Add initial script to generate a TypeScript Enum

.editorconfig

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+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_style = space
+indent_size = 2
+insert_final_newline = true
+trim_trailing_whitespace = true

.travis.yml

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+language: node_js
+node_js:
+  - 8
+  - 10
+install:
+  - npm install
+script:
+  - npm build
+  - npm test

lib/index.ts

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+export { PostgresError } from './PostgresError';

lib/sync.ts

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+import { join } from 'path';
+import { writeFileSync } from 'fs';
+import lodashFlatten from 'lodash.flatten';
+import isomorphicFetch from 'isomorphic-fetch';
+
+const sourceUrl = (branch = 'master') =>
+  `https://github.com/postgres/postgres/raw/${branch}/src/backend/utils/errcodes.txt`;
+
+const getSourceText = (): Promise<string[]> =>
+  isomorphicFetch(sourceUrl())
+    .then(response => response.text())
+    .then(text => text.split('\n'));
+
+const stripCommentsAndEmptyLines = (lines: string[]) =>
+  lines.filter(line => line !== '' && line.charAt(0) !== '#');
+
+const sectionRegex = /^Section:\s(?<description>.*)$/;
+
+const groupBySections = (lines: string[]) => {
+  const sections: Record<string, { description: string, lines: string[] }> = {};
+  let currentSection = '';
+
+  lines.forEach(line => {
+    const matches = line.match(sectionRegex);
+
+    if (matches) {
+      currentSection = (matches as any).groups.description;
+      sections[currentSection] = {
+        description: currentSection,
+        lines: [],
+      };
+    } else {
+      sections[currentSection].lines.push(line);
+    }
+  });
+
+  return Object.values(sections);
+}
+
+const errorLineRegex =
+  /^(?<sqlstate>[A-Z0-9]*)\s*(?<severity>[EWS])\s*ERRCODE_(?<constant>[A-Z_]*)\s*(?<code>[a-z_]*)$/
+
+const parseErrorLine = (line: string) => {
+  const matches = line.match(errorLineRegex);
+
+  if (!matches) {
+    throw new Error(`Error parsing error line:\n\t"${line}"`);
+  }
+
+  const { sqlstate, severity, constant, code } = (matches as any).groups;
+
+  return { sqlstate, severity, constant, code  };
+};
+
+const parseSectionLines = (data: ReturnType<typeof groupBySections>) =>
+  data.map(({ lines, ...otherData }) => ({ errorCodes: lines.map(parseErrorLine), ...otherData }));
+
+const getEnum = async () => {
+  const errorSections =
+    await getSourceText()
+      .then(stripCommentsAndEmptyLines)
+      .then(groupBySections)
+      .then(parseSectionLines);
+
+  const enumEntries = errorSections.map(section =>
+    section.errorCodes.map(
+      errorCode => `  /** ${section.description}: [${errorCode.severity}] ${errorCode.code} */\n  ${errorCode.constant} = '${errorCode.sqlstate}',`,
+    ),
+  );
+
+  const allEntries = lodashFlatten(enumEntries);
+
+  return `export enum PostgresError {\n${
+    allEntries.join('\n')
+  }\n}\n`;
+}
+
+const writeEnum = (enumString: string) => {
+  writeFileSync(join(__dirname, '../lib/PostgresError.ts'), enumString);
+}
+
+getEnum().then(writeEnum);