ctags-lang-python¶
Random notes about tagging python source code with Universal Ctags
- Version
5.9.0
- Manual group
Universal Ctags
- Manual section
7
SYNOPSIS¶
DESCRIPTION¶
This man page gathers random notes about tagging python source code.
TAGGING import STATEMENTS¶
Summary¶
import X
name
kind
role
other noticeable fields
X
module
imported
N/A
import X as Y
name
kind
role
other noticeable fields
X
module
indirectlyImported
N/A
Y
namespace
definition
nameref:module:X
from X import *
name
kind
role
other noticeable fields
X
module
namespace
N/A
from X import Y
name
kind
role
other noticeable fields
X
module
namespace
N/A
Y
unknown
imported
scope:module:X
from X import Y as Z
name
kind
role
other noticeable fields
X
module
namespace
N/A
Y
unknown
indirectlyImported
scope:module:X
Z
unknown
definition
nameref:unknown:X
Examples¶
“input.py”
import X0
“output.tags” with “--options=NONE -o - --extras=+r --fields=+rzK input.py”
X0 input.py /^import X0$/;" kind:module roles:imported
A tag for an imported module has module kind with imported role. The
module is not defined here; it is defined in another file. So the tag for the
imported module is a reference tag; specify --extras=+r (or
--extras=+{reference}) option for tagging it. “roles:” field enabled with
--fields=+r is for recording the module is “imported” to the tag file.
“input.py”
import X1 as Y1
“output.tags” with “--options=NONE -o - --extras=+r --fields=+rzK --fields-Python=+{nameref} input.py”
X1 input.py /^import X1 as Y1$/;" kind:module roles:indirectlyImported
Y1 input.py /^import X1 as Y1$/;" kind:namespace roles:def nameref:module:X1
“Y1” introduces a new name and is defined here. So “Y1” is tagged as a
definition tag. “X1” is imported in a way that its name cannot be used
in this source file. For letting client tools know that the name cannot be used,
indirectlyImported role is assigned for “X1”. “Y1” is the name for
accessing objects defined in the module imported via “X1”. For recording this
relationship, nameref: field is attached to the tag of “Y1”. Instead of
module kind, namespace kind is assigned to “Y1” because “Y1” itself
isn’t a module.
“input.py”
from X2 import *
“output.tags” with “--options=NONE -o - --extras=+r --fields=+rzK input.py”
X2 input.py /^from X2 import *$/;" kind:module roles:namespace
The module is not defined here; it is defined in another file. So the tag for
the imported module is a reference tag. Unlike “X0” in “import X0”, “X2” may not
be used because the names defined in “X2” can be used in this source file. To represent
the difference namespace role is attached to “X2” instead of imported.
“input.py”
from X3 import Y3
“output.tags” with “--options=NONE -o - --extras=+r --fields=+rzKZ input.py”
X3 input.py /^from X3 import Y3$/;" kind:module roles:namespace
Y3 input.py /^from X3 import Y3$/;" kind:unknown scope:module:X3 roles:imported
“Y3” is a name for a language object defined in “X3” module. “scope:module:X3”
attached to “Y3” represents this relation between “Y3” and “X3”. ctags
assigns unknown kind to “Y3” because ctags cannot know whether “Y3” is a
class, a variable, or a function from the input file.
“input.py”
from X4 import Y4 as Z4
“output.tags” with “--options=NONE -o - --extras=+r --fields=+rzKZ input.py”
X4 input.py /^from X4 import Y4 as Z4$/;" kind:module roles:namespace
Y4 input.py /^from X4 import Y4 as Z4$/;" kind:unknown scope:module:X4 roles:indirectlyImported
Z4 input.py /^from X4 import Y4 as Z4$/;" kind:unknown roles:def nameref:unknown:Y4
“Y4” is similar to “Y3” of “from X3 import Y3” but the name cannot be used here.
indirectlyImported role assigned to “Y4” representing this. “Z4” is the name for
accessing the language object named in “Y4” in “X4” module. “nameref:unknown:Y4”
attached to “Z4” and “scope:module:X4” attached to “Y4” represent the relations.
LAMBDA EXPRESSION AND TYPE HINT¶
Summary¶
id = lambda var0: var0
name
kind
role
other noticeable fields
id
function
definition
signature:(var0)
id_t: Callable[[int], int] = lambda var1: var1
name
kind
role
other noticeable fields
id_t
variable
definition
typeref:typename:Callable[[int], int] nameref:function:anonFuncN
anonFuncN
function
definition
signature:(var1)
Examples¶
“input.py”
from typing import Callable
id = lambda var0: var0
id_t: Callable[[int], int] = lambda var1: var1
“output.tags” with “--options=NONE -o - --sort=no --fields=+KS --fields-Python=+{nameref} --extras=+{anonymous} input.py”
id input.py /^id = lambda var0: var0$/;" function signature:(var0)
id_t input.py /^id_t: Callable[[int], int] = lambda var1: var1$/;"\
variable typeref:typename:Callable[[int], int] nameref:function:anonFunc84011d2c0101
anonFunc84011d2c0101 input.py /^id_t: Callable[[int], int] = lambda var1: var1$/;"\
function signature:(var1)
If a variable (“id”) with no type hint is initialized with a lambda expression,
ctags assigns function kind for the tag of “id”.
If a variable (“id_t”) with a type hint is initialized with a lambda expression,
ctags assigns variable kind for the tag of “id_t” with typeref: and
nameref: fields. ctags fills typeref: field with the value of the type
hint. The way of filling nameref: is a bit complicated.
For the lambda expression used in initializing the type-hint’ed variable, ctags
creates anonymous extra tag (“anonFunc84011d2c0101”). ctags fills the
nameref: field of “id_t” with the name of anonymous extra tag:
“nameref:function:anonFunc84011d2c0101”.
You may think why ctags does so complicated, and why ctags doesn’t emit following tags output for the input:
id input.py /^id = \\$/;" function signature:(var0)
id_t input.py /^id_t: \\$/;" function typeref:typename:Callable[[int], int] signature:(var1)
There is a reason. The other languages of ctags obey the following rule: ctags fills
typeref: field for a tag of a callable object (like function) with the type
of its return value. If we consider “id_t” is a function, its typeref: field
should have “typename:int”. However, for filling typeref: with “typename:int”,
ctags has to analyze “Callable[[int], int]” deeper. We don’t want to do so.