defmodule Phoenix.LiveView.Component do
@moduledoc """
The struct returned by components in .heex templates.
This component is never meant to be output directly
into the template. It should always be handled by
the diffing algorithm.
"""
defstruct [:id, :component, :assigns]
@type t :: %__MODULE__{
id: binary(),
component: module(),
assigns: map()
}
defimpl Phoenix.HTML.Safe do
def to_iodata(%{id: id, component: component}) do
raise ArgumentError, """
cannot convert component #{inspect(component)} with id #{inspect(id)} to HTML.
A component must always be returned directly as part of a LiveView template.
For example, this is not allowed:
<%= content_tag :div do %>
<.live_component module={SomeComponent} id="myid" />
<% end %>
That's because the component is inside `content_tag`. However, this works:
<div>
<.live_component module={SomeComponent} id="myid" />
</div>
Components are also allowed inside Elixir's special forms, such as
`if`, `for`, `case`, and friends.
<%= for item <- items do %>
<.live_component module={SomeComponent} id={item} />
<% end %>
However, using other module functions such as `Enum`, will not work:
<%= Enum.map(items, fn item -> %>
<.live_component module={SomeComponent} id={item} />
<% end %>
"""
end
end
end
defmodule Phoenix.LiveView.Comprehension do
@moduledoc """
The struct returned by for-comprehensions in .heex templates.
See a description about its fields and use cases
in `Phoenix.LiveView.Engine` docs.
"""
defstruct [:static, :dynamics, :fingerprint]
@type t :: %__MODULE__{
static: [String.t()],
dynamics: [
[
iodata()
| Phoenix.LiveView.Rendered.t()
| Phoenix.LiveView.Comprehension.t()
| Phoenix.LiveView.Component.t()
]
],
fingerprint: integer()
}
defimpl Phoenix.HTML.Safe do
def to_iodata(%Phoenix.LiveView.Comprehension{static: static, dynamics: dynamics}) do
for dynamic <- dynamics, do: to_iodata(static, dynamic)
end
defp to_iodata([static_head | static_tail], [%_{} = struct | dynamic_tail]) do
dynamic_head = Phoenix.HTML.Safe.to_iodata(struct)
[static_head, dynamic_head | to_iodata(static_tail, dynamic_tail)]
end
defp to_iodata([static_head | static_tail], [dynamic_head | dynamic_tail]) do
[static_head, dynamic_head | to_iodata(static_tail, dynamic_tail)]
end
defp to_iodata([static_head], []) do
[static_head]
end
end
end
defmodule Phoenix.LiveView.Rendered do
@moduledoc """
The struct returned by .heex templates.
See a description about its fields and use cases
in `Phoenix.LiveView.Engine` docs.
"""
defstruct [:static, :dynamic, :fingerprint, :root]
@type t :: %__MODULE__{
static: [String.t()],
dynamic:
(boolean() ->
[
nil
| iodata()
| Phoenix.LiveView.Rendered.t()
| Phoenix.LiveView.Comprehension.t()
| Phoenix.LiveView.Component.t()
]),
fingerprint: integer(),
root: nil | true | false
}
defimpl Phoenix.HTML.Safe do
def to_iodata(%Phoenix.LiveView.Rendered{static: static, dynamic: dynamic}) do
to_iodata(static, dynamic.(false), [])
end
def to_iodata(%_{} = struct) do
Phoenix.HTML.Safe.to_iodata(struct)
end
def to_iodata(nil) do
raise "cannot convert .heex/.leex template with change tracking to iodata"
end
def to_iodata(other) do
other
end
defp to_iodata([static_head | static_tail], [dynamic_head | dynamic_tail], acc) do
to_iodata(static_tail, dynamic_tail, [to_iodata(dynamic_head), static_head | acc])
end
defp to_iodata([static_head], [], acc) do
Enum.reverse([static_head | acc])
end
end
end
defmodule Phoenix.LiveView.Engine do
@moduledoc ~S"""
An `EEx` template engine that tracks changes.
This is often used by `Phoenix.LiveView.HTMLEngine` which also adds
HTML validation. In the documentation below, we will explain how it
works internally. For user-facing documentation, see `Phoenix.LiveView`.
## Phoenix.LiveView.Rendered
Whenever you render a live template, it returns a
`Phoenix.LiveView.Rendered` structure. This structure has
three fields: `:static`, `:dynamic` and `:fingerprint`.
The `:static` field is a list of literal strings. This
allows the Elixir compiler to optimize this list and avoid
allocating its strings on every render.
