summaryrefslogtreecommitdiffhomepage
path: root/scripts/jinja2/debug.py
blob: 805866bd6f9b04dcde0c36a7e72739f5b3759dd0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
import platform
import sys
import typing as t
from types import CodeType
from types import TracebackType

from .exceptions import TemplateSyntaxError
from .utils import internal_code
from .utils import missing

if t.TYPE_CHECKING:
    from .runtime import Context


def rewrite_traceback_stack(source: t.Optional[str] = None) -> BaseException:
    """Rewrite the current exception to replace any tracebacks from
    within compiled template code with tracebacks that look like they
    came from the template source.

    This must be called within an ``except`` block.

    :param source: For ``TemplateSyntaxError``, the original source if
        known.
    :return: The original exception with the rewritten traceback.
    """
    _, exc_value, tb = sys.exc_info()
    exc_value = t.cast(BaseException, exc_value)
    tb = t.cast(TracebackType, tb)

    if isinstance(exc_value, TemplateSyntaxError) and not exc_value.translated:
        exc_value.translated = True
        exc_value.source = source
        # Remove the old traceback, otherwise the frames from the
        # compiler still show up.
        exc_value.with_traceback(None)
        # Outside of runtime, so the frame isn't executing template
        # code, but it still needs to point at the template.
        tb = fake_traceback(
            exc_value, None, exc_value.filename or "<unknown>", exc_value.lineno
        )
    else:
        # Skip the frame for the render function.
        tb = tb.tb_next

    stack = []

    # Build the stack of traceback object, replacing any in template
    # code with the source file and line information.
    while tb is not None:
        # Skip frames decorated with @internalcode. These are internal
        # calls that aren't useful in template debugging output.
        if tb.tb_frame.f_code in internal_code:
            tb = tb.tb_next
            continue

        template = tb.tb_frame.f_globals.get("__jinja_template__")

        if template is not None:
            lineno = template.get_corresponding_lineno(tb.tb_lineno)
            fake_tb = fake_traceback(exc_value, tb, template.filename, lineno)
            stack.append(fake_tb)
        else:
            stack.append(tb)

        tb = tb.tb_next

    tb_next = None

    # Assign tb_next in reverse to avoid circular references.
    for tb in reversed(stack):
        tb_next = tb_set_next(tb, tb_next)

    return exc_value.with_traceback(tb_next)


def fake_traceback(  # type: ignore
    exc_value: BaseException, tb: t.Optional[TracebackType], filename: str, lineno: int
) -> TracebackType:
    """Produce a new traceback object that looks like it came from the
    template source instead of the compiled code. The filename, line
    number, and location name will point to the template, and the local
    variables will be the current template context.

    :param exc_value: The original exception to be re-raised to create
        the new traceback.
    :param tb: The original traceback to get the local variables and
        code info from.
    :param filename: The template filename.
    :param lineno: The line number in the template source.
    """
    if tb is not None:
        # Replace the real locals with the context that would be
        # available at that point in the template.
        locals = get_template_locals(tb.tb_frame.f_locals)
        locals.pop("__jinja_exception__", None)
    else:
        locals = {}

    globals = {
        "__name__": filename,
        "__file__": filename,
        "__jinja_exception__": exc_value,
    }
    # Raise an exception at the correct line number.
    code: CodeType = compile(
        "\n" * (lineno - 1) + "raise __jinja_exception__", filename, "exec"
    )

    # Build a new code object that points to the template file and
    # replaces the location with a block name.
    location = "template"

    if tb is not None:
        function = tb.tb_frame.f_code.co_name

        if function == "root":
            location = "top-level template code"
        elif function.startswith("block_"):
            location = f"block {function[6:]!r}"

    if sys.version_info >= (3, 8):
        code = code.replace(co_name=location)
    else:
        code = CodeType(
            code.co_argcount,
            code.co_kwonlyargcount,
            code.co_nlocals,
            code.co_stacksize,
            code.co_flags,
            code.co_code,
            code.co_consts,
            code.co_names,
            code.co_varnames,
            code.co_filename,
            location,
            code.co_firstlineno,
            code.co_lnotab,
            code.co_freevars,
            code.co_cellvars,
        )

