feat: expand scenarios covered by default arguments for environments (#…

…20)

index.js

@@ -1,7 +1,39 @@
 'use strict';
 
+function getMainArgs() {
+  // This function is a placeholder for proposed process.mainArgs.
+  // Work out where to slice process.argv for user supplied arguments.
+
+  // Electron is an interested example, with work-arounds implemented in
+  // Commander and Yargs. Hopefully Electron would support process.mainArgs
+  // itself and render this work-around moot.
+  //
+  // In a bundled Electron app, the user CLI args directly
+  // follow executable. (No special processing required for unbundled.)
+  // 1) process.versions.electron is either set by electron, or undefined
+  //    see https://github.com/electron/electron/blob/master/docs/api/process.md#processversionselectron-readonly
+  // 2) process.defaultApp is undefined in a bundled Electron app, and set
+  //    in an unbundled Electron app
+  //    see https://github.com/electron/electron/blob/master/docs/api/process.md#processversionselectron-readonly
+  // (Not included in tests as hopefully temporary example.)
+  /* c8 ignore next 3 */
+  if (process.versions && process.versions.electron && !process.defaultApp) {
+    return process.argv.slice(1);
+  }
+
+  // Check node options for scenarios where user CLI args follow executable.
+  const execArgv = process.execArgv;
+  if (execArgv.includes('-e') || execArgv.includes('--eval') ||
+      execArgv.includes('-p') || execArgv.includes('--print')) {
+    return process.argv.slice(1);
+  }
+
+  // Normally first two arguments are executable and script, then CLI arguments
+  return process.argv.slice(2);
+}
+
 const parseArgs = (
-  argv = process.argv.slice(require.main ? 2 : 1),
+  argv = getMainArgs(),
   options = {}
 ) => {
   if (typeof options !== 'object' || options === null) {

test/index.js

@@ -68,19 +68,108 @@ test('args are passed "withValue" and "multiples"', function (t) {
   t.end()
 })
 
+test('correct default args when use node -p', function(t) {
+  const holdArgv = process.argv;
+  process.argv = [process.argv0, '--foo'];
+  const holdExecArgv = process.execArgv;
+  process.execArgv = ['-p', '0'];
+  const result = parseArgs();
+
+  const expected = { flags: { foo: true },
+                     values: { foo: [undefined] },
+                     positionals: [] };
+  t.deepEqual(result, expected);
+
+  t.end();
+  process.argv = holdArgv;
+  process.execArgv = holdExecArgv;
+});
+
+test('correct default args when use node --print', function(t) {
+  const holdArgv = process.argv;
+  process.argv = [process.argv0, '--foo'];
+  const holdExecArgv = process.execArgv;
+  process.execArgv = ['--print', '0'];
+  const result = parseArgs();
+
+  const expected = { flags: { foo: true },
+                     values: { foo: [undefined] },
+                     positionals: [] };
+  t.deepEqual(result, expected);
+
+  t.end();
+  process.argv = holdArgv;
+  process.execArgv = holdExecArgv;
+});
+
+test('correct default args when use node -e', function(t) {
+  const holdArgv = process.argv;
+  process.argv = [process.argv0, '--foo'];
+  const holdExecArgv = process.execArgv;
+  process.execArgv = ['-e', '0'];
+  const result = parseArgs();
+
+  const expected = { flags: { foo: true },
+                     values: { foo: [undefined] },
+                     positionals: [] };
+  t.deepEqual(result, expected);
+
+  t.end();
+  process.argv = holdArgv;
+  process.execArgv = holdExecArgv;
+});
+
+test('correct default args when use node --eval', function(t) {
+  const holdArgv = process.argv;
+  process.argv = [process.argv0, '--foo'];
+  const holdExecArgv = process.execArgv;
+  process.execArgv = ['--eval', '0'];
+  const result = parseArgs();
+
+  const expected = { flags: { foo: true },
+                     values: { foo: [undefined] },
+                     positionals: [] };
+  t.deepEqual(result, expected);
+
+  t.end();
+  process.argv = holdArgv;
+  process.execArgv = holdExecArgv;
+});
+
+test('correct default args when normal arguments', function(t) {
+  const holdArgv = process.argv;
+  process.argv = [process.argv0, 'script.js', '--foo'];
+  const holdExecArgv = process.execArgv;
+  process.execArgv = [];
+  const result = parseArgs();
+
+  const expected = { flags: { foo: true },
+                     values: { foo: [undefined] },
+                     positionals: [] };
+  t.deepEqual(result, expected);
+
+  t.end();
+  process.argv = holdArgv;
+  process.execArgv = holdExecArgv;
+});
+
 test('excess leading dashes on options are retained', function(t) {
   // Enforce a design decision for an edge case.
   const passedArgs = ['---triple'];
   const passedOptions = { };
-  const expected = { flags: { '-triple': true}, values: { '-triple': [undefined]}, positionals: [] };
-  const args = parseArgs(passedArgs, passedOptions);
+  const expected = {
+    flags: { '-triple': true },
+    values: { '-triple': [undefined] },
+    positionals: []
+  };
+  const result = parseArgs(passedArgs, passedOptions);
 
-  t.deepEqual(args, expected, 'excess option dashes are retained');
+  t.deepEqual(result, expected, 'excess option dashes are retained');
 
   t.end();
 });
 
-//Test bad inputs
+// Test bad inputs
 
 test('boolean passed to "withValue" option', function (t) {
   const passedArgs = ['--so=wat']