feat: add must helper for short form error checking

must.go

@@ -0,0 +1,114 @@
+// Copyright 2025 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package tc
+
+// Must calls f with no arguments and asserts that the error return is nil
+// and returns the remaining single return value.
+// Must is an alias of [Must0_1].
+func Must[T any, E error, F func() (T, E)](c LikeC, f F) T {
+	c.Helper()
+	return Must0_1(c, f)
+}
+
+// Must0 calls f with no arguments and asserts that the error return is nil
+// and returns the remaining single return value.
+// Must0 is an alias of [Must0_1].
+func Must0[T any, E error, F func() (T, E)](c LikeC, f F) T {
+	c.Helper()
+	return Must0_1(c, f)
+}
+
+// Must1 calls f with one argument and asserts that the error return is nil
+// and returns the remaining single return value.
+// Must1 is an alias of [Must1_1].
+func Must1[T any, E error, A any, F func(A) (T, E)](c LikeC, f F, a A) T {
+	c.Helper()
+	return Must1_1(c, f, a)
+}
+
+// Must2 calls f with two arguments and asserts that the error return is nil
+// and returns the remaining single return value.
+// Must2 is an alias of [Must2_1].
+func Must2[T any, E error, A any, B any, F func(A, B) (T, E)](c LikeC, f F, a A, b B) T {
+	c.Helper()
+	return Must2_1(c, f, a, b)
+}
+
+// Must0_0 calls f with no arguments and asserts that the error return is nil
+// and returns no values.
+func Must0_0[E error, F func() E](c LikeC, f F) {
+	c.Helper()
+	err := f()
+	c.Assert(err, ErrorIsNil)
+}
+
+// Must1_0 calls f with one argument and asserts that the error return is nil
+// and returns no values.
+func Must1_0[E error, A any, F func(A) E](c LikeC, f F, a A) {
+	c.Helper()
+	err := f(a)
+	c.Assert(err, ErrorIsNil)
+}
+
+// Must2_0 calls f with two arguments and asserts that the error return is nil
+// and returns no values.
+func Must2_0[E error, A any, B any, F func(A, B) E](c LikeC, f F, a A, b B) {
+	c.Helper()
+	err := f(a, b)
+	c.Assert(err, ErrorIsNil)
+}
+
+// Must0_1 calls f with no arguments and asserts that the error return is nil
+// and returns the remaining single return value.
+func Must0_1[T any, E error, F func() (T, E)](c LikeC, f F) T {
+	c.Helper()
+	r, err := f()
+	c.Assert(err, ErrorIsNil)
+	return r
+}
+
+// Must1_1 calls f with one argument and asserts that the error return is nil
+// and returns the remaining single return value.
+func Must1_1[T any, E error, A any, F func(A) (T, E)](c LikeC, f F, a A) T {
+	c.Helper()
+	r, err := f(a)
+	c.Assert(err, ErrorIsNil)
+	return r
+}
+
+// Must2_1 calls f with two arguments and asserts that the error return is nil
+// and returns the remaining single return value.
+func Must2_1[T any, E error, A any, B any, F func(A, B) (T, E)](c LikeC, f F, a A, b B) T {
+	c.Helper()
+	r, err := f(a, b)
+	c.Assert(err, ErrorIsNil)
+	return r
+}
+
+// Must0_2 calls f with no arguments and asserts that the error return is nil
+// and returns the remaining two return values.
+func Must0_2[T any, T2 any, E error, F func() (T, T2, E)](c LikeC, f F) (T, T2) {
+	c.Helper()
+	r1, r2, err := f()
+	c.Assert(err, ErrorIsNil)
+	return r1, r2
+}
+
+// Must1_2 calls f with one argument and asserts that the error return is nil
+// and returns the remaining two return values.
+func Must1_2[T any, T2 any, E error, A any, F func(A) (T, T2, E)](c LikeC, f F, a A) (T, T2) {
+	c.Helper()
+	r1, r2, err := f(a)
+	c.Assert(err, ErrorIsNil)
+	return r1, r2
+}
+
+// Must2_2 calls f with two arguments and asserts that the error return is nil
+// and returns the remaining two return values.
+func Must2_2[T any, T2 any, E error, A any, B any, F func(A, B) (T, T2, E)](c LikeC, f F, a A, b B) (T, T2) {
+	c.Helper()
+	r1, r2, err := f(a, b)
+	c.Assert(err, ErrorIsNil)
+	return r1, r2
+}