    # Execute the new code, which is guaranteed to raise, and return
    # the new traceback without this frame.
    try:
        exec(code, globals, locals)
    except BaseException:
        return sys.exc_info()[2].tb_next  # type: ignore


def get_template_locals(real_locals: t.Mapping[str, t.Any]) -> t.Dict[str, t.Any]:
    """Based on the runtime locals, get the context that would be
    available at that point in the template.
    """
    # Start with the current template context.
    ctx: "t.Optional[Context]" = real_locals.get("context")

    if ctx is not None:
        data: t.Dict[str, t.Any] = ctx.get_all().copy()
    else:
        data = {}

    # Might be in a derived context that only sets local variables
    # rather than pushing a context. Local variables follow the scheme
    # l_depth_name. Find the highest-depth local that has a value for
    # each name.
    local_overrides: t.Dict[str, t.Tuple[int, t.Any]] = {}

    for name, value in real_locals.items():
        if not name.startswith("l_") or value is missing:
            # Not a template variable, or no longer relevant.
            continue

        try:
            _, depth_str, name = name.split("_", 2)
            depth = int(depth_str)
        except ValueError:
            continue

        cur_depth = local_overrides.get(name, (-1,))[0]

        if cur_depth < depth:
            local_overrides[name] = (depth, value)

    # Modify the context with any derived context.
    for name, (_, value) in local_overrides.items():
        if value is missing:
            data.pop(name, None)
        else:
            data[name] = value

    return data


if sys.version_info >= (3, 7):
    # tb_next is directly assignable as of Python 3.7
    def tb_set_next(
        tb: TracebackType, tb_next: t.Optional[TracebackType]
    ) -> TracebackType:
        tb.tb_next = tb_next
        return tb


elif platform.python_implementation() == "PyPy":
    # PyPy might have special support, and won't work with ctypes.
    try:
        import tputil  # type: ignore
    except ImportError:
        # Without tproxy support, use the original traceback.
        def tb_set_next(
            tb: TracebackType, tb_next: t.Optional[TracebackType]
        ) -> TracebackType:
            return tb

    else:
        # With tproxy support, create a proxy around the traceback that
        # returns the new tb_next.
        def tb_set_next(
            tb: TracebackType, tb_next: t.Optional[TracebackType]
        ) -> TracebackType:
            def controller(op):  # type: ignore
                if op.opname == "__getattribute__" and op.args[0] == "tb_next":
                    return tb_next

                return op.delegate()

            return tputil.make_proxy(controller, obj=tb)  # type: ignore


else:
    # Use ctypes to assign tb_next at the C level since it's read-only
    # from Python.
    import ctypes

    class _CTraceback(ctypes.Structure):
        _fields_ = [
            # Extra PyObject slots when compiled with Py_TRACE_REFS.
            ("PyObject_HEAD", ctypes.c_byte * object().__sizeof__()),
            # Only care about tb_next as an object, not a traceback.
            ("tb_next", ctypes.py_object),
        ]

    def tb_set_next(
        tb: TracebackType, tb_next: t.Optional[TracebackType]
    ) -> TracebackType:
        c_tb = _CTraceback.from_address(id(tb))

        # Clear out the old tb_next.
        if tb.tb_next is not None:
            c_tb_next = ctypes.py_object(tb.tb_next)
            c_tb.tb_next = ctypes.py_object()
            ctypes.pythonapi.Py_DecRef(c_tb_next)

        # Assign the new tb_next.
        if tb_next is not None:
            c_tb_next = ctypes.py_object(tb_next)
            ctypes.pythonapi.Py_IncRef(c_tb_next)
            c_tb.tb_next = c_tb_next

        return tb