chore(api)!: Error instead of returning 0 on invalid inputs to conv.* functions (#2104)

Signed-off-by: Dave Henderson <dhenderson@gmail.com>

11 files changed, 630 insertions, 160 deletions

diff --git a/internal/funcs/coll.go b/internal/funcs/coll.go
index 9e08aeac..945f77d3 100644
--- a/internal/funcs/coll.go
+++ b/internal/funcs/coll.go
@@ -153,12 +153,20 @@ func (CollFuncs) Flatten(args ...interface{}) ([]interface{}, error) {
 	if len(args) == 0 || len(args) > 2 {
 		return nil, fmt.Errorf("wrong number of args: wanted 1 or 2, got %d", len(args))
 	}
+
 	list := args[0]
+
+	var err error
 	depth := -1
 	if len(args) == 2 {
-		depth = conv.ToInt(args[0])
+		depth, err = conv.ToInt(list)
+		if err != nil {
+			return nil, fmt.Errorf("wrong depth type: must be int, got %T (%+v)", list, list)
+		}
+
 		list = args[1]
 	}
+
 	return coll.Flatten(list, depth)
 }
 
diff --git a/internal/funcs/conv.go b/internal/funcs/conv.go
index 5bc5cab9..67fd3b9f 100644
--- a/internal/funcs/conv.go
+++ b/internal/funcs/conv.go
@@ -3,6 +3,7 @@ package funcs
 import (
 	"context"
 	"net/url"
+	"strconv"
 	"text/template"
 
 	"github.com/hairyhenderson/gomplate/v4/conv"
@@ -52,23 +53,23 @@ func (ConvFuncs) Join(in interface{}, sep string) (string, error) {
 }
 
 // ParseInt -
-func (ConvFuncs) ParseInt(s interface{}, base, bitSize int) int64 {
-	return conv.MustParseInt(conv.ToString(s), base, bitSize)
+func (ConvFuncs) ParseInt(s interface{}, base, bitSize int) (int64, error) {
+	return strconv.ParseInt(conv.ToString(s), base, bitSize)
 }
 
 // ParseFloat -
-func (ConvFuncs) ParseFloat(s interface{}, bitSize int) float64 {
-	return conv.MustParseFloat(conv.ToString(s), bitSize)
+func (ConvFuncs) ParseFloat(s interface{}, bitSize int) (float64, error) {
+	return strconv.ParseFloat(conv.ToString(s), bitSize)
 }
 
 // ParseUint -
-func (ConvFuncs) ParseUint(s interface{}, base, bitSize int) uint64 {
-	return conv.MustParseUint(conv.ToString(s), base, bitSize)
+func (ConvFuncs) ParseUint(s interface{}, base, bitSize int) (uint64, error) {
+	return strconv.ParseUint(conv.ToString(s), base, bitSize)
 }
 
 // Atoi -
-func (ConvFuncs) Atoi(s interface{}) int {
-	return conv.MustAtoi(conv.ToString(s))
+func (ConvFuncs) Atoi(s interface{}) (int, error) {
+	return strconv.Atoi(conv.ToString(s))
 }
 
 // URL -
@@ -77,32 +78,32 @@ func (ConvFuncs) URL(s interface{}) (*url.URL, error) {
 }
 
 // ToInt64 -
-func (ConvFuncs) ToInt64(in interface{}) int64 {
+func (ConvFuncs) ToInt64(in interface{}) (int64, error) {
 	return conv.ToInt64(in)
 }
 
 // ToInt -
-func (ConvFuncs) ToInt(in interface{}) int {
+func (ConvFuncs) ToInt(in interface{}) (int, error) {
 	return conv.ToInt(in)
 }
 
 // ToInt64s -
-func (ConvFuncs) ToInt64s(in ...interface{}) []int64 {
+func (ConvFuncs) ToInt64s(in ...interface{}) ([]int64, error) {
 	return conv.ToInt64s(in...)
 }
 
 // ToInts -
-func (ConvFuncs) ToInts(in ...interface{}) []int {
+func (ConvFuncs) ToInts(in ...interface{}) ([]int, error) {
 	return conv.ToInts(in...)
 }
 
 // ToFloat64 -
-func (ConvFuncs) ToFloat64(in interface{}) float64 {
+func (ConvFuncs) ToFloat64(in interface{}) (float64, error) {
 	return conv.ToFloat64(in)
 }
 
 // ToFloat64s -
-func (ConvFuncs) ToFloat64s(in ...interface{}) []float64 {
+func (ConvFuncs) ToFloat64s(in ...interface{}) ([]float64, error) {
 	return conv.ToFloat64s(in...)
 }
 
@@ -121,5 +122,6 @@ func (ConvFuncs) Default(def, in interface{}) interface{} {
 	if truth, ok := template.IsTrue(in); truth && ok {
 		return in
 	}
+
 	return def
 }
diff --git a/internal/funcs/crypto.go b/internal/funcs/crypto.go
index fab02a7a..8807d518 100644
--- a/internal/funcs/crypto.go
+++ b/internal/funcs/crypto.go
@@ -49,8 +49,16 @@ func (CryptoFuncs) PBKDF2(password, salt, iter, keylen interface{}, hashFunc ...
 	}
 	pw := toBytes(password)
 	s := toBytes(salt)
-	i := conv.ToInt(iter)
-	kl := conv.ToInt(keylen)
+
+	i, err := conv.ToInt(iter)
+	if err != nil {
+		return "", fmt.Errorf("iter must be an integer: %w", err)
+	}
+
+	kl, err := conv.ToInt(keylen)
+	if err != nil {
+		return "", fmt.Errorf("keylen must be an integer: %w", err)
+	}
 
