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instrument.ml
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(* This file is part of Bisect_ppx, released under the MIT license. See
LICENSE.md for details, or visit
https://github.com/aantron/bisect_ppx/blob/master/LICENSE.md. *)
(* Overview
This is the core of Bisect_ppx: the instrumenter that runs on ASTs is defined
here. The instrumenter is divided into two major pieces:
1. The class [instrumenter] traverses ASTs. It decides where instrumentation
should be inserted.
2. The module [Generated_code] provides the helpers that actually insert the
instrumentation. In other words, they insert new leaves into the AST at
the places chosen by [instrumenter].
The code is structured to strongly reflect this division. It is recommended
to read this file with code folding.
Instrumented locations are called {e points}. When the instrumentation code
is executed, the point is {e visited}. Points appear as highlighted
characters in coverage reports.
All state is contained within instances of [instrumenter].
Instances are actually created in [register.ml], which is the "top-level"
side-effecting module of Bisect_ppx, when Bisect_ppx used as a PPX library
(i.e. by PPX drivers).
When Bisect_ppx is used as a standalone executable PPX, the top-level entry
point is in [bisect_ppx.ml]. It's basically a PPX driver that registers only
this instrumenter with itself, using [register.ml], and then runs it. *)
module Parsetree = Ppxlib.Parsetree
module Location = Ppxlib.Location
module Ast_builder = Ppxlib.Ast_builder
module Longident = Ppxlib.Longident
module Pat = Ppxlib.Ast_helper.Pat
module Exp = Ppxlib.Ast_helper.Exp
module Str = Ppxlib.Ast_helper.Str
module Cl = Ppxlib.Ast_helper.Cl
module Cf = Ppxlib.Ast_helper.Cf
(* Can be removed once Bisect_ppx requires OCaml >= 4.08. *)
module Option =
struct
let map f = function
| Some v -> Some (f v)
| None -> None
end
module Coverage_attributes :
sig
val recognize : Parsetree.attribute -> [ `None | `On | `Off | `Exclude_file ]
val has_off_attribute : Parsetree.attributes -> bool
val has_exclude_file_attribute : Parsetree.structure -> bool
end =
struct
let recognize {Parsetree.attr_name; attr_payload; attr_loc} =
if attr_name.txt <> "coverage" then
`None
else
match attr_payload with
| Parsetree.PStr [%str off] ->
`Off
| PStr [%str on] ->
`On
| PStr [%str exclude_file] ->
`Exclude_file
| _ ->
Location.raise_errorf ~loc:attr_loc "Bad payload in coverage attribute."
let has_off_attribute attributes =
(* Don't short-circuit the search, because we want to error-check all
attributes. *)
List.fold_left
(fun found_off attribute ->
match recognize attribute with
| `None ->
found_off
| `Off ->
true
| `On ->
Location.raise_errorf
~loc:attribute.attr_loc "coverage on is not allowed here."
| `Exclude_file ->
(* The only place where [@@@coverage exclude_file] is allowed is the
top-level module of the file. However, if it is there, it will
already have been found by a prescan, Bisect will not be
instrumenting the file, and this function [has_off_attribute] won't
be called. So, if this function ever finds this attribute, it is in
a nested module, or elsewhere where it is not allowed. *)
Location.raise_errorf
~loc:attribute.attr_loc
"coverage exclude_file is not allowed here.")
