Fix TestCampaign sending only subscribers, failing listmonk validation

listmonk's /api/campaigns/:id/test handler binds the request into the
same campReq struct create/update use and validates it in full, so a
request with only {"subscribers": [...]} fails with "Invalid length
for name" before subscribers is ever read. TestCampaign now sends the
campaign's full CampaignInput alongside subscribers.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -68,6 +68,18 @@ plaintext alternative itself.
 - **`type`** — defaults to `regular`. `optin` isn't supported and is rejected at sync time.
 - **`scheduled_at` doesn't exist** — deliberately, since listmonk auto-sends a `scheduled` campaign the moment it fires, which would let a plain `git push` cause a real send.
 
+## Personalization
+
+Listmonk renders each recipient's campaign body as a Go template before converting Markdown to HTML, so a subscriber's `attribs` can be referenced directly in `campaign.md`'s body. `eec`'s signup forms set `first_name` (and `last_name`, if given) as attribs on every subscriber who provides one — subscribers who signed up before that (or via the public form when it collected email only) won't have it set.
+
+Verified working syntax, with a fallback for subscribers who don't have `first_name` set:
+
+```
+{{ if .Subscriber.Attribs.first_name }}Hi {{ .Subscriber.Attribs.first_name }},{{ else }}Hi there,{{ end }}
+```
+
+**Don't trust listmonk's `/api/campaigns/:id/preview` endpoint (or its admin-UI "Preview" button) to test this** — it always renders against listmonk's built-in demo subscriber (`demo@listmonk.app`, attribs `{city: Bengaluru}`), ignoring which subscriber you're looking at, so `first_name` will always look unset there even when it's really set on a real subscriber. Use `campaigns test SLUG EMAIL...` (a real test-send to a real subscriber's own address) to verify personalization actually renders — that's how the syntax above was confirmed.
+
 ## Segmentation
 
 `segment_query` is a raw Postgres-style SQL boolean expression — the same mechanism listmonk's own admin UI search box accepts. Since a campaign can only target whole list(s), `sync` materializes the query into a managed list:
@@ -107,8 +119,8 @@ A starting template (listmonk's own stock `default.tpl`, with the required `{{ U
 
 Each domain/client gets its own content repo, isolated by ordinary Gitea repo permissions — a client with push access to their repo has no path to any other domain's listmonk credentials, because those credentials simply don't exist in their repo.
 
-1. Create a new Gitea repo (e.g. `<client>-campaigns`), private.
-2. Add: an empty `campaigns/` directory, `email-templates/campaign.html` (copy the stock template from an existing content repo, or listmonk's own `static/email-templates/default.tpl`), and `.gitea/workflows/{sync,send,test,sync-template}.yml` copied from an existing content repo — each does `go install gitea.reground.org/will/eec-campaigns@<pinned-tag>` then runs the corresponding subcommand, with that repo's own secrets.
+1. Generate a new repo from [`campaigns-template`](https://gitea.reground.org/will/campaigns-template) (Gitea's "Generate Repo," not a clone/fork — it starts the new repo with its own clean history), private.
+2. Follow that generated repo's README checklist: rename the default-template name, restyle `email-templates/campaign.html` if needed, add secrets, confirm the tool version pin, run `Sync default campaign template` once, replace the README with a short domain-specific one.
 3. Add repo secrets: `CAMPAIGNS_LISTMONK_BASE_URL`, `CAMPAIGNS_LISTMONK_API_USER`, `CAMPAIGNS_LISTMONK_API_TOKEN`, and optionally `CAMPAIGNS_PREVIEW_EMAIL` — scoped to that domain's own listmonk instance and API user.
 4. Manually run the `Sync default campaign template` workflow once before the first real send.
 

