Find unused functions from the command line?

[lydell]

Sorry if this is a stupid question – I’ve been looking through the repos but haven’t found what I’m looking for.

Is it possible to run this project as a command line tool?

Specifically I would like to find unused functions via the command line.

[TheAngryByrd]

Is it possible to run this project as a command line tool?

Yes, but this a program that follows the LSP protocol. It's only usuable by clients that use the LSP APis.

Specifically I would like to find unused functions via the command line.

This would be better suited as an F# analyzer. You can see some examples of analyzers from Ionide and from G-Research

[lydell]

Thanks!

I managed to create a Hello World analyzer, but then writing an analyzer that correctly identifies unused functions turned out to be too difficult for me. I was hoping I could use what already exists in FsAutoComplete.

I asked on Discord too, and @baronfel made this cool script: https://gist.github.com/baronfel/df0781136177b805c37ac685f2f61f04

Meanwhile, I settled for a hacky script (I wrote it in Node.js since that executes quickly and I have it installed anyway):

// @ts-check

import fs from "node:fs";
import path from "node:path";

/**
 * @param dir {string}
 * @returns {void}
 */
function run(dir) {
  for (const item of fs.readdirSync(dir, { recursive: true })) {
    if (item.endsWith(".fs")) {
      checkFile(path.join(dir, item));
    }
  }
}

// https://github.com/fsharp/fslang-spec/blob/1890512002c43f832cbdd6524587c22563589403/spec/lexical-analysis.md#identifiers-and-keywords
const privateLetRegex =
  /^( *let +private +)([\p{Lu}\p{Ll}\p{Lt}\p{Lm}\p{Lo}\p{Nl}_][\p{Lu}\p{Ll}\p{Lt}\p{Lm}\p{Lo}\p{Nl}\p{Nd}\p{Pc}\p{Mn}\p{Mc}\p{Cf}'_]*)/gmu;

/**
 * @param filePath {string}
 * @returns {void}
 */
function checkFile(filePath) {
  const code = fs.readFileSync(filePath, "utf-8");
  for (const match of code.matchAll(privateLetRegex)) {
    const prefix = match[1];
    const name = match[2];
    const nameRegex = new RegExp(`\\b${name}\\b`, "g");
    // Find the first match (there must be at least one since we matched `let private NAME`).
    nameRegex.exec(code);
    // Find the next match. If there aren’t any, it’s unused.
    if (nameRegex.exec(code) === null) {
      const location = indexToLineAndColumn(match.index + prefix.length, code);
      console.log(
        `${filePath}:${location.line}:${location.column}: Unused private let: ${name}`,
      );
    }
  }
}

/**
 * @param index {number}
 * @param string {string}
 * @typedef {{ line: number, column: number }} FileLocation
 * @returns FileLocation
 */
function indexToLineAndColumn(index, string) {
  const slice = string.slice(0, index);
  const lines = slice.split("\n");
  const lastLine = lines[lines.length - 1];
  return {
    line: lines.length,
    column: lastLine.length + 1,
  };
}

run(import.meta.dirname);

The dream end game for me would be a CLI tool that would print all of FSAC’s diagnostics for an entire project. Then one could enforce (some of) them in CI, and stop being overwhelmed by accidentally left behind warnings in lots of files.