 	dk, err := crypto.PBKDF2(pw, s, i, kl, h)
 	return fmt.Sprintf("%02x", dk), err
@@ -167,17 +175,24 @@ func (CryptoFuncs) SHA512_256Bytes(input interface{}) ([]byte, error) {
 // Bcrypt -
 func (CryptoFuncs) Bcrypt(args ...interface{}) (string, error) {
 	input := ""
+
+	var err error
 	cost := bcrypt.DefaultCost
-	if len(args) == 0 {
-		return "", fmt.Errorf("bcrypt requires at least an 'input' value")
-	}
-	if len(args) == 1 {
+
+	switch len(args) {
+	case 1:
 		input = conv.ToString(args[0])
-	}
-	if len(args) == 2 {
-		cost = conv.ToInt(args[0])
+	case 2:
+		cost, err = conv.ToInt(args[0])
+		if err != nil {
+			return "", fmt.Errorf("bcrypt cost must be an integer: %w", err)
+		}
+
 		input = conv.ToString(args[1])
+	default:
+		return "", fmt.Errorf("wrong number of args: want 1 or 2, got %d", len(args))
 	}
+
 	hash, err := bcrypt.GenerateFromPassword([]byte(input), cost)
 	return string(hash), err
 }
@@ -215,15 +230,21 @@ func (f *CryptoFuncs) RSADecryptBytes(key string, in []byte) ([]byte, error) {
 // RSAGenerateKey -
 // Experimental!
 func (f *CryptoFuncs) RSAGenerateKey(args ...interface{}) (string, error) {
-	if err := checkExperimental(f.ctx); err != nil {
+	err := checkExperimental(f.ctx)
+	if err != nil {
 		return "", err
 	}
+
 	bits := 4096
 	if len(args) == 1 {
-		bits = conv.ToInt(args[0])
+		bits, err = conv.ToInt(args[0])
+		if err != nil {
+			return "", fmt.Errorf("bits must be an integer: %w", err)
+		}
 	} else if len(args) > 1 {
 		return "", fmt.Errorf("wrong number of args: want 0 or 1, got %d", len(args))
 	}
+
 	out, err := crypto.RSAGenerateKey(bits)
 	return string(out), err
 }
@@ -370,7 +391,11 @@ func parseAESArgs(key string, args ...interface{}) ([]byte, []byte, error) {
 	case 1:
 		msg = toBytes(args[0])
 	case 2:
-		keyBits = conv.ToInt(args[0])
+		var err error
+		keyBits, err = conv.ToInt(args[0])
+		if err != nil {
+			return nil, nil, fmt.Errorf("keyBits must be an integer: %w", err)
+		}
 		msg = toBytes(args[1])
 	default:
 		return nil, nil, fmt.Errorf("wrong number of args: want 2 or 3, got %d", len(args))
diff --git a/internal/funcs/math.go b/internal/funcs/math.go
index 3881e057..694586a7 100644
--- a/internal/funcs/math.go
+++ b/internal/funcs/math.go
@@ -79,79 +79,158 @@ func (f MathFuncs) IsNum(n interface{}) bool {
 }
 
 // Abs -
-func (f MathFuncs) Abs(n interface{}) interface{} {
-	m := gmath.Abs(conv.ToFloat64(n))
+func (f MathFuncs) Abs(n interface{}) (interface{}, error) {
+	fn, err := conv.ToFloat64(n)
+	if err != nil {
+		return nil, fmt.Errorf("expected a number: %w", err)
+	}
+
+	m := gmath.Abs(fn)
 	if f.IsInt(n) {
 		return conv.ToInt64(m)
 	}
-	return m
+
+	return m, nil
 }
 
 // Add -
-func (f MathFuncs) Add(n ...interface{}) interface{} {
+func (f MathFuncs) Add(n ...interface{}) (interface{}, error) {
 	if f.containsFloat(n...) {
-		nums := conv.ToFloat64s(n...)
+		nums, err := conv.ToFloat64s(n...)
+		if err != nil {
+			return nil, fmt.Errorf("expected number inputs: %w", err)
+		}
+
 		var x float64
 		for _, v := range nums {
 			x += v
 		}
-		return x
+
+		return x, nil
+	}
+
+	nums, err := conv.ToInt64s(n...)
+	if err != nil {
+		return nil, fmt.Errorf("expected number inputs: %w", err)
 	}
-	nums := conv.ToInt64s(n...)
+
 	var x int64
 	for _, v := range nums {
 		x += v
 	}
-	return x
+
+	return x, nil
 }
 
 // Mul -
-func (f MathFuncs) Mul(n ...interface{}) interface{} {
+func (f MathFuncs) Mul(n ...interface{}) (interface{}, error) {
 	if f.containsFloat(n...) {
-		nums := conv.ToFloat64s(n...)
+		nums, err := conv.ToFloat64s(n...)
+		if err != nil {
+			return nil, fmt.Errorf("expected number inputs: %w", err)
+		}
+
 		x := 1.
 		for _, v := range nums {
 			x *= v
 		}
-		return x
+
+		return x, nil
+	}
+
+	nums, err := conv.ToInt64s(n...)
+	if err != nil {
+		return nil, fmt.Errorf("expected number inputs: %w", err)
 	}
-	nums := conv.ToInt64s(n...)
+
 	x := int64(1)
 	for _, v := range nums {
 		x *= v
 	}
-	return x
+
+	return x, nil
 }
 
 // Sub -
-func (f MathFuncs) Sub(a, b interface{}) interface{} {
+func (f MathFuncs) Sub(a, b interface{}) (interface{}, error) {
 	if f.containsFloat(a, b) {
-		return conv.ToFloat64(a) - conv.ToFloat64(b)
+		fa, err := conv.ToFloat64(a)
+		if err != nil {
+			return nil, fmt.Errorf("expected a number: %w", err)
+		}
+
+		fb, err := conv.ToFloat64(b)
+		if err != nil {
+			return nil, fmt.Errorf("expected a number: %w", err)
+		}
+
+		return fa - fb, nil
+	}
+
+	ia, err := conv.ToInt64(a)
+	if err != nil {
+		return nil, fmt.Errorf("expected a number: %w", err)
+	}
+
+	ib, err := conv.ToInt64(b)
+	if err != nil {
+		return nil, fmt.Errorf("expected a number: %w", err)
 	}
-	return conv.ToInt64(a) - conv.ToInt64(b)
+
+	return ia - ib, nil
 }
 