The `:dynamic` field contains a function that takes a boolean argument
(see "Tracking changes" below), and returns a list of dynamic content.
Each element in the list is either one of:
1. iodata - which is the dynamic content
2. nil - the dynamic content did not change
3. another `Phoenix.LiveView.Rendered` struct, see "Nesting and fingerprinting" below
4. a `Phoenix.LiveView.Comprehension` struct, see "Comprehensions" below
5. a `Phoenix.LiveView.Component` struct, see "Component" below
When you render a live template, you can convert the
rendered structure to iodata by alternating the static
and dynamic fields, always starting with a static entry
followed by a dynamic entry. The last entry will always
be static too. So the following structure:
%Phoenix.LiveView.Rendered{
static: ["foo", "bar", "baz"],
dynamic: fn track_changes? -> ["left", "right"] end
}
Results in the following content to be sent over the wire
as iodata:
["foo", "left", "bar", "right", "baz"]
This is also what calling `Phoenix.HTML.Safe.to_iodata/1`
with a `Phoenix.LiveView.Rendered` structure returns.
Of course, the benefit of live templates is exactly
that you do not need to send both static and dynamic
segments every time. So let's talk about tracking changes.
## Tracking changes
By default, a live template does not track changes.
Change tracking can be enabled by including a changed
map in the assigns with the key `__changed__` and passing
`true` to the dynamic parts. The map should contain
the name of any changed field as key and the boolean
true as value. If a field is not listed in `__changed__`,
then it is always considered unchanged.
If a field is unchanged and live believes a dynamic
expression no longer needs to be computed, its value
in the `dynamic` list will be `nil`. This information
can be leveraged to avoid sending data to the client.
## Nesting and fingerprinting
`Phoenix.LiveView` also tracks changes across live
templates. Therefore, if your view has this:
<%= render "form.html", assigns %>
Phoenix will be able to track what is static and dynamic
across templates, as well as what changed. A rendered
nested `live` template will appear in the `dynamic`
list as another `Phoenix.LiveView.Rendered` structure,
which must be handled recursively.
However, because the rendering of live templates can
be dynamic in itself, it is important to distinguish
which live template was rendered. For example,
imagine this code:
<%= if something?, do: render("one.html", assigns), else: render("other.html", assigns) %>
To solve this, all `Phoenix.LiveView.Rendered` structs
also contain a fingerprint field that uniquely identifies
it. If the fingerprints are equal, you have the same
template, and therefore it is possible to only transmit
its changes.
## Comprehensions
Another optimization done by live templates is to
track comprehensions. If your code has this:
<%= for point <- @points do %>
x: <%= point.x %>
y: <%= point.y %>
<% end %>
Instead of rendering all points with both static and
dynamic parts, it returns a `Phoenix.LiveView.Comprehension`
struct with the static parts, that are shared across all
points, and a list of dynamics to be interpolated inside
the static parts. If `@points` is a list with `%{x: 1, y: 2}`
and `%{x: 3, y: 4}`, the above expression would return:
%Phoenix.LiveView.Comprehension{
static: ["\n x: ", "\n y: ", "\n"],
dynamics: [
["1", "2"],
["3", "4"]
]
}
This allows live templates to drastically optimize
the data sent by comprehensions, as the static parts
are emitted only once, regardless of the number of items.
The list of dynamics is always a list of iodatas or components,
as we don't perform change tracking inside the comprehensions
themselves. Similarly, comprehensions do not have fingerprints
because they are only optimized at the root, so conditional
evaluation, as the one seen in rendering, is not possible.
The only possible outcome for a dynamic field that returns a
comprehension is `nil`.
## Components
Live also supports stateful components defined with
`Phoenix.LiveComponent`. Since they are stateful, they are always
handled lazily by the diff algorithm.
