Consistent use of ValueError when parsing settings. NFC (#21245)

This is in preparation for a change to avoid using json parsing for
settings by default.

It also adds more context to the errors since when the ValueError
is caught higher up we print nice error messages.

emcc.py

@@ -1457,7 +1457,8 @@ def parse_string_value(text):
     first = text[0]
     if first == "'" or first == '"':
       text = text.rstrip()
-      assert text[-1] == text[0] and len(text) > 1, 'unclosed opened quoted string. expected final character to be "%s" and length to be greater than 1 in "%s"' % (text[0], text)
+      if text[-1] != text[0] or len(text) < 2:
+         raise ValueError(f'unclosed quoted string. expected final character to be "{text[0]}" and length to be greater than 1 in "{text[0]}"')
       return text[1:-1]
     return text
 
@@ -1469,15 +1470,15 @@ def parse_string_list_members(text):
     while True:
       current = values[index].lstrip() # Cannot safely rstrip for cases like: "HERE-> ,"
       if not len(current):
-        exit_with_error('string array should not contain an empty value')
+        raise ValueError('empty value in string list')
       first = current[0]
       if not (first == "'" or first == '"'):
         result.append(current.rstrip())
       else:
         start = index
         while True: # Continue until closing quote found
           if index >= len(values):
-            exit_with_error("unclosed quoted string. expected final character to be '%s' in '%s'" % (first, values[start]))
+            raise ValueError(f"unclosed quoted string. expected final character to be '{first}' in '{values[start]}'")
           new = values[index].rstrip()
           if new and new[-1] == first:
             if start == index:
@@ -1498,7 +1499,7 @@ def parse_string_list(text):
     text = text.rstrip()
     if text and text[0] == '[':
       if text[-1] != ']':
-        exit_with_error('unclosed opened string list. expected final character to be "]" in "%s"' % (text))
+        raise ValueError('unterminated string list. expected final character to be "]"')
       text = text[1:-1]
     if text.strip() == "":
       return []

test/test_other.py

@@ -7663,19 +7663,22 @@ def test_dash_s_unclosed_quote(self):
     # Unclosed quote
     err = self.expect_fail([EMCC, test_file('hello_world.c'), '-s', "TEST_KEY='MISSING_QUOTE"])
     self.assertNotContained('AssertionError', err) # Do not mention that it is an assertion error
-    self.assertContained('unclosed opened quoted string. expected final character to be "\'"', err)
+    self.assertContained('error: error parsing "-s" setting', err)
+    self.assertContained('unclosed quoted string. expected final character to be "\'"', err)
 
   def test_dash_s_single_quote(self):
     # Only one quote
     err = self.expect_fail([EMCC, test_file('hello_world.c'), "-sTEST_KEY='"])
     self.assertNotContained('AssertionError', err) # Do not mention that it is an assertion error
-    self.assertContained('unclosed opened quoted string.', err)
+    self.assertContained('error: error parsing "-s" setting', err)
+    self.assertContained('unclosed quoted string.', err)
 
   def test_dash_s_unclosed_list(self):
     # Unclosed list
     err = self.expect_fail([EMCC, test_file('hello_world.cpp'), "-sTEST_KEY=[Value1, Value2"])
     self.assertNotContained('AssertionError', err) # Do not mention that it is an assertion error
-    self.assertContained('unclosed opened string list. expected final character to be "]"', err)
+    self.assertContained('error: error parsing "-s" setting', err)
+    self.assertContained('unterminated string list. expected final character to be "]"', err)
 
   def test_dash_s_valid_list(self):
     err = self.expect_fail([EMCC, test_file('hello_world.cpp'), "-sTEST_KEY=[Value1, \"Value2\"]"])