feat: initial release

Assisted-by: GLM 5.3 Flash

internal/base/wrap_pin_test.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: MIT
+
+package base
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+// TestWrapErrCarriesTagOnce pins the WrapErr contract the ten wrap
+// points rely on: the message carries the tensor tag and the operation
+// once each, whatever the inner error already carries, and the chain
+// stays open for errors.Is. The wrap these properties answer to used to
+// be fmt.Errorf("op: %w", err) over an Errf-built cause, which printed
+// the tag twice.
+func TestWrapErrCarriesTagOnce(t *testing.T) {
+	if got := WrapErr("Anything", nil); got != nil {
+		t.Fatalf("WrapErr of nil = %v, want nil", got)
+	}
+
+	// A bare cause the library did not build: the tag and the operation
+	// are added, once each.
+	bare := errors.New("the caller's own failure")
+	got := WrapErr("Jacobian", bare)
+	if want := "tensor: Jacobian: the caller's own failure"; got.Error() != want {
+		t.Errorf("WrapErr of a bare cause = %q, want %q", got.Error(), want)
+	}
+	if !errors.Is(got, bare) {
+		t.Errorf("WrapErr of a bare cause does not unwrap to it")
+	}
+
+	// A cause the library already tagged: the tag is not doubled.
+	tagged := Errf("the shape holds more elements than fit in an index")
+	got = WrapErr("Tile", tagged)
+	if want := "tensor: Tile: the shape holds more elements than fit in an index"; got.Error() != want {
+		t.Errorf("WrapErr of a tagged cause = %q, want %q", got.Error(), want)
+	}
+	if !errors.Is(got, tagged) {
+		t.Errorf("WrapErr of a tagged cause does not unwrap to it")
+	}
+	if n := strings.Count(got.Error(), "tensor: "); n != 1 {
+		t.Errorf("WrapErr message carries the tag %d times, want exactly one", n)
+	}
+
+	// A nested WrapErr composes the same way: each layer names its own
+	// operation and the tag still appears once.
+	inner := WrapErr("Concat", tagged)
+	got = WrapErr("Repeat", inner)
+	if want := "tensor: Repeat: Concat: the shape holds more elements than fit in an index"; got.Error() != want {
+		t.Errorf("nested WrapErr = %q, want %q", got.Error(), want)
+	}
+	if !errors.Is(got, tagged) {
+		t.Errorf("nested WrapErr does not unwrap down to the cause")
+	}
+}