"""
@behaviour Phoenix.Template.Engine
# TODO: Use @impl true instead of @doc false when we require Elixir v1.12
@doc false
def compile(path, _name) do
trim = Application.get_env(:phoenix, :trim_on_html_eex_engine, true)
EEx.compile_file(path, engine: __MODULE__, line: 1, trim: trim)
end
@behaviour EEx.Engine
@assigns_var Macro.var(:assigns, nil)
@doc false
def init(_opts) do
# Phoenix.LiveView.HTMLEngine calls this engine in a non-linear order
# to evaluate slots, which can lead to varible conflicts. Therefore we
# use a counter to ensure all variable names are unique.
%{
static: [],
dynamic: [],
counter: :counters.new(1, [])
}
end
@doc false
def handle_begin(state) do
%{state | static: [], dynamic: []}
end
@doc false
def handle_end(state) do
%{static: static, dynamic: dynamic} = state
safe = {:safe, Enum.reverse(static)}
{:__block__, [live_rendered: true], Enum.reverse([safe | dynamic])}
end
@doc false
def handle_body(state, opts \\ []) do
{:ok, rendered} = to_rendered_struct(handle_end(state), {:untainted, %{}}, %{}, opts)
quote do
require Phoenix.LiveView.Engine
unquote(rendered)
end
end
@doc false
def handle_text(state, text) do
handle_text(state, [], text)
end
@doc false
def handle_text(state, _meta, text) do
%{static: static} = state
%{state | static: [text | static]}
end
@doc false
def handle_expr(state, "=", ast) do
%{static: static, dynamic: dynamic, counter: counter} = state
i = :counters.get(counter, 1)
var = Macro.var(:"v#{i}", __MODULE__)
ast = quote do: unquote(var) = unquote(__MODULE__).to_safe(unquote(ast))
:counters.add(counter, 1, 1)
%{state | dynamic: [ast | dynamic], static: [var | static]}
end
def handle_expr(state, "", ast) do
%{dynamic: dynamic} = state
%{state | dynamic: [ast | dynamic]}
end
def handle_expr(state, marker, ast) do
EEx.Engine.handle_expr(state, marker, ast)
end
## Entry point for rendered structs
defp to_rendered_struct(expr, vars, assigns, opts) do
with {:__block__, [live_rendered: true], entries} <- expr,
{dynamic, [{:safe, static}]} <- Enum.split(entries, -1) do
{block, static, dynamic, fingerprint} =
analyze_static_and_dynamic(static, dynamic, vars, assigns)
changed =
quote generated: true do
case unquote(@assigns_var) do
%{__changed__: changed} when track_changes? -> changed
_ -> nil
end
end
{:ok,
quote do
dynamic = fn track_changes? ->
changed = unquote(changed)
unquote({:__block__, [], block})
unquote(dynamic)
end
%Phoenix.LiveView.Rendered{
static: unquote(static),
dynamic: dynamic,
fingerprint: unquote(fingerprint),
root: unquote(opts[:root])
}
end}
else
_ -> :error
end
end
defmacrop to_safe_match(var, ast) do
quote do
{:=, [],
[
{_, _, __MODULE__} = unquote(var),
{{:., _, [__MODULE__, :to_safe]}, _, [unquote(ast)]}
]}
end
end
defp analyze_static_and_dynamic(static, dynamic, initial_vars, assigns) do
{block, _} =
Enum.map_reduce(dynamic, initial_vars, fn
to_safe_match(var, ast), vars ->
vars = set_vars(initial_vars, vars)
{ast, keys, vars} = analyze_and_return_tainted_keys(ast, vars, assigns)
live_struct = to_live_struct(ast, vars, assigns)
{to_conditional_var(keys, var, live_struct), vars}
ast, vars ->
vars = set_vars(initial_vars, vars)
{ast, vars, _} = analyze(ast, vars, assigns)
{ast, vars}
end)
{static, dynamic} = bins_and_vars(static)
{block, static, dynamic, fingerprint(block, static)}
end
## Optimize possible expressions into live structs (rendered / comprehensions)
defp to_live_struct({:for, _, [_ | _]} = expr, vars, _assigns) do
with {:for, meta, [_ | _] = args} <- expr,
{filters, [[do: {:__block__, _, block}]]} <- Enum.split(args, -1),
{dynamic, [{:safe, static}]} <- Enum.split(block, -1) do
{block, static, dynamic, fingerprint} =
analyze_static_and_dynamic(static, dynamic, taint_vars(vars), %{})
for = {:for, meta, filters ++ [[do: {:__block__, [], block ++ [dynamic]}]]}
quote do
%Phoenix.LiveView.Comprehension{
static: unquote(static),
dynamics: unquote(for),
fingerprint: unquote(fingerprint)
}
end
else
_ -> to_safe(expr, true)
end
end
defp to_live_struct({left, meta, [_ | _] = args}, vars, assigns) do
call = extract_call(left)
args =
if classify_taint(call, args) in [:live, :render] do
{args, [opts]} = Enum.split(args, -1)
