.com/fatih/color v1.16.0 h1:zmkK9Ngbjj+K0yRhTVONQh1p/HknKYSlNT+vZCzyokM=
 github.com/fatih/color v1.16.0/go.mod h1:fL2Sau1YI5c0pdGEVCbKQbLXB6edEj1ZgiY4NijnWvE=
 github.com/fsnotify/fsnotify v1.7.0 h1:8JEhPFa5W2WU7YfeZzPNqzMP6Lwt7L2715Ggo0nosvA=
 github.com/fsnotify/fsnotify v1.7.0/go.mod h1:40Bi/Hjc2AVfZrqy+aj+yEI+/bRxZnMJyTJwOpGvigM=
-github.com/google/brotli/go/cbrotli v0.0.0-20230829110029-ed738e842d2f h1:jopqB+UTSdJGEJT8tEqYyE29zN91fi2827oLET8tl7k=
-github.com/google/brotli/go/cbrotli v0.0.0-20230829110029-ed738e842d2f/go.mod h1:nOPhAkwVliJdNTkj3gXpljmWhjc4wCaVqbMJcPKWP4s=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/pprof v0.0.0-20260802141513-ef3492d7dac3 h1:LMLX+LgTNWpfvCBdFebv6EsYotImrt/Ppc5cXIriCSo=
@@ -30,10 +24,6 @@ github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/hashicorp/golang-lru/v2 v2.0.7 h1:a+bsQ5rvGLjzHuww6tVxozPZFVghXaHOwFs4luLUK2k=
 github.com/hashicorp/golang-lru/v2 v2.0.7/go.mod h1:QeFd9opnmA6QUJc5vARoKUSoFhyfM2/ZepoAG6RGpeM=
-github.com/klauspost/compress v1.16.7/go.mod h1:ntbaceVETuRiXiv4DpjP66DpAtAGkEQskQzEyD//IeE=
-github.com/klauspost/compress v1.18.0 h1:c/Cqfb0r+Yi+JtIEq73FWXVkRonBlf0CRNYc8Zttxdo=
-github.com/klauspost/compress v1.18.0/go.mod h1:2Pp+KzxcywXVXMr50+X0Q/Lsb43OQHYWRCY2AiWywWQ=
-github.com/klauspost/pgzip v1.2.6/go.mod h1:Ch1tH69qFZu15pkjo5kYi6mth2Zzwzt50oCQKQE9RUs=
 github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
 github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovkB8vQcUbaXHg=
 github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
@@ -43,27 +33,12 @@ github.com/natefinch/atomic v1.0.1 h1:ZPYKxkqQOx3KZ+RsbnP/YsgvxWQPGxjC0oBt2AhwV0
 github.com/natefinch/atomic v1.0.1/go.mod h1:N/D/ELrljoqDyT3rZrsUmtsuzvHkeB/wWjHV22AZRbM=
 github.com/ncruces/go-strftime v1.0.0 h1:HMFp8mLCTPp341M/ZnA4qaf7ZlsbTc+miZjCLOFAw7w=
 github.com/ncruces/go-strftime v1.0.0/go.mod h1:Fwc5htZGVVkseilnfgOVb9mKy6w1naJmn9CehxcKcls=
-github.com/pierrec/lz4/v4 v4.1.18 h1:xaKrnTkyoqfh1YItXl56+6KJNVYWlEEPuAQW9xsplYQ=
-github.com/pierrec/lz4/v4 v4.1.18/go.mod h1:gZWDp/Ze/IJXGXf23ltt2EXimqmTUXEy0GFuRQyBid4=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec h1:W09IVJc94icq4NjY3clb7Lk8O1qJ8BdBEF8z0ibU0rE=
 github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec/go.mod h1:qqbHyh8v60DhA7CoWK5oRCqLrMHRGoxYCSS9EjAz6Eo=
-github.com/starfederation/datastar-go v1.2.2 h1:f+U2y5FY5tXgXaTVXkuKu+Tz9uh7BU1j8jxthYmcC9Q=
-github.com/starfederation/datastar-go v1.2.2/go.mod h1:stm83LQkhZkwa5GzzdPEN6dLuu8FVwxIv0w1DYkbD3w=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
-github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
-github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
-github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
 github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
-github.com/ulikunitz/xz v0.5.11/go.mod h1:nbz6k7qbPmH4IRqmfOplQw/tblSgqTqBwxkY0oWt/14=
-github.com/valyala/bytebufferpool v1.0.0 h1:GqA5TC/0021Y/b9FG4Oi9Mr3q7XYx6KllzawFIhcdPw=
-github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=
-github.com/valyala/gozstd v1.20.1 h1:xPnnnvjmaDDitMFfDxmQ4vpx0+3CdTg2o3lALvXTU/g=
-github.com/valyala/gozstd v1.20.1/go.mod h1:y5Ew47GLlP37EkTB+B4s7r6A5rdaeB7ftbl9zoYiIPQ=
 github.com/xyproto/randomstring v1.0.5 h1:YtlWPoRdgMu3NZtP45drfy1GKoojuR7hmRcnhZqKjWU=
 github.com/xyproto/randomstring v1.0.5/go.mod h1:rgmS5DeNXLivK7YprL0pY+lTuhNQW3iGxZ18UQApw/E=
 golang.org/x/mod v0.38.0 h1:MECBjubtXD7yj4HrhIUcywNaGeNVUdfVnxmPajOk4yk=
@@ -79,8 +54,6 @@ golang.org/x/time v0.15.0 h1:bbrp8t3bGUeFOx08pvsMYRTCVSMk89u4tKbNOZbp88U=
 golang.org/x/time v0.15.0/go.mod h1:Y4YMaQmXwGQZoFaVFk4YpCt4FLQMYKZe9oeV/f4MSno=
 golang.org/x/tools v0.48.0 h1:3+hClM1aLL5mjMKm5ovokw9epgRXPuu2tILgismM6RE=
 golang.org/x/tools v0.48.0/go.mod h1:08xX0orndb/F7jJxGDicx061tyd5pcMto75YMAXr6lk=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 modernc.org/cc/v4 v4.29.2 h1:h6+9ciCnPKutf4I03CvheAvDLX7+IHlqR6Iy6J+cgd8=