Implement SQL Formatting Rules for Function Names

[xterao]

This update introduces formal formatting rules for handling function names in SQL statements.

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Implemented Features

• Defined elements to represent function names with a new element type: FUNCTION_NAME.
• Escape handling:
  When a function name is enclosed in escape characters (e.g., double quotes or backticks), ensure no extra spaces are inserted between the escape symbols and the function name.
• Case sensitivity:
  Unlike keywords, function names are not automatically uppercased during formatting.

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Token Registration by Database

• Registered some commonly used function names as tokens per database:

  • PostgreSQL
  • MySQL
  • Oracle

• Implemented token management classes per database dialect.

• The lexer determines whether a token is a function name via a helper class that references these token sets.

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Reference Documentation

• PostgreSQL:
  https://www.postgresql.jp/docs/9.4/functions.html
• MySQL:
  https://dev.mysql.com/doc/refman/8.0/ja/functions.html
• Oracle:
  https://docs.oracle.com/en/database/oracle/oracle-database/23/sqlrf/Functions.html

[Copilot]

Pull Request Overview

This PR implements formal SQL formatting rules to recognize and correctly format function names, especially when escaped, without altering their case.

• Introduce a new FUNCTION_NAME token type in lexer, grammar, and syntax highlighter.
• Add custom spacing rules to prevent extra spaces between function names and parentheses or escape characters.
• Register common SQL functions per dialect and aggregate them in a helper for token classification.

Reviewed Changes

Copilot reviewed 42 out of 43 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/test/testData/sql/formatter/SelectEscapeFunctionName.sql	Raw SQL fixture with extra spaces around escaped identifiers.
src/test/testData/sql/formatter/SelectEscapeFunctionName_format.sql	Expected formatted SQL ensuring no extra spaces around escapes.
src/test/kotlin/org/domaframework/doma/intellij/formatter/SqlFormatterTest.kt	Added testSelectEscapeFunctionNameFormatter to validate spacing.
src/main/kotlin/org/domaframework/doma/intellij/formatter/visitor/SqlFormatVisitor.kt	Updated to include SqlTypes.FUNCTION_NAME in formatting targets.
src/main/kotlin/org/domaframework/doma/intellij/formatter/builder/SqlFormattingModelBuilder.kt	Defined custom spacing rules for FUNCTION_NAME tokens.
src/main/java/org/domaframework/doma/intellij/tokens/SqlFunctionToken.java	Introduced default set of SQL functions for tokenization.
src/main/java/org/domaframework/doma/intellij/SqlTokenHelper.java	Aggregates function tokens across dialects for classification.
src/main/java/org/domaframework/doma/intellij/Sql.flex	Lexer updated to classify words as FUNCTION_NAME.
src/main/java/org/domaframework/doma/intellij/Sql.bnf	Grammar extended to recognize FUNCTION_NAME non-terminals.

Comments suppressed due to low confidence (3)

src/test/kotlin/org/domaframework/doma/intellij/formatter/SqlFormatterTest.kt:57

• Consider adding tests for non-escaped function names (e.g., SUM(col)) to verify spacing and case preservation rules.

    fun testSelectEscapeFunctionNameFormatter() {

src/main/java/org/domaframework/doma/intellij/Sql.flex:33

• [nitpick] Method isWindowFunction checks all function tokens, not just window functions; consider renaming to isFunctionToken or isFunctionName for clarity.

        private static boolean isWindowFunction(CharSequence word) {

src/main/kotlin/org/domaframework/doma/intellij/formatter/util/SqlBlockUtil.kt:282

• Returning a SqlKeywordBlock for a subsequent function group may misclassify parameters; consider returning a SqlFunctionParamBlock or appropriate function parameter block instead.

                        if (lastGroupBlock is SqlFunctionGroupBlock) {