Debug Protocol: Allow exception conditions to be specified by the protocol

[richardstanton]

In Visual Studio, users can ignore first chance exceptions when they are raised in specific modules. This is useful when an external component raises a lot of exceptions that the user does not care about. This feature can be supported by the protocol by adding the concept of exception conditions. Although these conditions are currently either "Module == name" or "Module != name" this proposal lets the condition type be specified in case other condition types are added.

/** An ExceptionOptions assigns configuration options to a set of exceptions.*/
export interface ExceptionOptions {

    // ....

    /** A set of conditions used to determine whether the exception should result in a break.
        The debugger will break only if the exception matches all listed conditions.*/
    conditions?: ExceptionCondition[];
}

/** Condition to determine if the exception should be handled by the debugger.*/
export interface ExceptionCondition {
    /** Type of the condition.*/
    type: 'module';
    /** Operation to apply to the condition value.*/
    operator?: 'equals' | 'notEquals';
    /** Value of the condition.*/
    value: string;
}

/** Information about the capabilities of a debug adapter.*/
export interface Capabilities {

    // ....

    /** The debug adapter supports using exception conditions in exception options.*/
    supportsExceptionConditions?: boolean;
}

@weinand @andrewcrawley @gregg-miskelly

[gregg-miskelly]

LGTM

[weinand]

Since the DAP already has a notion of a breakpoint condition, I would like to align exception conditions to breakpoint conditions (and other similar constructs).

Neither for breakpoint conditions, nor for the eval request did we specify the concrete syntax of those conditions and/or expressions (since the syntax would be language specific).

Would it be possible to just use a string typed attribute condition in the ExceptionOptions?
A language agnostic debugger like VS Code would offer a text input box to specify the condition and the DA would return an error in case of a syntax error?

[andrewcrawley]

Breakpoint conditions and evaluations are language-specific, as you noted, so it makes sense to have a free-form experience. Exception conditions (at least in VS) are a bit different, though - the only exception condition VS supports is "Only break if the exception is/is not in this module", and it's exposed through a query-builder sort of UI:

We don't have any way to expose a free-form text field to users. We could potentially convert the conditions designed using the UI into a language-specific string, but that would require adapter authors to write a component on the VS side that would do the translation, which we've tried to avoid.

[weinand]

@richardstanton fyi:
With #137 we have added condition support for exceptions in a way that is aligned with conditional breakpoints. VS Code already supports the new DAP feature and it would be possible to have conditions like "moduleName == foo && moduleName == bar".