initial commit

internal/tokenengine/contract_test.go

@@ -0,0 +1,82 @@
+package tokenengine
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/urpi/go-bananas/internal/domain"
+)
+
+// The aggregate contract is consumed two ways: as a stylesheet the application
+// links, which can only be styled from :root, and as a stylesheet a control adopts
+// into its own shadow root, where :root matches nothing because a stylesheet in the
+// document does not select into a shadow tree. The bare selector forms are what make
+// the second use possible, and a palette preview depends on them, so their absence is
+// a silent failure: the selector still lists every palette and every preview renders
+// in whatever the host's fallbacks happen to be.
+
+// assertSelectorPair asserts that a selector list contains both halves of a pair as
+// distinct comma-separated entries.
+//
+// The assertion is on the joined pair rather than on each half alone, because one half
+// cannot tell the two forms apart: the string `[data-theme="acme"][data-mode="light"]`
+// occurs inside `:root[data-theme="acme"][data-mode="light"]`, so a bare Contains
+// reports a bare selector as present when only the rooted form was emitted. Joining
+// them is what discriminates, because in the rooted-only list the two halves are
+// separated by `:root`.
+func assertSelectorPair(t *testing.T, css, want string) {
+	t.Helper()
+	if !strings.Contains(css, want) {
+		t.Errorf("contract does not emit %q as a pair of entries, so a palette preview cannot adopt it", want)
+	}
+}
+
+func TestContractEmitsBareSelectorsForPreviewScope(t *testing.T) {
+	theme := testTheme()
+	theme.Slug = "acme"
+	theme.DefaultAppearance = domain.AppearanceDark
+	css := ContractAll([]*domain.Theme{theme})
+
+	// The palette on its own, so a preview that declares no appearance still adopts
+	// the designer's choice.
+	assertSelectorPair(t, css, `[data-theme="acme"], [data-bananas-theme="acme"]`)
+
+	// Each appearance, in both attribute conventions.
+	assertSelectorPair(t, css, `[data-theme="acme"][data-mode="light"], [data-bananas-theme="acme"][data-bananas-appearance="light"]`)
+	assertSelectorPair(t, css, `[data-theme="acme"][data-mode="dark"], [data-bananas-theme="acme"][data-bananas-appearance="dark"]`)
+
+	// The rooted forms have to survive: every application that links the contract
+	// rather than adopting it styles itself from :root.
+	assertSelectorPair(t, css, `:root[data-theme="acme"], :root[data-bananas-theme="acme"]`)
+	assertSelectorPair(t, css, `:root[data-theme="acme"][data-mode="light"], :root[data-bananas-theme="acme"][data-bananas-appearance="light"]`)
+}
+
+// TestContractBareSelectorsCarryTheSameValues guards against the two forms drifting
+// apart, which would mean a preview shows a different palette from the one applying
+// to the page. Both forms are emitted from the same declarations, so this is a
+// statement that the pairing is not an accident worth breaking.
+func TestContractBareSelectorsCarryTheSameValues(t *testing.T) {
+	css := ContractAll([]*domain.Theme{testTheme()})
+
+	for _, want := range []string{
+		`--bn-bg: #ffffff;`,
+		`--bn-text: #0f172a;`,
+		`--bn-accent: #4f46e5;`,
+	} {
+		if !strings.Contains(css, want) {
+			t.Errorf("contract no longer emits %q", want)
+		}
+	}
+}
+
+// TestContractLegacyAliasesStillExist protects the compatibility promise: an
+// application that already uses the unprefixed names must keep working.
+func TestContractLegacyAliasesStillExist(t *testing.T) {
+	css := ContractAll([]*domain.Theme{testTheme()})
+
+	for legacy := range legacyAliases {
+		if !strings.Contains(css, "--"+legacy+":") {
+			t.Errorf("legacy alias --%s is no longer emitted", legacy)
+		}
+	}
+}