# The reason we can safely ignore assigns here is because
# each branch in the live/render constructs are their own
# rendered struct and, if the rendered has a new fingerpint,
# then change tracking is fully disabled.
#
# For example, take this code:
#
# <%= if @foo do %>
# <%= @bar %>
# <% else %>
# <%= @baz %>
# <% end %>
#
# In theory, @bar and @baz should be recomputed whenever
# @foo changes, because changing @foo may require a value
# that was not available on the page to show. However,
# given the branches have different fingerprints, the
# diff mechanism takes care of forcing all assigns to
# be rendered without us needing to handle it here.
#
# Similarly, when expanding the blocks, we can remove all
# untainting, as the parent untainting is already causing
# the block to be rendered and then we can proceed with
# its own tainting.
{args, vars, _} = analyze_list(args, vars, assigns, [])
opts =
for {key, value} <- opts do
{key, maybe_block_to_rendered(value, vars)}
end
args ++ [opts]
else
args
end
args =
case {call, args} do
# If we have a component, we provide change tracking to individual keys.
{:component, [fun, expr]} -> [fun, to_component_tracking(fun, expr, [], vars)]
{_, _} -> args
end
to_safe({left, meta, args}, true)
end
defp to_live_struct(expr, _vars, _assigns) do
to_safe(expr, true)
end
defp extract_call({:., _, [{:__aliases__, _, [:Phoenix, :LiveView, :Helpers]}, func]}),
do: func
defp extract_call(call),
do: call
defp maybe_block_to_rendered([{:->, _, _} | _] = blocks, vars) do
for {:->, meta, [args, block]} <- blocks do
{args, vars, assigns} = analyze_list(args, vars, %{}, [])
case to_rendered_struct(block, untaint_vars(vars), assigns, []) do
{:ok, rendered} -> {:->, meta, [args, rendered]}
:error -> {:->, meta, [args, block]}
end
end
end
defp maybe_block_to_rendered(block, vars) do
case to_rendered_struct(block, untaint_vars(vars), %{}, []) do
{:ok, rendered} -> rendered
:error -> block
end
end
defp to_conditional_var(:all, var, live_struct) do
quote do: unquote(var) = unquote(live_struct)
end
defp to_conditional_var(keys, var, live_struct) when keys == %{} do
quote do
unquote(var) =
case changed do
%{} -> nil
_ -> unquote(live_struct)
end
end
end
defp to_conditional_var(keys, var, live_struct) do
quote do
unquote(var) =
case unquote(changed_assigns(keys)) do
true -> unquote(live_struct)
false -> nil
end
end
end
defp changed_assigns(assigns) do
checks =
for {key, _} <- assigns, not nested_and_parent_is_checked?(key, assigns) do
case key do
[assign] ->
quote do
unquote(__MODULE__).changed_assign?(changed, unquote(assign))
end
[assign | tail] ->
quote do
unquote(__MODULE__).nested_changed_assign?(
unquote(@assigns_var),
changed,
unquote(assign),
unquote(tail)
)
end
end
end
Enum.reduce(checks, &{:or, [], [&1, &2]})
end
# If we are accessing @foo.bar.baz but in the same place we also pass
# @foo.bar or @foo, we don't need to check for @foo.bar.baz.
# If there is no nesting, then we are not nesting.
defp nested_and_parent_is_checked?([_], _assigns),
do: false
# Otherwise, we convert @foo.bar.baz into [:baz, :bar, :foo], discard :baz,
# and then check if [:foo, :bar] and then [:foo] is in it.
defp nested_and_parent_is_checked?(keys, assigns),
do: parent_is_checked?(tl(Enum.reverse(keys)), assigns)
defp parent_is_checked?([], _assigns),
do: false
defp parent_is_checked?(rest, assigns),
do: Map.has_key?(assigns, Enum.reverse(rest)) or parent_is_checked?(tl(rest), assigns)
## Component keys change tracking
defp to_component_tracking(fun, expr, extra, vars) do
# Separate static and dynamic parts
{static, dynamic} =
case expr do
{{:., _, [{:__aliases__, _, [:Map]}, :merge]}, _, [dynamic, {:%{}, _, static}]} ->