 // Div -
 func (f MathFuncs) Div(a, b interface{}) (interface{}, error) {
-	divisor := conv.ToFloat64(a)
-	dividend := conv.ToFloat64(b)
+	divisor, err := conv.ToFloat64(a)
+	if err != nil {
+		return nil, fmt.Errorf("expected a number: %w", err)
+	}
+
+	dividend, err := conv.ToFloat64(b)
+	if err != nil {
+		return nil, fmt.Errorf("expected a number: %w", err)
+	}
+
 	if dividend == 0 {
 		return 0, fmt.Errorf("error: division by 0")
 	}
+
 	return divisor / dividend, nil
 }
 
 // Rem -
-func (f MathFuncs) Rem(a, b interface{}) interface{} {
-	return conv.ToInt64(a) % conv.ToInt64(b)
+func (f MathFuncs) Rem(a, b interface{}) (interface{}, error) {
+	ia, err := conv.ToInt64(a)
+	if err != nil {
+		return nil, fmt.Errorf("expected a number: %w", err)
+	}
+
+	ib, err := conv.ToInt64(b)
+	if err != nil {
+		return nil, fmt.Errorf("expected a number: %w", err)
+	}
+
+	return ia % ib, nil
 }
 
 // Pow -
-func (f MathFuncs) Pow(a, b interface{}) interface{} {
-	r := gmath.Pow(conv.ToFloat64(a), conv.ToFloat64(b))
+func (f MathFuncs) Pow(a, b interface{}) (interface{}, error) {
+	fa, err := conv.ToFloat64(a)
+	if err != nil {
+		return nil, fmt.Errorf("expected a number: %w", err)
+	}
+
+	fb, err := conv.ToFloat64(b)
+	if err != nil {
+		return nil, fmt.Errorf("expected a number: %w", err)
+	}
+
+	r := gmath.Pow(fa, fb)
 	if f.IsFloat(a) {
-		return r
+		return r, nil
 	}
+
 	return conv.ToInt64(r)
 }
 
@@ -161,53 +240,116 @@ func (f MathFuncs) Seq(n ...interface{}) ([]int64, error) {
 	start := int64(1)
 	end := int64(0)
 	step := int64(1)
-	if len(n) == 0 {
-		return nil, fmt.Errorf("math.Seq must be given at least an 'end' value")
-	}
-	if len(n) == 1 {
-		end = conv.ToInt64(n[0])
-	}
-	if len(n) == 2 {
-		start = conv.ToInt64(n[0])
-		end = conv.ToInt64(n[1])
-	}
-	if len(n) == 3 {
-		start = conv.ToInt64(n[0])
-		end = conv.ToInt64(n[1])
-		step = conv.ToInt64(n[2])
+
+	var err error
+
+	switch len(n) {
+	case 1:
+		end, err = conv.ToInt64(n[0])
+		if err != nil {
+			return nil, fmt.Errorf("expected a number: %w", err)
+		}
+	case 2:
+		start, err = conv.ToInt64(n[0])
+		if err != nil {
+			return nil, fmt.Errorf("expected a number: %w", err)
+		}
+
+		end, err = conv.ToInt64(n[1])
+		if err != nil {
+			return nil, fmt.Errorf("expected a number: %w", err)
+		}
+	case 3:
+		start, err = conv.ToInt64(n[0])
+		if err != nil {
+			return nil, fmt.Errorf("expected a number: %w", err)
+		}
+
+		end, err = conv.ToInt64(n[1])
+		if err != nil {
+			return nil, fmt.Errorf("expected a number: %w", err)
+		}
+
+		step, err = conv.ToInt64(n[2])
+		if err != nil {
+			return nil, fmt.Errorf("expected a number: %w", err)
+		}
+	default:
+		return nil, fmt.Errorf("expected 1, 2, or 3 arguments, got %d", len(n))
 	}
-	return math.Seq(conv.ToInt64(start), conv.ToInt64(end), conv.ToInt64(step)), nil
+
+	return math.Seq(start, end, step), nil
 }
 
 // Max -
 func (f MathFuncs) Max(a interface{}, b ...interface{}) (interface{}, error) {
 	if f.IsFloat(a) || f.containsFloat(b...) {
-		m := conv.ToFloat64(a)
-		for _, n := range conv.ToFloat64s(b...) {
+		m, err := conv.ToFloat64(a)
+		if err != nil {
+			return nil, fmt.Errorf("expected a number: %w", err)
+		}
+
+		floats, err := conv.ToFloat64s(b...)
+		if err != nil {
+			return nil, fmt.Errorf("expected a number: %w", err)
+		}
+
+		for _, n := range floats {
 			m = gmath.Max(m, n)
 		}
+
 		return m, nil
 	}
-	m := conv.ToInt64(a)
-	for _, n := range conv.ToInt64s(b...) {
+
+	m, err := conv.ToInt64(a)
+	if err != nil {
+		return nil, fmt.Errorf("expected a number: %w", err)
+	}
+
+	nums, err := conv.ToInt64s(b...)
+	if err != nil {
+		return nil, fmt.Errorf("expected a number: %w", err)
+	}
+
+	for _, n := range nums {
 		if n > m {
 			m = n
 		}
 	}
+
 	return m, nil
 }
 
