starlark: int: ignore base prefix unless matches explicit base

Previously, when int was called with an explicit base,
it would report an error if the digit string starts
with a base prefix for a different base, such as int("0b101", 16).
Now, it uses the base prefix only if it matches the requested
base, so the example above would return 0x0b101, as would
int("0x0b101", 16).

See github.com/google/starlark-go/pull/344

PiperOrigin-RevId: 355479386

src/main/java/net/starlark/java/eval/StarlarkInt.java

@@ -121,14 +121,9 @@ public static StarlarkInt parse(String s, int base) {
         prefixBase = 16;
       }
       if (prefixBase != 0) {
-        digits = s.substring(2); // strip prefix
-        if (base == 0) {
+        if (base == 0 || base == prefixBase) {
           base = prefixBase;
-        } else if (base != prefixBase) {
-          throw new NumberFormatException(
-              String.format(
-                  "invalid base-%d literal: %s (%s prefix wants base %d)",
-                  base, Starlark.repr(stringForErrors), s.substring(0, 2), prefixBase));
+          digits = s.substring(2); // strip prefix
         }
       }
     }

src/test/java/net/starlark/java/eval/testdata/int_constructor.star

@@ -20,50 +20,52 @@ assert_fails(lambda: int(None), "got NoneType, want string, int, float, or bool"
 assert_fails(lambda: int(""), "empty string")
 
 # no base
-assert_eq(int('0'), 0)
-assert_eq(int('1'), 1)
-assert_eq(int('42'), 42)
-assert_eq(int('-1'), -1)
-assert_eq(int('-1234'), -1234)
-assert_eq(int('2147483647'), 2147483647)
-assert_eq(int('-2147483648'), -2147483647 - 1)
-assert_eq(int('123456789012345678901234567891234567890'), 123456789012345678901234567891234567890)
-assert_eq(int('-123456789012345678901234567891234567890'), -123456789012345678901234567891234567890)
-assert_eq(int('-0xabcdefabcdefabcdefabcdefabcdef', 0), -0xabcdefabcdefabcdefabcdefabcdef)
-assert_eq(int('1111111111111', 2), 8191)
-assert_eq(int('1111111111111', 5), 305175781)
-assert_eq(int('1111111111111', 8), 78536544841)
-assert_eq(int('1111111111111', 10), 1111111111111)
-assert_eq(int('1111111111111', 16), 300239975158033)
-assert_eq(int('1111111111111', 36), 4873763662273663093)
-assert_eq(int('016'), 16) # zero ok when base != 0.
-assert_eq(int('+42'), 42) # '+' prefix ok
+assert_eq(int("0"), 0)
+assert_eq(int("1"), 1)
+assert_eq(int("42"), 42)
+assert_eq(int("-1"), -1)
+assert_eq(int("-1234"), -1234)
+assert_eq(int("2147483647"), 2147483647)
+assert_eq(int("-2147483648"), -2147483647 - 1)
+assert_eq(int("123456789012345678901234567891234567890"), 123456789012345678901234567891234567890)
+assert_eq(int("-123456789012345678901234567891234567890"), -123456789012345678901234567891234567890)
+assert_eq(int("-0xabcdefabcdefabcdefabcdefabcdef", 0), -0xabcdefabcdefabcdefabcdefabcdef)
+assert_eq(int("1111111111111", 2), 8191)
+assert_eq(int("1111111111111", 5), 305175781)
+assert_eq(int("1111111111111", 8), 78536544841)
+assert_eq(int("1111111111111", 10), 1111111111111)
+assert_eq(int("1111111111111", 16), 300239975158033)
+assert_eq(int("1111111111111", 36), 4873763662273663093)
+assert_eq(int("016"), 16)  # zero ok when base != 0.
+assert_eq(int("+42"), 42)  # '+' prefix ok
+
 # with base, no prefix
-assert_eq(int('11', 2), 3)
-assert_eq(int('11', 9), 10)
-assert_eq(int('AF', 16), 175)
-assert_eq(int('11', 36), 37)
-assert_eq(int('az', 36), 395)
-assert_eq(int('11', 10), 11)
-assert_eq(int('11', 0), 11)
+assert_eq(int("11", 2), 3)
+assert_eq(int("11", 9), 10)
+assert_eq(int("AF", 16), 175)
+assert_eq(int("11", 36), 37)
+assert_eq(int("az", 36), 395)
+assert_eq(int("11", 10), 11)
+assert_eq(int("11", 0), 11)
+
 # base and prefix
-assert_eq(int('0b11', 0), 3)
-assert_eq(int('0B11', 2), 3)
-assert_eq(int('0o11', 0), 9)
-assert_eq(int('0O11', 8), 9)
-assert_eq(int('0XFF', 0), 255)
-assert_eq(int('0xFF', 16), 255)
-assert_eq(int('0b11', 0), 3)
-assert_eq(int('-0b11', 0), -3)
-assert_eq(int('+0b11', 0), 3)
-assert_eq(int('0B11', 2), 3)
-assert_eq(int('0o11', 0), 9)
-assert_eq(int('0O11', 8), 9)
-assert_eq(int('-11', 2), -3)
-assert_eq(int('016', 8), 14)
-assert_eq(int('016', 16), 22)
-assert_eq(int('0', 0), 0)
-assert_eq(int('0x0b10', 16), 0x0b10)
+assert_eq(int("0b11", 0), 3)
+assert_eq(int("0B11", 2), 3)
+assert_eq(int("0o11", 0), 9)
+assert_eq(int("0O11", 8), 9)
+assert_eq(int("0XFF", 0), 255)
+assert_eq(int("0xFF", 16), 255)
+assert_eq(int("0b11", 0), 3)
+assert_eq(int("-0b11", 0), -3)
+assert_eq(int("+0b11", 0), 3)
+assert_eq(int("0B11", 2), 3)
+assert_eq(int("0o11", 0), 9)
+assert_eq(int("0O11", 8), 9)
+assert_eq(int("-11", 2), -3)
+assert_eq(int("016", 8), 14)
+assert_eq(int("016", 16), 22)
+assert_eq(int("0", 0), 0)
+assert_eq(int("0x0b10", 16), 0x0b10)
 assert_fails(lambda: int("0xFF", 8), 'invalid base-8 literal: "0xFF"')
 assert_fails(lambda: int("016", 0), 'cannot infer base when string begins with a 0: "016"')
 assert_fails(lambda: int("123", 3), 'invalid base-3 literal: "123"')
@@ -76,16 +78,27 @@ assert_fails(lambda: int(True, 2), "can't convert non-string with explicit base"
 assert_fails(lambda: int(True, 10), "can't convert non-string with explicit base")
 assert_fails(lambda: int(1, 2), "can't convert non-string with explicit base")
 