{static, dynamic}
{:%{}, _, static} ->
{static, %{}}
static ->
{static, %{}}
end
# And now validate the static bits. If they are not valid,
# treat the whole thing as dynamic.
{static, dynamic} =
if Keyword.keyword?(static) do
{static, dynamic}
else
{[], expr}
end
static_extra = extra ++ static
static_changed =
if static_extra != [] do
keys =
for {key, value} <- static_extra,
# We pass empty assigns because if this code is rendered,
# it means that upstream assigns were change tracked.
{_, keys, _} = analyze_and_return_tainted_keys(value, vars, %{}),
# If keys are empty, it is never changed.
keys != %{},
do: {key, to_component_keys(keys)}
quote do
unquote(__MODULE__).to_component_static(unquote(keys), unquote(@assigns_var), changed)
end
else
Macro.escape(%{})
end
static = slots_to_rendered(static, vars)
cond do
# We can't infer anything, so return the expression as is.
static_extra == [] and dynamic == %{} ->
expr
# Live components do not need to compute the changed because they track their own changed.
match?({:&, _, [{:/, _, [{:live_component, _, _}, 1]}]}, fun) ->
if dynamic == %{} do
quote do: %{unquote_splicing(static)}
else
quote do: Map.merge(unquote(dynamic), %{unquote_splicing(static)})
end
# We were actually able to find some static bits, but no dynamic.
# Embed the static parts alongside the computed changed.
dynamic == %{} ->
quote do
%{unquote_splicing([__changed__: static_changed] ++ static)}
end
# Merge both static and dynamic.
true ->
{_, keys, _} = analyze_and_return_tainted_keys(dynamic, vars, %{})
quote do
unquote(__MODULE__).to_component_dynamic(
%{unquote_splicing(static)},
unquote(dynamic),
unquote(static_changed),
unquote(to_component_keys(keys)),
unquote(@assigns_var),
changed
)
end
end
end
defp to_component_keys(:all), do: :all
defp to_component_keys(map), do: Map.keys(map)
@doc false
def to_component_static(_keys, _assigns, nil) do
nil
end
def to_component_static(keys, assigns, changed) do
for {assign, entries} <- keys,
changed = component_changed(entries, assigns, changed),
into: %{},
do: {assign, changed}
end
@doc false
def to_component_dynamic(static, dynamic, _static_changed, _keys, _assigns, nil) do
merge_dynamic_static_changed(dynamic, static, nil)
end
def to_component_dynamic(static, dynamic, static_changed, keys, assigns, changed) do
component_changed =
if component_changed(keys, assigns, changed) do
Enum.reduce(dynamic, static_changed, fn {k, _}, acc -> Map.put(acc, k, true) end)
else
static_changed
end
merge_dynamic_static_changed(dynamic, static, component_changed)
end
defp merge_dynamic_static_changed(dynamic, static, changed) do
dynamic |> Map.merge(static) |> Map.put(:__changed__, changed)
end
defp component_changed(:all, _assigns, _changed), do: true
defp component_changed([path], assigns, changed) do
case path do
[key] -> changed_assign(changed, key)
[key | tail] -> nested_changed_assign(assigns, changed, key, tail)
end
end
defp component_changed(entries, assigns, changed) do
Enum.any?(entries, fn
[key] -> changed_assign?(changed, key)
[key | tail] -> nested_changed_assign?(assigns, changed, key, tail)
end)
end
defp slots_to_rendered(static, vars) do
Macro.postwalk(static, fn
{call, meta, [name, [do: block]]} = node ->
if extract_call(call) == :inner_block do
{call, meta, [name, [do: maybe_block_to_rendered(block, vars)]]}
else
node
end
node ->
node
end)
end
## Extracts binaries and variable from iodata
defp bins_and_vars(acc),
do: bins_and_vars(acc, [], [])
defp bins_and_vars([bin1, bin2 | acc], bins, vars) when is_binary(bin1) and is_binary(bin2),
do: bins_and_vars([bin1 <> bin2 | acc], bins, vars)
defp bins_and_vars([bin, var | acc], bins, vars) when is_binary(bin) and is_tuple(var),
do: bins_and_vars(acc, [bin | bins], [var | vars])
defp bins_and_vars([var | acc], bins, vars) when is_tuple(var),
do: bins_and_vars(acc, ["" | bins], [var | vars])
