luzer: fix parsing command-line flags

The patch fixes a problem with incorrect parsing command-line
flags and adds a tests for the function `parse_flag()`.

Fixes #23

Author: ligurio

luzer/init.lua

@@ -14,7 +14,7 @@ end
 --
 -- 1. https://llvm.org/docs/LibFuzzer.html#options
 local function parse_flag(str)
-    local flag_name, flag_val = string.match(str, "-([%l%p]+)=(%w+)")
+    local flag_name, flag_val = string.match(str, "-([%w_]+)=(.+)")
     if not flag_name or
        not flag_val then
         error(("bad flag: %s"):format(str))
@@ -58,4 +58,8 @@ return {
 
     _set_custom_mutator = luzer_impl._set_custom_mutator,
     _mutate = luzer_impl._mutate,
+
+    internal = {
+        parse_flag = parse_flag,
+    }
 }

luzer/tests/test_unit.lua

@@ -200,4 +200,22 @@ assert(luzer_custom_mutator ~= nil)
 -- luzer._mutate(buf, #buf, #buf, math.random(1, 10)) -- TODO
 luzer_custom_mutator = nil -- Clean up.
 
+-- luzer.internal.parse_flag()
+local flag_testcases = {
+    { "dict", "/tmp/lua.dict" },
+    { "help", "1" },
+    { "rss_limit_mb", "2048" },
+    { "runs", "-1" },
+}
+for _, testcase in ipairs(flag_testcases) do
+    local name = testcase[1]
+    local val = testcase[2]
+    -- libFuzzer flags are strictly in form `-flag=value`.
+    local flag = ("-%s=%s"):format(name, val)
+    -- Expected a table with `name` and `value`.
+    res = { luzer.internal.parse_flag(flag) }
+    assert(name == res[1], ("expected %s"):format(name))
+    assert(val == res[2], ("expected %s"):format(val))
+end
+
 print("Success!")