Make whitespace skipping explicit when tokenizing expressions

This prevents some invalid expressions from being parsed - for example, whitespace isn't valid in identifiers

src/main/java/kroppeb/stareval/parser/StringReader.java

@@ -3,7 +3,7 @@
 import kroppeb.stareval.exception.UnexpectedCharacterException;
 
 /**
- * A class to facilitate the reading of strings, will completely ignore all spaces.
+ * A class to facilitate the reading of strings.
  */
 public class StringReader {
 	/**
@@ -47,6 +47,9 @@ private void advanceOneCharacter() {
 		this.nextIndex++;
 	}
 
+	/**
+	 * Skips all whitespace characters until a non-whitespace character is encountered.
+	 */
 	public void skipWhitespace() {
 		while (this.nextIndex < this.string.length() && this.string.charAt(this.nextIndex) == ' ') {
 			this.nextIndex++;
@@ -73,7 +76,6 @@ public void skipOneCharacter() {
 	public char read() {
 		char current = this.peek();
 		this.skipOneCharacter();
-		this.skipWhitespace();
 		return current;
 	}
 
@@ -106,7 +108,6 @@ public boolean tryRead(char c) {
 		}
 
 		this.skipOneCharacter();
-		this.skipWhitespace();
 		return true;
 	}
 

src/main/java/kroppeb/stareval/parser/Tokenizer.java

@@ -20,12 +20,20 @@ static Expression parseInternal(StringReader input, ParserOptions options) throw
 		ParserOptions.TokenRules tokenRules = options.getTokenRules();
 
 		while (input.canRead()) {
+			input.skipWhitespace();
+
+			if (!input.canRead()) {
+				break;
+			}
+
 			char c = input.read();
 
 			if (tokenRules.isIdStart(c)) {
 				final String id = readWhile(input, tokenRules::isIdPart);
 				stack.visitId(id);
 			} else if (c == '.' && stack.canReadAccess()) {
+				input.skipWhitespace();
+
 				if (input.canRead()) {
 					char start = input.read();
 

src/test/resources/shouldBeAbleToBeParsed.csv

@@ -31,4 +31,7 @@ a * b / c % d
 a + b - c
 a == b && b != c || c < d || d >= e || e <= f && f > h
 a + b * c - d % r * f * f / f - u + u
-
+test.field
+test. field
+test .field
+test . field

src/test/resources/shouldNotBeAbleToBeParsed.csv

@@ -31,3 +31,4 @@ stone,
 ,5
 5,
 5+,
+spaces in identifiers are not valid