feat: add trim_left and trim_right functions

These functions trim characters from the left or right side of a string.
They take a character set (not a literal substring) and remove all
matching characters from the specified side.

Examples:
  trim_left("aaabbb", "a")    → "bbb" (all 'a's removed from left)
  trim_right("aaabbb", "b")   → "aaa" (all 'b's removed from right)
  trim_left("  hello  ")      → "hello  " (whitespace from left)

When no second argument is provided, they default to trimming
whitespace.

As of this commit, they behave exactly like trim_prefix and trim_suffix,
but we're about to change these to work specifically on literal
prefix/suffixes.

Author: amterp

core/funcs.go

@@ -91,6 +91,8 @@ const (
 	FUNC_TRIM               = "trim"
 	FUNC_TRIM_PREFIX        = "trim_prefix"
 	FUNC_TRIM_SUFFIX        = "trim_suffix"
+	FUNC_TRIM_LEFT          = "trim_left"
+	FUNC_TRIM_RIGHT         = "trim_right"
 	FUNC_READ_FILE          = "read_file"
 	FUNC_WRITE_FILE         = "write_file"
 	FUNC_READ_STDIN         = "read_stdin"
@@ -1035,6 +1037,22 @@ func init() {
 				})
 			},
 		},
+		{
+			Name: FUNC_TRIM_LEFT,
+			Execute: func(f FuncInvocation) RadValue {
+				return runTrim(f, func(str RadString, chars string) RadString {
+					return str.TrimLeft(chars)
+				})
+			},
+		},
+		{
+			Name: FUNC_TRIM_RIGHT,
+			Execute: func(f FuncInvocation) RadValue {
+				return runTrim(f, func(str RadString, chars string) RadString {
+					return str.TrimRight(chars)
+				})
+			},
+		},
 		{
 			// todo potential additional named args
 			//   - encoding="utf-8", # Or null for raw bytes
@@ -1928,9 +1946,9 @@ func httpMethodFromFuncName(httpFunc string) string {
 
 func runTrim(f FuncInvocation, trimFunc func(str RadString, chars string) RadString) RadValue {
 	subject := f.GetStr("_subject")
-	toTrim := f.GetStr("_to_trim").Plain()
+	chars := f.GetStr("_chars").Plain()
 
-	subject = trimFunc(subject, toTrim)
+	subject = trimFunc(subject, chars)
 	return f.Return(subject)
 }
 

core/testing/func_trim_left_test.go

@@ -0,0 +1,30 @@
+package testing
+
+import "testing"
+
+func Test_Func_Trim_Left_SingleChar(t *testing.T) {
+	script := `
+print(trim_left("aaabbb", "a"))
+`
+	setupAndRunCode(t, script, "--color=never")
+	assertOnlyOutput(t, stdOutBuffer, "bbb\n") // ALL "a"s removed
+	assertNoErrors(t)
+}
+
+func Test_Func_Trim_Left_MultiChar(t *testing.T) {
+	script := `
+print(trim_left(",,!!,hello,!,", "!,"))
+`
+	setupAndRunCode(t, script, "--color=never")
+	assertOnlyOutput(t, stdOutBuffer, "hello,!,\n")
+	assertNoErrors(t)
+}
+
+func Test_Func_Trim_Left_NoArg_Whitespace(t *testing.T) {
+	script := `
+print(trim_left("  hello  "))
+`
+	setupAndRunCode(t, script, "--color=never")
+	assertOnlyOutput(t, stdOutBuffer, "hello  \n")
+	assertNoErrors(t)
+}

core/testing/func_trim_right_test.go

@@ -0,0 +1,30 @@
+package testing
+
+import "testing"
+
+func Test_Func_Trim_Right_SingleChar(t *testing.T) {
+	script := `
+print(trim_right("aaabbb", "b"))
+`
+	setupAndRunCode(t, script, "--color=never")
+	assertOnlyOutput(t, stdOutBuffer, "aaa\n") // ALL "b"s removed
+	assertNoErrors(t)
+}
+
+func Test_Func_Trim_Right_MultiChar(t *testing.T) {
+	script := `
+print(trim_right(",,!!,hello,!,", "!,"))
+`
+	setupAndRunCode(t, script, "--color=never")
+	assertOnlyOutput(t, stdOutBuffer, ",,!!,hello\n")
+	assertNoErrors(t)
+}
+
+func Test_Func_Trim_Right_NoArg_Whitespace(t *testing.T) {
+	script := `
+print(trim_right("  hello  "))
+`
+	setupAndRunCode(t, script, "--color=never")
+	assertOnlyOutput(t, stdOutBuffer, "  hello\n")
+	assertNoErrors(t)
+}

core/type_string.go

@@ -213,6 +213,16 @@ func (s *RadString) TrimSuffix(suffix string) RadString {
 	return NewRadString(strings.TrimRight(s.Plain(), suffix))
 }
 
+func (s *RadString) TrimLeft(chars string) RadString {
+	// todo should maintain attr info
+	return NewRadString(strings.TrimLeft(s.Plain(), chars))
+}
+
+func (s *RadString) TrimRight(chars string) RadString {
+	// todo should maintain attr info
+	return NewRadString(strings.TrimRight(s.Plain(), chars))
+}
+
 func (s *RadString) Reverse() RadString {
 	// todo should maintain attr info
 	return NewRadString(com.Reverse(s.Plain()))

rts/embedded/functions.txt

@@ -92,7 +92,9 @@ starts_with
 str
 sum
 trim
+trim_left
 trim_prefix
+trim_right
 trim_suffix
 truncate
 type_of

rts/signatures.go

@@ -80,6 +80,8 @@ func init() {
 		newFnSignature(`trim(_subject: str, _to_trim: str = " \t\n") -> str`),
 		newFnSignature(`trim_prefix(_subject: str, _to_trim: str = " \t\n") -> str`),
 		newFnSignature(`trim_suffix(_subject: str, _to_trim: str = " \t\n") -> str`),
+		newFnSignature(`trim_left(_subject: str, _to_trim: str = " \t\n") -> str`),
+		newFnSignature(`trim_right(_subject: str, _to_trim: str = " \t\n") -> str`),
 		newFnSignature(`read_file(_path: str, *, mode: ["text", "bytes"] = "text") -> error|{ "size_bytes": int, "content": str|int[] }`),
 		newFnSignature(`write_file(_path: str, _content: str, *, append: bool = false) -> error|{ "bytes_written": int, "path": str }`),
 		newFnSignature(`read_stdin() -> str?|error`),