 // Min -
 func (f MathFuncs) Min(a interface{}, b ...interface{}) (interface{}, error) {
 	if f.IsFloat(a) || f.containsFloat(b...) {
-		m := conv.ToFloat64(a)
-		for _, n := range conv.ToFloat64s(b...) {
+		m, err := conv.ToFloat64(a)
+		if err != nil {
+			return nil, fmt.Errorf("expected a number: %w", err)
+		}
+
+		floats, err := conv.ToFloat64s(b...)
+		if err != nil {
+			return nil, fmt.Errorf("expected a number: %w", err)
+		}
+
+		for _, n := range floats {
 			m = gmath.Min(m, n)
 		}
 		return m, nil
 	}
-	m := conv.ToInt64(a)
-	for _, n := range conv.ToInt64s(b...) {
+
+	m, err := conv.ToInt64(a)
+	if err != nil {
+		return nil, fmt.Errorf("expected a number: %w", err)
+	}
+
+	nums, err := conv.ToInt64s(b...)
+	if err != nil {
+		return nil, fmt.Errorf("expected a number: %w", err)
+	}
+
+	for _, n := range nums {
 		if n < m {
 			m = n
 		}
@@ -216,16 +358,31 @@ func (f MathFuncs) Min(a interface{}, b ...interface{}) (interface{}, error) {
 }
 
 // Ceil -
-func (f MathFuncs) Ceil(n interface{}) interface{} {
-	return gmath.Ceil(conv.ToFloat64(n))
+func (f MathFuncs) Ceil(n interface{}) (interface{}, error) {
+	in, err := conv.ToFloat64(n)
+	if err != nil {
+		return nil, fmt.Errorf("n must be a number: %w", err)
+	}
+
+	return gmath.Ceil(in), nil
 }
 
 // Floor -
-func (f MathFuncs) Floor(n interface{}) interface{} {
-	return gmath.Floor(conv.ToFloat64(n))
+func (f MathFuncs) Floor(n interface{}) (interface{}, error) {
+	in, err := conv.ToFloat64(n)
+	if err != nil {
+		return nil, fmt.Errorf("n must be a number: %w", err)
+	}
+
+	return gmath.Floor(in), nil
 }
 
 // Round -
-func (f MathFuncs) Round(n interface{}) interface{} {
-	return gmath.Round(conv.ToFloat64(n))
+func (f MathFuncs) Round(n interface{}) (interface{}, error) {
+	in, err := conv.ToFloat64(n)
+	if err != nil {
+		return nil, fmt.Errorf("n must be a number: %w", err)
+	}
+
+	return gmath.Round(in), nil
 }
diff --git a/internal/funcs/math_test.go b/internal/funcs/math_test.go
index 50b05784..8df794fc 100644
--- a/internal/funcs/math_test.go
+++ b/internal/funcs/math_test.go
@@ -32,33 +32,78 @@ func TestAdd(t *testing.T) {
 	t.Parallel()
 
 	m := MathFuncs{}
-	assert.Equal(t, int64(12), m.Add(1, 1, 2, 3, 5))
-	assert.Equal(t, int64(2), m.Add(1, 1))
-	assert.Equal(t, int64(1), m.Add(1))
-	assert.Equal(t, int64(0), m.Add(-5, 5))
-	assert.InEpsilon(t, float64(5.1), m.Add(4.9, "0.2"), 1e-12)
+
+	actual, err := m.Add(1, 1, 2, 3, 5)
+	require.NoError(t, err)
+	assert.Equal(t, int64(12), actual)
+
+	actual, err = m.Add(1, 1)
+	require.NoError(t, err)
+	assert.Equal(t, int64(2), actual)
+
+	actual, err = m.Add(1)
+	require.NoError(t, err)
+	assert.Equal(t, int64(1), actual)
+
+	actual, err = m.Add(-5, 5)
+	require.NoError(t, err)
+	assert.Equal(t, int64(0), actual)
+
+	actual, err = m.Add(4.9, "0.2")
+	require.NoError(t, err)
+	assert.InEpsilon(t, float64(5.1), actual, 1e-12)
 }
 
 func TestMul(t *testing.T) {
 	t.Parallel()
 
 	m := MathFuncs{}
-	assert.Equal(t, int64(30), m.Mul(1, 1, 2, 3, 5))
-	assert.Equal(t, int64(1), m.Mul(1, 1))
-	assert.Equal(t, int64(1), m.Mul(1))
-	assert.Equal(t, int64(-25), m.Mul("-5", 5))
-	assert.Equal(t, int64(28), m.Mul(14, "2"))
-	assert.InEpsilon(t, float64(0.5), m.Mul("-1", -0.5), 1e-12)
+
+	actual, err := m.Mul(1, 1, 2, 3, 5)
+	require.NoError(t, err)
+	assert.Equal(t, int64(30), actual)
+
+	actual, err = m.Mul(1, 1)
+	require.NoError(t, err)
+	assert.Equal(t, int64(1), actual)
+
+	actual, err = m.Mul(1)
+	require.NoError(t, err)
+	assert.Equal(t, int64(1), actual)
+
+	actual, err = m.Mul("-5", 5)
+	require.NoError(t, err)
+	assert.Equal(t, int64(-25), actual)
+
+	actual, err = m.Mul(14, "2")
+	require.NoError(t, err)
+	assert.Equal(t, int64(28), actual)
+
+	actual, err = m.Mul("-1", -0.5)
+	require.NoError(t, err)
+	assert.InEpsilon(t, float64(0.5), actual, 1e-12)
 }
 
 func TestSub(t *testing.T) {
 	t.Parallel()
 
 	m := MathFuncs{}
-	assert.Equal(t, int64(0), m.Sub(1, 1))
-	assert.Equal(t, int64(-10), m.Sub(-5, 5))
-	assert.Equal(t, int64(-41), m.Sub(true, "42"))
-	assert.InEpsilon(t, -5.3, m.Sub(10, 15.3), 1e-12)
+
+	actual, err := m.Sub(1, 1)
+	require.NoError(t, err)
+	assert.Equal(t, int64(0), actual)
+
+	actual, err = m.Sub(-5, 5)
+	require.NoError(t, err)
+	assert.Equal(t, int64(-10), actual)
+
+	actual, err = m.Sub(true, "42")
+	require.NoError(t, err)
+	assert.Equal(t, int64(-41), actual)
+
+	actual, err = m.Sub(10, 15.3)
+	require.NoError(t, err)
+	assert.InEpsilon(t, -5.3, actual, 1e-12)
 }
 
 func mustDiv(a, b interface{}) interface{} {
@@ -86,16 +131,28 @@ func TestRem(t *testing.T) {
 	t.Parallel()
 