defp bins_and_vars([bin], bins, vars) when is_binary(bin),
do: {Enum.reverse([bin | bins]), Enum.reverse(vars)}
defp bins_and_vars([], bins, vars),
do: {Enum.reverse(["" | bins]), Enum.reverse(vars)}
## Assigns tracking
# Here we compute if an expression should be always computed,
# never computed, or some times computed based on assigns.
#
# If any assign is used, we store it in the assigns and use it to compute
# if it should be changed or not.
#
# However, operations that change the lexical scope, such as imports and
# defining variables, taint the analysis. Because variables can be set at
# any moment in Elixir, via macros, without appearing on the left side of
# `=` or in a clause, whenever we see a variable, we consider it as tainted,
# regardless of its position.
#
# The tainting that happens from lexical scope is called weak-tainting,
# because it is disabled under certain special forms. There is also
# strong-tainting, which are always computed. Strong-tainting only happens
# if the `assigns` variable is used.
defp analyze_and_return_tainted_keys(ast, vars, assigns) do
{ast, vars, assigns} = analyze(ast, vars, assigns)
{tainted_assigns?, assigns} = Map.pop(assigns, __MODULE__, false)
keys = if match?({:tainted, _}, vars) or tainted_assigns?, do: :all, else: assigns
{ast, keys, vars}
end
# Nested assign
defp analyze_assign({{:., dot_meta, [Access, :get]}, meta, [left, right]}, vars, assigns, nest) do
{args, vars, assigns} =
if Macro.quoted_literal?(right) do
{left, vars, assigns} = analyze_assign(left, vars, assigns, [{:access, right} | nest])
{[left, right], vars, assigns}
else
{left, vars, assigns} = analyze(left, vars, assigns)
{right, vars, assigns} = analyze(right, vars, assigns)
{[left, right], vars, assigns}
end
{{{:., dot_meta, [Access, :get]}, meta, args}, vars, assigns}
end
defp analyze_assign({{:., dot_meta, [left, right]}, meta, []}, vars, assigns, nest) do
{left, vars, assigns} = analyze_assign(left, vars, assigns, [{:struct, right} | nest])
{{{:., dot_meta, [left, right]}, meta, []}, vars, assigns}
end
# Non-expanded assign
defp analyze_assign({:@, meta, [{name, _, context}]}, vars, assigns, nest)
when is_atom(name) and is_atom(context) do
expr =
quote line: meta[:line] || 0 do
unquote(__MODULE__).fetch_assign!(unquote(@assigns_var), unquote(name))
end
{expr, vars, Map.put(assigns, [name | nest], true)}
end
# Expanded assign access. The non-expanded form is handled on root,
# then all further traversals happen on the expanded form
defp analyze_assign(
{{:., _, [__MODULE__, :fetch_assign!]}, _, [{:assigns, _, nil}, name]} = expr,
vars,
assigns,
nest
)
when is_atom(name) do
{expr, vars, Map.put(assigns, [name | nest], true)}
end
defp analyze_assign(expr, vars, assigns, _nest) do
analyze(expr, vars, assigns)
end
# Delegates to analyze assign
defp analyze({{:., _, [Access, :get]}, _, [_, _]} = expr, vars, assigns) do
analyze_assign(expr, vars, assigns, [])
end
defp analyze({{:., _, [_, _]}, _, []} = expr, vars, assigns) do
analyze_assign(expr, vars, assigns, [])
end
defp analyze({:@, _, [{name, _, context}]} = expr, vars, assigns)
when is_atom(name) and is_atom(context) do
analyze_assign(expr, vars, assigns, [])
end
defp analyze(
{{:., _, [__MODULE__, :fetch_assign!]}, _, [{:assigns, _, nil}, name]} = expr,
vars,
assigns
)
when is_atom(name) do
analyze_assign(expr, vars, assigns, [])
end
# Assigns is a strong-taint
defp analyze({:assigns, _, nil} = expr, vars, assigns) do
{expr, vars, taint_assigns(assigns)}
end
# Our own vars are ignored. They appear from nested do/end in EEx templates.
defp analyze({_, _, __MODULE__} = expr, vars, assigns) do
{expr, vars, assigns}
end
# Ignore underscore
defp analyze({:_, _, context} = expr, vars, assigns) when is_atom(context) do
{expr, vars, assigns}
end
# Also skip special variables
defp analyze({name, _, context} = expr, vars, assigns)
when name in [:__MODULE__, :__ENV__, :__STACKTRACE__, :__DIR__] and is_atom(context) do
