warning is emitted for unused arguments/variables prefixed with underscore

[Rogach]

Describe the bug

A warning is emitted for unused arguments/variables, even though they are prefixed with an underscore.

Code or Screenshots

Here's an example:

def foo(_a):
    _b = 42
    return 3

Here, both _a and _b will have a warning on their lines, something like "_a" is not accessed.

Versions

pyright 1.1.407, 1.1.408 and latest git, running from Emacs with lsp-pyright.

Possible fix

The problem arises here:

pyright/packages/pyright-internal/src/analyzer/checker.ts

Lines 3862 to 3872 in 28ea84a

	if (nameNode) {
	this._fileInfo.diagnosticSink.addUnusedCodeWithTextRange(
	LocMessage.unaccessedSymbol().format({ name: nameNode.d.value }),
	nameNode,
	action
	);
	if (rule !== undefined && message && diagnosticLevel !== 'none') {
	this._evaluator.addDiagnostic(rule, message, nameNode);
	}
	}

Looks like the diagnosticLevel !== 'none' check should be moved to the "if" one level back, like this:

--- a/packages/pyright-internal/src/analyzer/checker.ts
+++ b/packages/pyright-internal/src/analyzer/checker.ts
@@ -3859,14 +3859,14 @@ export class Checker extends ParseTreeWalker {
         }

         const action = rule === DiagnosticRule.reportUnusedImport ? { action: Commands.unusedImport } : undefined;
-        if (nameNode) {
+        if (nameNode && diagnosticLevel !== 'none') {
             this._fileInfo.diagnosticSink.addUnusedCodeWithTextRange(
                 LocMessage.unaccessedSymbol().format({ name: nameNode.d.value }),
                 nameNode,
                 action
             );

-            if (rule !== undefined && message && diagnosticLevel !== 'none') {
+            if (rule !== undefined && message) {
                 this._evaluator.addDiagnostic(rule, message, nameNode);
             }
         }