Package Usage: go: github.com/nishanths/exhaustive
Package exhaustive defines an analyzer that checks exhaustiveness of switch
statements of enum-like constants in Go source code. The analyzer can
optionally also check exhaustiveness of keys in map literals whose key type
is enum-like.
The Go language spec does not have an explicit definition for enums. For
the purpose of this analyzer, and by convention, an enum type is any named
type that:
In the example below, Biome is an enum type. The three constants are its
enum members.
Enum member constants for an enum type must be declared in the same block as
the type. The constant values may be specified using iota, literal values, or
any valid means for declaring a Go constant. It is allowed for multiple enum
member constants for an enum type to have the same constant value.
A switch statement that switches on a value of an enum type is exhaustive if
all enum members are listed in the switch statement's cases. If multiple enum
members have the same constant value, it is sufficient for any one of these
same-valued members to be listed.
For an enum type defined in the same package as the switch statement, both
exported and unexported enum members must be listed to satisfy exhaustiveness.
For an enum type defined in an external package, it is sufficient that only
exported enum members are listed. Only constant identifiers (e.g. Tundra,
eco.Desert) listed in a switch statement's case clause can contribute towards
satisfying exhaustiveness; other expressions, such as literal values and
function calls, listed in case clauses do not contribute towards satisfying
exhaustiveness.
By default, the existence of a default case in a switch statement does not
unconditionally make a switch statement exhaustive. Use the
-default-signifies-exhaustive flag to adjust this behavior.
For a map literal whose key type is an enum type, a similar definition of
exhaustiveness applies. The map literal is considered exhaustive if all enum
members are be listed in its keys. Empty map literals are never checked for
exhaustiveness.
A switch statement that switches on a value whose type is a type parameter is
checked for exhaustiveness if and only if each type element in the type
constraint is an enum type and the type elements share the same underlying
BasicKind.
For example, the switch statement below will be checked because each type
element (i.e. M and N) in the type constraint is an enum type and the type
elements share the same underlying BasicKind, namely int8. To satisfy
exhaustiveness, the enum members collectively belonging to the enum types M
and N (i.e. A, B, and C) must be listed in the switch statement's cases.
The analyzer handles type aliases as shown in the example below. newpkg.M is
an enum type. oldpkg.M is an alias for newpkg.M. Note that oldpkg.M isn't
itself an enum type; oldpkg.M is simply an alias for the actual enum type
newpkg.M.
A switch statement that switches either on a value of type newpkg.M or of type
oldpkg.M (which, being an alias, is just an alternative spelling for newpkg.M)
is exhaustive if all of newpkg.M's enum members are listed in the switch
statement's cases. The following switch statement is exhaustive.
The analyzer guarantees that introducing a type alias (such as type M =
newpkg.M) will not result in new diagnostics if the set of enum member
constant values of the RHS type is a subset of the set of enum member constant
values of the LHS type.
Summary:
Descriptions:
To skip analysis of a switch statement or a map literal, associate it with a
comment that begins with "//exhaustive:ignore". For example:
To ignore specific constants in exhaustiveness checks, specify the
-ignore-enum-members flag:
To ignore specific types, specify the -ignore-enum-types flag:
45 versions
Latest release: over 1 year ago
1,391 dependent packages
View more package details: https://packages.ecosystem.code.gouv.fr/registries/proxy.golang.org/packages/github.com/nishanths/exhaustive