{expr, vars, assigns}
end
# Vars always taint unless we are in restricted mode.
defp analyze({name, _, context} = expr, {:restricted, map}, assigns)
when is_atom(name) and is_atom(context) do
if Map.has_key?(map, {name, context}) do
{expr, {:tainted, map}, assigns}
else
{expr, {:restricted, map}, assigns}
end
end
defp analyze({name, _, context} = expr, {_, map}, assigns)
when is_atom(name) and is_atom(context) do
{expr, {:tainted, Map.put(map, {name, context}, true)}, assigns}
end
# Ignore binary modifiers
defp analyze({:"::", meta, [left, right]}, vars, assigns) do
{left, vars, assigns} = analyze(left, vars, assigns)
{{:"::", meta, [left, right]}, vars, assigns}
end
# Classify calls
defp analyze({left, meta, args} = expr, vars, assigns) do
call = extract_call(left)
case classify_taint(call, args) do
:always ->
case vars do
{:restricted, _} -> {expr, vars, assigns}
{_, map} -> {expr, {:tainted, map}, assigns}
end
:render ->
{args, [opts]} = Enum.split(args, -1)
{args, vars, assigns} = analyze_list(args, vars, assigns, [])
{opts, vars, assigns} = analyze_with_restricted_vars(opts, vars, assigns)
{{left, meta, args ++ [opts]}, vars, assigns}
:none ->
{left, vars, assigns} = analyze(left, vars, assigns)
{args, vars, assigns} = analyze_list(args, vars, assigns, [])
{{left, meta, args}, vars, assigns}
# :never or :live
_ ->
{args, vars, assigns} = analyze_with_restricted_vars(args, vars, assigns)
{{left, meta, args}, vars, assigns}
end
end
defp analyze({left, right}, vars, assigns) do
{left, vars, assigns} = analyze(left, vars, assigns)
{right, vars, assigns} = analyze(right, vars, assigns)
{{left, right}, vars, assigns}
end
defp analyze([_ | _] = list, vars, assigns) do
analyze_list(list, vars, assigns, [])
end
defp analyze(other, vars, assigns) do
{other, vars, assigns}
end
defp analyze_list([head | tail], vars, assigns, acc) do
{head, vars, assigns} = analyze(head, vars, assigns)
analyze_list(tail, vars, assigns, [head | acc])
end
defp analyze_list([], vars, assigns, acc) do
{Enum.reverse(acc), vars, assigns}
end
# vars is one of:
#
# * {:tainted, map}
# * {:restricted, map}
# * {:untainted, map}
#
# Seeing a variable at any moment taints it unless we are inside a
# scope. For example, in case/cond/with/fn/try, the variable is only
# tainted if it came from outside of the case/cond/with/fn/try.
# So for those constructs we set the mode to restricted and stop
# collecting vars.
defp analyze_with_restricted_vars(ast, {kind, map}, assigns) do
{ast, {new_kind, _}, assigns} =
analyze(ast, {unless_tainted(kind, :restricted), map}, assigns)
{ast, {unless_tainted(new_kind, kind), map}, assigns}
end
defp set_vars({kind, _}, {_, map}), do: {kind, map}
defp taint_vars({_, map}), do: {:tainted, map}
defp untaint_vars({_, map}), do: {:untainted, map}
defp unless_tainted(:tainted, _), do: :tainted
defp unless_tainted(_, kind), do: kind
defp taint_assigns(assigns), do: Map.put(assigns, __MODULE__, true)
## Callbacks
defp fingerprint(block, static) do
<<fingerprint::8*16>> =
[block | static]
|> :erlang.term_to_binary()
|> :erlang.md5()
fingerprint
end
@doc false
defmacro to_safe(ast) do
to_safe(ast, false)
end
defp to_safe(ast, bool) do
to_safe(ast, line_from_expr(ast), bool)
end
defp line_from_expr({_, meta, _}) when is_list(meta), do: Keyword.get(meta, :line, 0)
defp line_from_expr(_), do: 0
defp to_safe(literal, _line, _extra_clauses?)
when is_binary(literal) or is_atom(literal) or is_number(literal) do
literal
|> Phoenix.HTML.Safe.to_iodata()
|> IO.iodata_to_binary()
end
defp to_safe(literal, line, _extra_clauses?) when is_list(literal) do
quote line: line, do: Phoenix.HTML.Safe.List.to_iodata(unquote(literal))
end
# Calls to attributes escape is always safe
defp to_safe(
{{:., _, [{:__aliases__, _, [:Phoenix, :HTML]}, :attributes_escape]}, _, [_]} =
safe,
line,
_extra_clauses?