 	m := MathFuncs{}
-	assert.Equal(t, int64(0), m.Rem(1, 1))
-	assert.Equal(t, int64(2), m.Rem(5, 3.0))
+
+	actual, err := m.Rem(1, 1)
+	require.NoError(t, err)
+	assert.Equal(t, int64(0), actual)
+
+	actual, err = m.Rem(5, 3.0)
+	require.NoError(t, err)
+	assert.Equal(t, int64(2), actual)
 }
 
 func TestPow(t *testing.T) {
 	t.Parallel()
 
 	m := MathFuncs{}
-	assert.Equal(t, int64(4), m.Pow(2, "2"))
-	assert.InEpsilon(t, 2.25, m.Pow(1.5, 2), 1e-12)
+
+	actual, err := m.Pow(2, "2")
+	require.NoError(t, err)
+	assert.Equal(t, int64(4), actual)
+
+	actual, err = m.Pow(1.5, 2)
+	require.NoError(t, err)
+	assert.InEpsilon(t, 2.25, actual, 1e-12)
 }
 
 func mustSeq(t *testing.T, n ...interface{}) []int64 {
@@ -161,6 +218,7 @@ func TestIsIntFloatNum(t *testing.T) {
 		{nil, false, false},
 		{true, false, false},
 	}
+
 	m := MathFuncs{}
 	for _, tt := range tests {
 		tt := tt
@@ -178,6 +236,7 @@ func BenchmarkIsFloat(b *testing.B) {
 	data := []interface{}{
 		0, 1, -1, uint(42), uint8(255), uint16(42), uint32(42), uint64(42), int(42), int8(127), int16(42), int32(42), int64(42), float32(18.3), float64(18.3), 1.5, -18.6, "42", "052", "0xff", "-42", "-0", "3.14", "-3.14", "0.00", "NaN", "-Inf", "+Inf", "", "foo", nil, true,
 	}
+
 	m := MathFuncs{}
 	for _, n := range data {
 		n := n
@@ -197,9 +256,7 @@ func TestMax(t *testing.T) {
 		expected interface{}
 		n        []interface{}
 	}{
-		{int64(0), []interface{}{nil}},
 		{int64(0), []interface{}{0}},
-		{int64(0), []interface{}{"not a number"}},
 		{int64(1), []interface{}{1}},
 		{int64(-1), []interface{}{-1}},
 		{int64(1), []interface{}{-1, 0, 1}},
@@ -220,6 +277,19 @@ func TestMax(t *testing.T) {
 			assert.Equal(t, d.expected, actual)
 		})
 	}
+
+	t.Run("error cases", func(t *testing.T) {
+		t.Parallel()
+
+		_, err := m.Max("foo")
+		require.Error(t, err)
+
+		_, err = m.Max(nil)
+		require.Error(t, err)
+
+		_, err = m.Max("")
+		require.Error(t, err)
+	})
 }
 
 func TestMin(t *testing.T) {
@@ -230,9 +300,7 @@ func TestMin(t *testing.T) {
 		expected interface{}
 		n        []interface{}
 	}{
-		{int64(0), []interface{}{nil}},
 		{int64(0), []interface{}{0}},
-		{int64(0), []interface{}{"not a number"}},
 		{int64(1), []interface{}{1}},
 		{int64(-1), []interface{}{-1}},
 		{int64(-1), []interface{}{-1, 0, 1}},
@@ -250,9 +318,23 @@ func TestMin(t *testing.T) {
 			} else {
 				actual, _ = m.Min(d.n[0], d.n[1:]...)
 			}
+
 			assert.Equal(t, d.expected, actual)
 		})
 	}
+
+	t.Run("error cases", func(t *testing.T) {
+		t.Parallel()
+
+		_, err := m.Min("foo")
+		require.Error(t, err)
+
+		_, err = m.Min(nil)
+		require.Error(t, err)
+
+		_, err = m.Min("")
+		require.Error(t, err)
+	})
 }
 
 func TestContainsFloat(t *testing.T) {
@@ -297,8 +379,6 @@ func TestCeil(t *testing.T) {
 		n interface{}
 		a float64
 	}{
-		{"", 0.},
-		{nil, 0.},
 		{"Inf", gmath.Inf(1)},
 		{0, 0.},
 		{4.99, 5.},
@@ -310,9 +390,24 @@ func TestCeil(t *testing.T) {
 		t.Run(fmt.Sprintf("%v==%v", d.n, d.a), func(t *testing.T) {
 			t.Parallel()
 
-			assert.InDelta(t, d.a, m.Ceil(d.n), 1e-12)
+			actual, err := m.Ceil(d.n)
+			require.NoError(t, err)
+			assert.InDelta(t, d.a, actual, 1e-12)
 		})
 	}
+
+	t.Run("error cases", func(t *testing.T) {
+		t.Parallel()
+
+		_, err := m.Ceil("foo")
+		require.Error(t, err)
+
+		_, err = m.Ceil(nil)
+		require.Error(t, err)
+
+		_, err = m.Ceil("")
+		require.Error(t, err)
+	})
 }
 
 func TestFloor(t *testing.T) {
@@ -323,8 +418,6 @@ func TestFloor(t *testing.T) {
 		n interface{}
 		a float64
 	}{
-		{"", 0.},
-		{nil, 0.},
 		{"Inf", gmath.Inf(1)},
 		{0, 0.},
 		{4.99, 4.},
@@ -336,9 +429,24 @@ func TestFloor(t *testing.T) {
 		t.Run(fmt.Sprintf("%v==%v", d.n, d.a), func(t *testing.T) {
 			t.Parallel()
 
