strict-boolean-expressions: Add 'allow-null-union', 'allow-undefined-union', 'allow-string', and 'allow-number' options #2033
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…union', 'allow-string', and 'allow-number' options
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Added an |
| @@ -178,6 +178,11 @@ export function isTypeFlagSet(type: ts.Type, flagToCheck: ts.TypeFlags): boolean | |||
| /* tslint:enable:no-bitwise */ | |||
| } | |||
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| /** Type predicate to test for a union type. */ | |||
| export function isUnionType(type: ts.Type): type is ts.UnionType { | |||
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shouldn't clutter utils with wrappers for isTypeFlagSet. I can imagine this getting out of control
| enum: [OPTION_ALLOW_NULL_UNION, OPTION_ALLOW_UNDEFINED_UNION, OPTION_ALLOW_STRING, OPTION_ALLOW_NUMBER], | ||
| }, | ||
| minLength: 0, | ||
| maxLength: 4, |
| declare function get<T>(): T; | ||
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| if (get<string | number>()) {} | ||
| ~~~~~~~~~~~~~~~~~~~~~~ [If statement condition may be falsy if it is 0. Expected a boolean, undefined-union, or string.] |
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This error is unclear. How about This type is not allowed in the 'if' condition because it could be a number. Allowed types are boolean, undefined-union, or string. You might have to modify it to make the string easier to generate
| if (get<string>()) {} | ||
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| if (get<boolean | string>()) {} | ||
| ~~~~~~~~~~~~~~~~~~~~~~~ [If statement condition mixes multiple kinds of falsy values. Expected a boolean or string.] |
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`This type is not allowed in the 'if' condition because it unions one or more disallowed truthy/falsy types. Allowed types are boolean or string
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Changed "one or more" to "more than one" since it allows having exactly one falsy type.
andy-hanson
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I like the idea of adding more options to 'strict-boolean-expressions'. Thank you for working on this. I haven't started yet, but I was planning to add a new option (ex. no-enum-boolean-coercion) to 'strict-boolean-expressions' because our team wants to enable the rule only for enum values first. It is risky because enum values start from 0 by default. On the other hand, we want to allow number-boolean-coercion if we're using enum as flags. (Ref: https://basarat.gitbooks.io/typescript/content/docs/enums.html#enums-as-flags ) Ref: #1555 Did you consider having options like:
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So, if you want to be as permissive as possible, just set all the flags. This will still be less permissive than TypeScript as Adding an |
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nice, thanks @andy-hanson! |
PR checklist
What changes did you make?
Added new options to
strict-boolean-expressionsto make it not quite as strict.TypeScript allows anything in an if-statement, so there's a lot of room in between that and requiring that everything be a boolean.
Is there anything you'd like reviewers to focus on?
This rule wouldn't allow you to use
string | numberas a condition even if bothallow-stringandallow-numberare on. I think that's fine.It will allow
number | undefinedifallow-undefinedis on, since that containsundefinedin the union. But it's probably dangerous if the user just wanted to test forundefined. Thoughts?