feat: a bit of manual parsing for better error

Author: AleksandrSl

src/main/gen/com/github/aleksandrsl/intellijbrowserslist/parser/BrowserslistParser.java

@@ -12,6 +12,8 @@
   elementTypeClass="com.github.aleksandrsl.intellijbrowserslist.psi.BrowserslistElementType"
   tokenTypeClass="com.github.aleksandrsl.intellijbrowserslist.psi.BrowserslistTokenType"
 
+  parserUtilClass="com.github.aleksandrsl.intellijbrowserslist.parser.BrowserslistParserUtil"
+
   tokens=[
     EOL="regexp:\R"
     LBRACKET="["
@@ -75,9 +77,10 @@ query ::=
     | defaultsQuery
 private query_recover ::= !(EOL|COMMENT|OR|AND|'[')
 
+
 private version ::= 'version' | 'versions'
 // TODO: Cover in custom stats like `cover 5% in browserslist-config-mycompany stats` should be supported?
-statsQuery ::= (COMPARE|'cover') PERCENT ('in' IDENTIFIER 'stats'?)? {pin=1}
+statsQuery ::= (COMPARE|'cover') PERCENT ('in' <<parseStats>>)? {pin=1}
 lastQuery ::= 'last' INTEGER TARGET? 'major'? version
 unreleasedQuery ::= 'unreleased' TARGET? version {pin=1}
 timeQuery ::= timeQueryLast_ | timeQuerySince_

src/main/grammar/Browserslist.bnf

@@ -0,0 +1,45 @@
+package com.github.aleksandrsl.intellijbrowserslist.parser
+
+import com.github.aleksandrsl.intellijbrowserslist.psi.BrowserslistTypes.IDENTIFIER
+import com.intellij.lang.PsiBuilder
+import com.intellij.lang.parser.GeneratedParserUtilBase
+import com.intellij.openapi.diagnostic.logger
+
+val countryCodeRegex = Regex("(alt-)?[a-z]{2}", option = RegexOption.IGNORE_CASE)
+
+private val LOG = logger<BrowserslistParserUtil>()
+
+object BrowserslistParserUtil : GeneratedParserUtilBase() {
+
+    /**
+     * Parses stats reference patterns:
+     * - "my stats"
+     * - "{IDENTIFIER} stats"
+     * - "(alt-)?{2 letter code}" (country codes like "us", "alt-us")
+     */
+    @JvmStatic
+    fun parseStats(builder: PsiBuilder, level: Int): Boolean {
+        if (!recursion_guard_(builder, level, "parseStats")) return false
+
+        var result = parseMyStats(builder)
+        if (!result) result = parseCountryCodeOrIdentifierStats(builder, level + 1)
+        return result
+    }
+
+    private fun parseMyStats(builder: PsiBuilder): Boolean {
+        return consumeToken(builder, "my", false) && consumeToken(builder, "stats", false)
+    }
+
+    private fun parseCountryCodeOrIdentifierStats(builder: PsiBuilder, level: Int): Boolean {
+        if (!recursion_guard_(builder, level, "parseStats_codeOrIdentifier")) return false
+        val text = builder.tokenText ?: return false
+
+        addVariant(builder, "xx or alt-xx (country code)")
+        if (countryCodeRegex.matchEntire(text) != null) {
+            builder.advanceLexer()
+            return true
+        } else {
+            return consumeToken(builder, IDENTIFIER) && consumeToken(builder, "stats", false)
+        }
+    }
+}