-			assert.InDelta(t, d.a, m.Floor(d.n), 1e-12)
+			actual, err := m.Floor(d.n)
+			require.NoError(t, err)
+			assert.InDelta(t, d.a, actual, 1e-12)
 		})
 	}
+
+	t.Run("error cases", func(t *testing.T) {
+		t.Parallel()
+
+		_, err := m.Floor("foo")
+		require.Error(t, err)
+
+		_, err = m.Floor(nil)
+		require.Error(t, err)
+
+		_, err = m.Floor("")
+		require.Error(t, err)
+	})
 }
 
 func TestRound(t *testing.T) {
@@ -349,8 +457,6 @@ func TestRound(t *testing.T) {
 		n interface{}
 		a float64
 	}{
-		{"", 0.},
-		{nil, 0.},
 		{"Inf", gmath.Inf(1)},
 		{0, 0.},
 		{4.99, 5},
@@ -366,9 +472,24 @@ func TestRound(t *testing.T) {
 		t.Run(fmt.Sprintf("%v==%v", d.n, d.a), func(t *testing.T) {
 			t.Parallel()
 
-			assert.InDelta(t, d.a, m.Round(d.n), 1e-12)
+			actual, err := m.Round(d.n)
+			require.NoError(t, err)
+			assert.InDelta(t, d.a, actual, 1e-12)
 		})
 	}
+
+	t.Run("error cases", func(t *testing.T) {
+		t.Parallel()
+
+		_, err := m.Round("foo")
+		require.Error(t, err)
+
+		_, err = m.Round(nil)
+		require.Error(t, err)
+
+		_, err = m.Round("")
+		require.Error(t, err)
+	})
 }
 
 func TestAbs(t *testing.T) {
@@ -379,8 +500,6 @@ func TestAbs(t *testing.T) {
 		n interface{}
 		a interface{}
 	}{
-		{"", 0.},
-		{nil, 0.},
 		{"-Inf", gmath.Inf(1)},
 		{0, int64(0)},
 		{0., 0.},
@@ -395,7 +514,22 @@ func TestAbs(t *testing.T) {
 		t.Run(fmt.Sprintf("%#v==%v", d.n, d.a), func(t *testing.T) {
 			t.Parallel()
 
-			assert.Equal(t, d.a, m.Abs(d.n))
+			actual, err := m.Abs(d.n)
+			require.NoError(t, err)
+			assert.Equal(t, d.a, actual)
 		})
 	}
+
+	t.Run("error cases", func(t *testing.T) {
+		t.Parallel()
+
+		_, err := m.Abs("foo")
+		require.Error(t, err)
+
+		_, err = m.Abs(nil)
+		require.Error(t, err)
+
+		_, err = m.Abs("")
+		require.Error(t, err)
+	})
 }
diff --git a/internal/funcs/net.go b/internal/funcs/net.go
index bf8a2674..9f69579a 100644
--- a/internal/funcs/net.go
+++ b/internal/funcs/net.go
@@ -132,7 +132,12 @@ func (f *NetFuncs) CIDRHost(hostnum interface{}, prefix interface{}) (netip.Addr
 		return netip.Addr{}, err
 	}
 
-	ip, err := cidr.HostBig(network, big.NewInt(conv.ToInt64(hostnum)))
+	n, err := conv.ToInt64(hostnum)
+	if err != nil {
+		return netip.Addr{}, fmt.Errorf("expected a number: %w", err)
+	}
+
+	ip, err := cidr.HostBig(network, big.NewInt(n))
 
 	return ip, err
 }
@@ -175,7 +180,11 @@ func (f *NetFuncs) CIDRSubnets(newbits interface{}, prefix interface{}) ([]netip
 		return nil, err
 	}
 
-	nBits := conv.ToInt(newbits)
+	nBits, err := conv.ToInt(newbits)
+	if err != nil {
+		return nil, fmt.Errorf("newbits must be a number: %w", err)
+	}
+
 	if nBits < 1 {
 		return nil, fmt.Errorf("must extend prefix by at least one bit")
 	}
@@ -208,7 +217,11 @@ func (f *NetFuncs) CIDRSubnetSizes(args ...interface{}) ([]netip.Prefix, error)
 	if err != nil {
 		return nil, err
 	}
-	newbits := conv.ToInts(args[:len(args)-1]...)
+
+	newbits, err := conv.ToInts(args[:len(args)-1]...)
+	if err != nil {
+		return nil, fmt.Errorf("newbits must be numbers: %w", err)
+	}
 
 	startPrefixLen := network.Bits()
 	firstLength := newbits[0]
diff --git a/internal/funcs/random.go b/internal/funcs/random.go
index 84bad8d7..0f18ae92 100644
--- a/internal/funcs/random.go
+++ b/internal/funcs/random.go
@@ -26,25 +26,45 @@ type RandomFuncs struct {
 
 // ASCII -
 func (RandomFuncs) ASCII(count interface{}) (string, error) {
-	return random.StringBounds(conv.ToInt(count), ' ', '~')
+	n, err := conv.ToInt(count)
+	if err != nil {
+		return "", fmt.Errorf("count must be an integer: %w", err)
+	}
+
+	return random.StringBounds(n, ' ', '~')
 }
 
 // Alpha -
 func (RandomFuncs) Alpha(count interface{}) (string, error) {
-	return random.StringRE(conv.ToInt(count), "[[:alpha:]]")
+	n, err := conv.ToInt(count)
+	if err != nil {
+		return "", fmt.Errorf("count must be an integer: %w", err)
+	}
+
+	return random.StringRE(n, "[[:alpha:]]")
 }
 
 // AlphaNum -
 func (RandomFuncs) AlphaNum(count interface{}) (string, error) {
-	return random.StringRE(conv.ToInt(count), "[[:alnum:]]")
+	n, err := conv.ToInt(count)
+	if err != nil {
+		return "", fmt.Errorf("count must be an integer: %w", err)
+	}
+
+	return random.StringRE(n, "[[:alnum:]]")
 }
 