internal/campaign/send.go

@@ -39,5 +39,5 @@ func Test(lm *listmonk.Client, slug string, emails []string) error {
 	if camp == nil {
 		return fmt.Errorf("no campaign named %q in listmonk — run sync first", slug)
 	}
-	return lm.TestCampaign(camp.ID, emails)
+	return lm.TestCampaign(camp.ID, camp.AsInput(), emails)
 }

internal/campaign/sync.go

@@ -137,7 +137,7 @@ func syncOne(lm *listmonk.Client, slug, dir, path string, defaultPreviewEmails [
 	}
 	var previewErr error
 	if len(recipients) > 0 {
-		previewErr = lm.TestCampaign(campaignID, recipients)
+		previewErr = lm.TestCampaign(campaignID, input, recipients)
 	}
 	return syncOneResult{Changed: true, PreviewErr: previewErr}, nil
 }

internal/listmonk/listmonk.go

@@ -297,6 +297,23 @@ type Campaign struct {
 	MediaIDs   []int
 }
 
+// AsInput converts a fetched Campaign back into the CampaignInput shape,
+// for callers (e.g. Test) that need to re-send a campaign's current fields
+// against an endpoint that validates the full campaign body.
+func (camp *Campaign) AsInput() CampaignInput {
+	return CampaignInput{
+		Name:       camp.Name,
+		Subject:    camp.Subject,
+		FromEmail:  camp.FromEmail,
+		TemplateID: camp.TemplateID,
+		Type:       camp.Type,
+		Tags:       camp.Tags,
+		ListIDs:    camp.ListIDs,
+		Body:       camp.Body,
+		MediaIDs:   camp.MediaIDs,
+	}
+}
+
 // CampaignInput is what sync.go builds from a campaign's frontmatter+body to
 // create or update a listmonk campaign.
 type CampaignInput struct {
@@ -482,14 +499,18 @@ func (c *Client) SetCampaignStatus(id int, status string) error {
 }
 
 // TestCampaign sends a preview of the campaign's current content to the
-// given addresses without touching its status. Request field confirmed
-// against knadh/listmonk's actual handler source (cmd/campaigns.go's
-// campReq.SubscriberEmails, json tag "subscribers").
-func (c *Client) TestCampaign(id int, emails []string) error {
+// given addresses without touching its status. listmonk's test-send handler
+// binds the request into the same campReq struct create/update use and
+// validates it in full, so the campaign's other fields (in particular a
+// non-empty "name") must be sent alongside "subscribers" — a request with
+// just {"subscribers": [...]} fails listmonk's own validation with "Invalid
+// length for name" before the "subscribers" field is ever looked at.
+func (c *Client) TestCampaign(id int, in CampaignInput, emails []string) error {
 	if len(emails) == 0 {
 		return nil
 	}
-	payload := map[string]any{"subscribers": emails}
+	payload := in.payload()
+	payload["subscribers"] = emails
 	respBody, status, err := c.do(http.MethodPost, fmt.Sprintf("/api/campaigns/%d/test", id), payload)
 	if err != nil {
 		return fmt.Errorf("sending test for campaign %d: %w", id, err)

internal/listmonk/listmonk_test.go

@@ -311,13 +311,17 @@ func TestTestCampaign_SendsSubscribersList(t *testing.T) {
 	defer srv.Close()
 
 	c := New(srv.URL, "u", "t")
-	if err := c.TestCampaign(7, []string{"me@example.com"}); err != nil {
+	in := CampaignInput{Name: "launch", Subject: "Hi", Body: "body", Type: "regular"}
+	if err := c.TestCampaign(7, in, []string{"me@example.com"}); err != nil {
 		t.Fatalf("TestCampaign: %v", err)
 	}
 	subs, ok := gotBody["subscribers"].([]any)
 	if !ok || len(subs) != 1 || subs[0] != "me@example.com" {
 		t.Errorf("expected subscribers=[me@example.com], got %+v", gotBody)
 	}
+	if gotBody["name"] != "launch" {
+		t.Errorf("expected the full campaign body (name=launch) alongside subscribers, got %+v", gotBody)
+	}
 }
 
 func TestErrorResponsesAreWrappedWithStatusAndBody(t *testing.T) {