noble (7) ctags-universal-lang-python.7.gz
NAME
ctags-lang-python - Random notes about tagging python source code with Universal Ctags
SYNOPSIS
ctags ... --languages=+Python ...
ctags ... --language-force=Python ...
ctags ... --map-Python=+.py ...
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:Y │
└─────┴─────────┴────────────────────┴────────────────────────┘
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.
SEE ALSO
ctags(1), ctags-client-tools(7), ctags-lang-iPythonCell(7)