Integration

import ts from "typescript";

function createPlugin(info: ts.server.PluginCreateInfo): ts.LanguageService {
  const ls = info.languageService;
  const prefix: string = info.config?.prefix ?? "[lint]";
  return {
    ...ls,
    getSemanticDiagnostics: function(fileName: string) {
      const prior = ls.getSemanticDiagnostics(fileName);
      const sf = ls.getProgram().getSourceFile(fileName);
      if (!sf) return prior;
      const extras: ts.Diagnostic[] = [];
      function visit(node: ts.Node) {
        if (ts.isVariableDeclaration(node) && !node.type) {
          extras.push({
            file: sf,
            start: node.getStart(sf),
            length: node.getWidth(sf),
            category: ts.DiagnosticCategory.Warning,
            code: 9001,
            messageText: prefix + " Missing type annotation",
          });
        }
        ts.forEachChild(node, visit);
      }
      visit(sf);
      return [...prior, ...extras];
    },
    getCodeFixesAtPosition: function(fileName: string, start: number, end: number, errorCodes: readonly number[], formatOptions: ts.FormatCodeSettings, preferences: ts.UserPreferences) {
      const prior = ls.getCodeFixesAtPosition(fileName, start, end, errorCodes, formatOptions, preferences);
      const sf = ls.getProgram().getSourceFile(fileName);
      if (!sf) return prior;
      const fixes: ts.CodeFixAction[] = [];
      function visit(node: ts.Node) {
        if (ts.isVariableDeclaration(node) && !node.type) {
          fixes.push({
            fixName: "add-any",
            description: "Add type annotation",
            changes: [{
              fileName,
              textChanges: [{ span: { start: node.name.getEnd(), length: 0 }, newText: ": any" }],
            }],
          });
        }
        ts.forEachChild(node, visit);
      }
      visit(sf);
      return [...prior, ...fixes];
    },
  };
}

const sf = ts.createSourceFile("app.ts", "let x = 1;", ts.ScriptTarget.Latest, true);
const fakeLs = {
  getSemanticDiagnostics: function() { return [] as ts.Diagnostic[]; },
  getCodeFixesAtPosition: function() { return [] as ts.CodeFixAction[]; },
  getProgram: function() { return { getSourceFile: function(n: string) { return n === "app.ts" ? sf : undefined; } } as unknown as ts.Program; },
} as unknown as ts.LanguageService;

const info = { languageService: fakeLs, config: { prefix: "[L]" } } as unknown as ts.server.PluginCreateInfo;
const plugin = createPlugin(info);
const diags = plugin.getSemanticDiagnostics("app.ts");
const fixes = plugin.getCodeFixesAtPosition("app.ts", 0, 1, [], {} as ts.FormatCodeSettings, {} as ts.UserPreferences);
console.log(diags.length + " " + fixes[0].fixName);