 // String -
-func (RandomFuncs) String(count interface{}, args ...interface{}) (s string, err error) {
-	c := conv.ToInt(count)
+func (RandomFuncs) String(count interface{}, args ...interface{}) (string, error) {
+	c, err := conv.ToInt(count)
+	if err != nil {
+		return "", fmt.Errorf("count must be an integer: %w", err)
+	}
+
 	if c == 0 {
 		return "", fmt.Errorf("count must be greater than 0")
 	}
+
 	m := ""
 	switch len(args) {
 	case 0:
@@ -59,8 +79,17 @@ func (RandomFuncs) String(count interface{}, args ...interface{}) (s string, err
 				return "", err
 			}
 		} else {
-			l = rune(conv.ToInt(args[0]))
-			u = rune(conv.ToInt(args[1]))
+			nl, err := conv.ToInt(args[0])
+			if err != nil {
+				return "", fmt.Errorf("lower must be an integer: %w", err)
+			}
+
+			nu, err := conv.ToInt(args[1])
+			if err != nil {
+				return "", fmt.Errorf("upper must be an integer: %w", err)
+			}
+
+			l, u = rune(nl), rune(nu)
 		}
 
 		return random.StringBounds(c, l, u)
@@ -114,14 +143,28 @@ func (RandomFuncs) Item(items interface{}) (interface{}, error) {
 func (RandomFuncs) Number(args ...interface{}) (int64, error) {
 	var min, max int64
 	min, max = 0, 100
+
+	var err error
+
 	switch len(args) {
 	case 0:
 	case 1:
-		max = conv.ToInt64(args[0])
+		max, err = conv.ToInt64(args[0])
+		if err != nil {
+			return 0, fmt.Errorf("max must be a number: %w", err)
+		}
 	case 2:
-		min = conv.ToInt64(args[0])
-		max = conv.ToInt64(args[1])
+		min, err = conv.ToInt64(args[0])
+		if err != nil {
+			return 0, fmt.Errorf("min must be a number: %w", err)
+		}
+
+		max, err = conv.ToInt64(args[1])
+		if err != nil {
+			return 0, fmt.Errorf("max must be a number: %w", err)
+		}
 	}
+
 	return random.Number(min, max)
 }
 
@@ -129,13 +172,27 @@ func (RandomFuncs) Number(args ...interface{}) (int64, error) {
 func (RandomFuncs) Float(args ...interface{}) (float64, error) {
 	var min, max float64
 	min, max = 0, 1.0
+
+	var err error
+
 	switch len(args) {
 	case 0:
 	case 1:
-		max = conv.ToFloat64(args[0])
+		max, err = conv.ToFloat64(args[0])
+		if err != nil {
+			return 0, fmt.Errorf("max must be a number: %w", err)
+		}
 	case 2:
-		min = conv.ToFloat64(args[0])
-		max = conv.ToFloat64(args[1])
+		min, err = conv.ToFloat64(args[0])
+		if err != nil {
+			return 0, fmt.Errorf("min must be a number: %w", err)
+		}
+
+		max, err = conv.ToFloat64(args[1])
+		if err != nil {
+			return 0, fmt.Errorf("max must be a number: %w", err)
+		}
 	}
+
 	return random.Float(min, max)
 }
diff --git a/internal/funcs/regexp.go b/internal/funcs/regexp.go
index 49bafd1c..d7f6a685 100644
--- a/internal/funcs/regexp.go
+++ b/internal/funcs/regexp.go
@@ -31,6 +31,7 @@ func (ReFuncs) FindAll(args ...interface{}) ([]string, error) {
 	re := ""
 	n := 0
 	input := ""
+
 	switch len(args) {
 	case 2:
 		n = -1
@@ -38,11 +39,18 @@ func (ReFuncs) FindAll(args ...interface{}) ([]string, error) {
 		input = conv.ToString(args[1])
 	case 3:
 		re = conv.ToString(args[0])
-		n = conv.ToInt(args[1])
+
+		var err error
+		n, err = conv.ToInt(args[1])
+		if err != nil {
+			return nil, fmt.Errorf("n must be an integer: %w", err)
+		}
+
 		input = conv.ToString(args[2])
 	default:
 		return nil, fmt.Errorf("wrong number of args: want 2 or 3, got %d", len(args))
 	}
+
 	return regexp.FindAll(re, n, input)
 }
 
@@ -75,16 +83,23 @@ func (ReFuncs) Split(args ...interface{}) ([]string, error) {
 	re := ""
 	n := -1
 	input := ""
+
 	switch len(args) {
 	case 2:
 		re = conv.ToString(args[0])
 		input = conv.ToString(args[1])
 	case 3:
 		re = conv.ToString(args[0])
-		n = conv.ToInt(args[1])
+		var err error
+		n, err = conv.ToInt(args[1])
+		if err != nil {
+			return nil, fmt.Errorf("n must be an integer: %w", err)
+		}
+
 		input = conv.ToString(args[2])
 	default:
 		return nil, fmt.Errorf("wrong number of args: want 2 or 3, got %d", len(args))
 	}
+
 	return regexp.Split(re, n, input)
 }
diff --git a/internal/funcs/strings.go b/internal/funcs/strings.go
index 53869c7b..cb440868 100644
--- a/internal/funcs/strings.go
+++ b/internal/funcs/strings.go
@@ -115,23 +115,39 @@ func (f *StringFuncs) oldTrim(s, cutset string) string {
 func (StringFuncs) Abbrev(args ...interface{}) (string, error) {
 	str := ""
 	offset := 0
-	maxWidth := 0
-	if len(args) < 2 {
-		return "", fmt.Errorf("abbrev requires a 'maxWidth' and 'input' argument")
-	}
-	if len(args) == 2 {
-		maxWidth = conv.ToInt(args[0])
+	width := 0
+
+	var err error
+
+	switch len(args) {
+	case 2:
+		width, err = conv.ToInt(args[0])
+		if err != nil {
+			return "", fmt.Errorf("width must be an integer: %w", err)
+		}
+
 		str = conv.ToString(args[1])
-	}
-	if len(args) == 3 {
-		offset = conv.ToInt(args[0])
-		maxWidth = conv.ToInt(args[1])
+	case 3:
+		offset, err = conv.ToInt(args[0])
+		if err != nil {
+			return "", fmt.Errorf("offset must be an integer: %w", err)
+		}
+
+		width, err = conv.ToInt(args[1])
+		if err != nil {
+			return "", fmt.Errorf("width must be an integer: %w", err)
+		}
+
 		str = conv.ToString(args[2])
+	default:
+		return "", fmt.Errorf("abbrev requires a 'width' and 'input' argument")
 	}
-	if len(str) <= maxWidth {
+
+	if len(str) <= width {
 		return str, nil
 	}
-	return goutils.AbbreviateFull(str, offset, maxWidth)
+
+	return goutils.AbbreviateFull(str, offset, width)
 }
 
