Add escape sequence support for string literals (\t, \n, \r, etc.)

[Copilot]

Description

AlaSQL now processes standard escape sequences in string literals. Previously, \t, \n, \r, and similar sequences were treated as literal characters rather than their control character equivalents.

This implementation focuses on essential escape sequences while maintaining backward compatibility with existing quote escaping mechanisms.

Changes

• Parser (src/alasqlparser.jison): Modified StringValue grammar rule to process escape sequences: \n, \t, \r, \\, \', \"
  • Uses specific regex /\\(n|t|r|\\|'|")/g to only match supported sequences
  • Removed support for \b, \f, \v to keep implementation conservative
  • Unsupported escape sequences are left as literal text (e.g., \x remains as \x)
• JSON compilation (src/58json.js): Fixed JSONtoJS to escape strings properly when generating JavaScript code, preventing syntax errors with embedded quotes
• Tests: Added test/test134-B.js with 8 test cases covering all supported escape sequences; updated test/test125.js to reflect new escape sequence behavior

Example

SELECT 'hello\tworld' AS result;
-- Returns: {result: 'hello	world'}

SELECT 'line1\nline2' AS result;  
-- Returns: {result: 'line1
-- line2'}

SELECT 'back\\slash' AS result;
-- Returns: {result: 'back\slash'}

SELECT * FROM CSV('data.csv', {quote:"\""});
-- Now correctly handles escaped quotes in parameters

Supported Escape Sequences

• \n - newline
• \t - tab
• \r - carriage return
• \\ - backslash
• \' - single quote
• \" - double quote

All other sequences (like \b, \f, \v, \x, etc.) are left as literal backslash + character.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Add \ t and similar characters to strings</issue_title>
<issue_description>Now AlaSQL does not support \t and other similar special characters.
</issue_description>

<agent_instructions>Name the test file test/test134-B.js</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@mathiasrw Have added this to feature requests so people can vote http://feathub.com/agershun/alasql/+27

• Fixes Add \ t and similar characters to strings #134

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[mathiasrw]

please remove \b \f \v support

[mathiasrw]

You dont know if the first \ is escaped beforehand. You will need to find pairs like \ (regex as \\) or not pair (what you got now \(.))

Please see if you can place regex outside of the executing function

[Copilot]

Fixed the regex to be more specific: /\\(n|t|r|\\|'|")/g instead of /\\(.)/g. This only matches the supported escape sequences and properly handles \\ without needing to worry about pairs. (57cfff3)

[mathiasrw]

Please check if this is being solved via #2335

[Copilot]

please remove \b \f \v support

Removed \b, \f, and \v support as requested. Now only supporting \n, \t, \r, \, ', and " escape sequences. (57cfff3)

[mathiasrw]

@copilot

What is we have a string of data that contains \n, will it then get converted?

[Copilot]

Yes, this is the correct behavior. When data contains actual newline characters (after SQL parsing converts \n to a newline), escapeq() converts them back to \n when generating JavaScript code. This ensures the generated JS code is syntactically valid.

Flow:

1. SQL 'hello\nworld' → Parser converts to actual newline → Stored in memory as hello<LF>world
2. When generating JS code → escapeq() converts back to \n → Generated code: "hello\nworld"
3. JS runtime executes → Results in newline character again

Without escapeq(), strings with newlines/quotes would produce invalid JavaScript syntax.