) do
quote line: line do
elem(unquote(safe), 1)
end
end
defp to_safe(expr, line, false) do
quote line: line, do: unquote(__MODULE__).safe_to_iodata(unquote(expr))
end
defp to_safe(expr, line, true) do
quote line: line, do: unquote(__MODULE__).live_to_iodata(unquote(expr))
end
@doc false
def safe_to_iodata(expr) do
case expr do
{:safe, data} -> data
bin when is_binary(bin) -> Plug.HTML.html_escape_to_iodata(bin)
other -> Phoenix.HTML.Safe.to_iodata(other)
end
end
@doc false
def live_to_iodata(expr) do
case expr do
{:safe, data} -> data
%{__struct__: Phoenix.LiveView.Rendered} = other -> other
%{__struct__: Phoenix.LiveView.Component} = other -> other
%{__struct__: Phoenix.LiveView.Comprehension} = other -> other
bin when is_binary(bin) -> Plug.HTML.html_escape_to_iodata(bin)
other -> Phoenix.HTML.Safe.to_iodata(other)
end
end
@doc false
def changed_assign?(changed, name) do
case changed do
%{^name => _} -> true
%{} -> false
nil -> true
end
end
defp changed_assign(changed, name) do
case changed do
%{^name => value} -> value
%{} -> false
nil -> true
end
end
@doc false
def nested_changed_assign?(assigns, changed, head, tail),
do: nested_changed_assign(assigns, changed, head, tail) != false
defp nested_changed_assign(assigns, changed, head, tail) do
case changed do
%{^head => changed} ->
case assigns do
%{^head => assigns} -> recur_changed_assign(assigns, changed, tail)
%{} -> true
end
%{} ->
false
nil ->
true
end
end
defp recur_changed_assign(assigns, changed, [{:struct, head} | tail]) do
recur_changed_assign(assigns, changed, head, tail)
end
defp recur_changed_assign(assigns, changed, [{:access, head} | tail]) do
if match?(%_{}, assigns) or match?(%_{}, changed) do
true
else
recur_changed_assign(assigns, changed, head, tail)
end
end
defp recur_changed_assign(assigns, changed, head, []) do
case {assigns, changed} do
{%{^head => value}, %{^head => value}} -> false
{_, %{^head => value}} when is_map(value) -> value
{_, _} -> true
end
end
defp recur_changed_assign(assigns, changed, head, tail) do
case {assigns, changed} do
{%{^head => assigns_value}, %{^head => changed_value}} ->
recur_changed_assign(assigns_value, changed_value, tail)
{_, _} ->
true
end
end
@doc false
def fetch_assign!(assigns, key) do
case assigns do
%{^key => val} ->
val
%{} when key == :inner_block ->
raise ArgumentError, """
assign @#{key} not available in template.
This means a component requires a do-block or HTML children to
be given as argument but none were given. For example, instead of:
<.component />
You must do:
<.component>
more content
</.component>
Available assigns: #{inspect(Enum.map(assigns, &elem(&1, 0)))}
"""
%{} ->
raise ArgumentError, """
assign @#{key} not available in template.
Please make sure all proper assigns have been set. If you are
calling a component, make sure you are passing all required
assigns as arguments.
Available assigns: #{inspect(Enum.map(assigns, &elem(&1, 0)))}
"""
end
end
# For case/if/unless, we are not leaking the variable given as argument,
# such as `if var = ... do`. This does not follow Elixir semantics, but
# yields better optimizations.
defp classify_taint(:case, [_, _]), do: :live
defp classify_taint(:if, [_, _]), do: :live
defp classify_taint(:unless, [_, _]), do: :live
defp classify_taint(:cond, [_]), do: :live
defp classify_taint(:try, [_]), do: :live
defp classify_taint(:receive, [_]), do: :live
defp classify_taint(:with, _), do: :live
# TODO: Remove me when live_component/2/3 are removed
defp classify_taint(:live_component, [_, [do: _]]), do: :render
defp classify_taint(:live_component, [_, _, [do: _]]), do: :render
defp classify_taint(:inner_block, [_, [do: _]]), do: :render
defp classify_taint(:render_layout, [_, _, _, [do: _]]), do: :render
defp classify_taint(:alias, [_]), do: :always
defp classify_taint(:import, [_]), do: :always
defp classify_taint(:require, [_]), do: :always
defp classify_taint(:alias, [_, _]), do: :always
defp classify_taint(:import, [_, _]), do: :always
defp classify_taint(:require, [_, _]), do: :always
defp classify_taint(:&, [_]), do: :never
defp classify_taint(:for, _), do: :never
defp classify_taint(:fn, _), do: :never
defp classify_taint(_, _), do: :none
end