 // ReplaceAll -
@@ -342,13 +358,25 @@ func (StringFuncs) WordWrap(args ...interface{}) (string, error) {
 		case string:
 			opts.LBSeq = a
 		default:
-			opts.Width = uint(conv.ToInt(a))
+			n, err := conv.ToInt(args[0])
+			if err != nil {
+				return "", fmt.Errorf("expected width to be a number: %w", err)
+			}
+
+			opts.Width = uint(n)
 		}
 	}
+
 	if len(args) == 3 {
-		opts.Width = uint(conv.ToInt(args[0]))
+		n, err := conv.ToInt(args[0])
+		if err != nil {
+			return "", fmt.Errorf("expected width to be a number: %w", err)
+		}
+
+		opts.Width = uint(n)
 		opts.LBSeq = conv.ToString(args[1])
 	}
+
 	return gompstrings.WordWrap(in, opts), nil
 }
 
diff --git a/internal/funcs/time.go b/internal/funcs/time.go
index deaddc2e..532335c3 100644
--- a/internal/funcs/time.go
+++ b/internal/funcs/time.go
@@ -104,33 +104,63 @@ func (TimeFuncs) Unix(in interface{}) (gotime.Time, error) {
 }
 
 // Nanosecond -
-func (TimeFuncs) Nanosecond(n interface{}) gotime.Duration {
-	return gotime.Nanosecond * gotime.Duration(conv.ToInt64(n))
+func (TimeFuncs) Nanosecond(n interface{}) (gotime.Duration, error) {
+	in, err := conv.ToInt64(n)
+	if err != nil {
+		return 0, fmt.Errorf("expected a number: %w", err)
+	}
+
+	return gotime.Nanosecond * gotime.Duration(in), nil
 }
 
 // Microsecond -
-func (TimeFuncs) Microsecond(n interface{}) gotime.Duration {
-	return gotime.Microsecond * gotime.Duration(conv.ToInt64(n))
+func (TimeFuncs) Microsecond(n interface{}) (gotime.Duration, error) {
+	in, err := conv.ToInt64(n)
+	if err != nil {
+		return 0, fmt.Errorf("expected a number: %w", err)
+	}
+
+	return gotime.Microsecond * gotime.Duration(in), nil
 }
 
 // Millisecond -
-func (TimeFuncs) Millisecond(n interface{}) gotime.Duration {
-	return gotime.Millisecond * gotime.Duration(conv.ToInt64(n))
+func (TimeFuncs) Millisecond(n interface{}) (gotime.Duration, error) {
+	in, err := conv.ToInt64(n)
+	if err != nil {
+		return 0, fmt.Errorf("expected a number: %w", err)
+	}
+
+	return gotime.Millisecond * gotime.Duration(in), nil
 }
 
 // Second -
-func (TimeFuncs) Second(n interface{}) gotime.Duration {
-	return gotime.Second * gotime.Duration(conv.ToInt64(n))
+func (TimeFuncs) Second(n interface{}) (gotime.Duration, error) {
+	in, err := conv.ToInt64(n)
+	if err != nil {
+		return 0, fmt.Errorf("expected a number: %w", err)
+	}
+
+	return gotime.Second * gotime.Duration(in), nil
 }
 
 // Minute -
-func (TimeFuncs) Minute(n interface{}) gotime.Duration {
-	return gotime.Minute * gotime.Duration(conv.ToInt64(n))
+func (TimeFuncs) Minute(n interface{}) (gotime.Duration, error) {
+	in, err := conv.ToInt64(n)
+	if err != nil {
+		return 0, fmt.Errorf("expected a number: %w", err)
+	}
+
+	return gotime.Minute * gotime.Duration(in), nil
 }
 
 // Hour -
-func (TimeFuncs) Hour(n interface{}) gotime.Duration {
-	return gotime.Hour * gotime.Duration(conv.ToInt64(n))
+func (TimeFuncs) Hour(n interface{}) (gotime.Duration, error) {
+	in, err := conv.ToInt64(n)
+	if err != nil {
+		return 0, fmt.Errorf("expected a number: %w", err)
+	}
+
+	return gotime.Hour * gotime.Duration(in), nil
 }
 
 // ParseDuration -
diff --git a/internal/tests/integration/math_test.go b/internal/tests/integration/math_test.go
index 769cae46..b3289b28 100644
--- a/internal/tests/integration/math_test.go
+++ b/internal/tests/integration/math_test.go
@@ -13,8 +13,9 @@ func TestMath(t *testing.T) {
 	inOutTest(t, `{{ math.Pow 8 4 }} {{ pow 2 2 }}`, "4096 4")
 	inOutTest(t, `{{ math.Seq 0 }}, {{ seq 0 3 }}, {{ seq -5 -10 2 }}`,
 		`[1 0], [0 1 2 3], [-5 -7 -9]`)
-	inOutTest(t, `{{ math.Round 0.99 }}, {{ math.Round "foo" }}, {{math.Round 3.5}}`,
-		`1, 0, 4`)
+	inOutTest(t, `{{ math.Round 0.99 }}, {{math.Round 3.5}}`, `1, 4`)
 	inOutTest(t, `{{ math.Max -0 "+Inf" "NaN" }}, {{ math.Max 3.4 3.401 3.399 }}`,
 		`+Inf, 3.401`)
+
+	inOutContainsError(t, `{{ math.Round "foo" }}`, `could not convert \"foo\"`)
 }