+# Base prefix is honored only if base=0, or if the prefix matches the explicit base.
+# See https://github.com/google/starlark-go/issues/337
+assert_fails(lambda: int("0b0"), "invalid base-10 literal")
+assert_eq(int("0b0", 0), 0)
+assert_eq(int("0b0", 2), 0)
+assert_eq(int("0b0", 16), 0xb0)
+assert_eq(int("0x0b0", 16), 0xb0)
+assert_eq(int("0x0b0", 0), 0xb0)
+assert_eq(int("0x0b0101", 16), 0x0b0101)
+assert_eq(int("0b0101", 2), 5)  # prefix is redundant with explicit base
+
 # This case is allowed in Python but not Skylark
 assert_fails(lambda: int(), "missing 1 required positional argument: x")
 
 # Unlike Python, leading and trailing whitespace is not allowed. Use int(s.strip()).
-assert_fails(lambda: int(' 1'), 'invalid base-10 literal: " 1"')
-assert_fails(lambda: int('1 '), 'invalid base-10 literal: "1 "')
-assert_fails(lambda: int('-'), 'invalid base-10 literal: "-"')
-assert_fails(lambda: int('+'), 'invalid base-10 literal: "[+]"')
-assert_fails(lambda: int('0x'), 'invalid base-10 literal: "0x"')
-assert_fails(lambda: int('1.5'), 'invalid base-10 literal: "1.5"')
-assert_fails(lambda: int('ab'), 'invalid base-10 literal: "ab"')
-assert_fails(lambda: int('--1'), 'invalid base-10 literal: "--1"')
-assert_fails(lambda: int('-0x-10', 16), 'invalid base-16 literal: "-0x-10"')
+assert_fails(lambda: int(" 1"), 'invalid base-10 literal: " 1"')
+assert_fails(lambda: int("1 "), 'invalid base-10 literal: "1 "')
+assert_fails(lambda: int("-"), 'invalid base-10 literal: "-"')
+assert_fails(lambda: int("+"), 'invalid base-10 literal: "[+]"')
+assert_fails(lambda: int("0x"), 'invalid base-10 literal: "0x"')
+assert_fails(lambda: int("1.5"), 'invalid base-10 literal: "1.5"')
+assert_fails(lambda: int("ab"), 'invalid base-10 literal: "ab"')
+assert_fails(lambda: int("--1"), 'invalid base-10 literal: "--1"')
+assert_fails(lambda: int("-0x-10", 16), 'invalid base-16 literal: "-0x-10"')