false attributes
let has_exclude_file_attribute structure =
structure |>
List.exists (function
| {Parsetree.pstr_desc = Pstr_attribute attribute; _}
when recognize attribute = `Exclude_file -> true
| _ -> false)
end
let bisect_file = ref None
let bisect_silent = ref None
let bisect_sigterm = ref false
module Generated_code :
sig
type points
val init : unit -> points
val instrument_expr :
points ->
?override_loc:Location.t ->
?use_loc_of:Parsetree.expression ->
?at_end:bool ->
?post:bool ->
Parsetree.expression ->
Parsetree.expression
val instrument_cases :
points -> ?use_aliases:bool -> Parsetree.case list ->
Parsetree.case list
* Parsetree.case list
* Parsetree.value_binding list
* bool
val runtime_initialization :
points -> string -> Parsetree.structure_item list
end =
struct
type points = {
mutable offsets : int list;
mutable count : int;
}
let init () = {
offsets = [];
count = 0;
}
(* Given an AST for an expression [e], replaces it by the sequence expression
[instrumentation; e], where [instrumentation] is some code that tells
Bisect_ppx, at runtime, that [e] has been visited. *)
let instrument_expr
points ?override_loc ?use_loc_of ?(at_end = false) ?(post = false) e =
let rec outline () =
let loc = choose_location_of_point ~override_loc ~use_loc_of e in
if expression_should_not_be_instrumented ~point_loc:loc ~use_loc_of then
e
else
let point_index = get_index_of_point_at_location ~point_loc:loc in
let open Parsetree in
if not post then
[%expr
___bisect_visit___ [%e point_index];
[%e e]]
else
[%expr
___bisect_post_visit___ [%e point_index] [%e e]]
and choose_location_of_point ~override_loc ~use_loc_of e =
match use_loc_of with
| Some e -> Parsetree.(e.pexp_loc)
| None ->
match override_loc with
| Some override_loc -> override_loc
| _ -> Parsetree.(e.pexp_loc)
and expression_should_not_be_instrumented ~point_loc:loc ~use_loc_of =
let e =
match use_loc_of with
| Some e -> e
| None -> e
in
Location.(loc.loc_ghost) ||
Coverage_attributes.has_off_attribute e.pexp_attributes
and get_index_of_point_at_location ~point_loc:loc =
let point_offset =
if not at_end then
Location.(Lexing.(loc.loc_start.pos_cnum))
else
Location.(Lexing.(loc.loc_end.pos_cnum - 1))
in
let point =
let rec find_point points offset index offsets =
match offsets with
| offset'::_ when offset' = offset -> index
| _::rest -> find_point points offset (index - 1) rest
| [] ->
let index = points.count in
points.offsets <- offset::points.offsets;
points.count <- points.count + 1;
index
in
find_point points point_offset (points.count - 1) points.offsets
in
Ast_builder.Default.eint ~loc point
in
outline ()
(* Instruments a case, as found in [match] and [function] expressions. Cases
contain patterns.
Bisect_ppx treats or-patterns specially. For example, suppose you have
match foo with
| A -> bar
| B -> baz
Both [bar] and [baz] get separate instrumentation points, so that if [A]
is passed, but [B] is never passed, during testing, you will know that [B]
was not tested with.
However, if you refactor to use an or-pattern,
match foo with
| A | B -> bar
and nothing is special is done, the instrumentation point on [bar] covers
both [A] and [B], so you lose the information that [B] is not tested.
The fix for this is a bit tricky, because patterns are not expressions. So,
they can't be instrumented directly. Bisect_ppx instead inserts a special
secondary [match] expression right in front of [bar]:
match foo with
| A | B as ___bisect_matched_value___ ->
(match ___bisect_matched_value___ with
| A -> visited "A"
| B -> visited "B");
bar
So, Bisect_ppx takes that or-pattern [A | B], rotates the "or" out to the
top level (it already is there), splits it into indepedent cases, and
creates a new [match] expression out of them, that allows it to
distinguish, after the fact, which branch was actually taken to reach
[bar].
There are actually several complications to this. The first is that the
generated [match] expression is generally not exhaustive: it only includes
the patterns from the case for which it was generated. This is solved by
adding a catch-all case, and locally suppressing a bunch of warnings:
match foo with
| A | B as ___bisect_matched_value___ ->
(match ___bisect_matched_value___ with
| A -> visited "A"
| B -> visited "B"
| _ (* for C, D, which can't happen here *) -> ())
[@ocaml.warning "..."];
bar
| C | D as ___bisect_matched_value___ ->
(match ___bisect_matched_value___ with
| C -> visited "C"
| D -> visited "D"
| _ (* for A, B, which can't happen here *) -> ())
[@ocaml.warning "..."];;
baz
Next, or-patterns might not be at the top level:
match foo with
| C (A | B) -> bar
has to become
match foo with
| C (A | B) as ___bisect_matched_value___ ->
(match ___bisect_matched_value___ with
| C A -> visited "A"
| C B -> visited "B"
| _ -> ());
bar
This is done by "rotating" the or-pattern to the top level. In this
example, [C (A | B)] is equivalent to [C A | C B]. The latter pattern can
easily be split into cases. This could also be done by aliasing individual
or-patterns, but we did not investigate it.
There might be multiple or-patterns:
match foo with
| C (A | B), D (A | B) -> bar
should become
match foo with
| C (A | B), D (A | B) as ___bisect_matched_value___ ->
(match ___bisect_matched_value___ with
| C A, D A -> visited "A1"; visited "A2"
| C A, D B -> visited "A1"; visited "B2"
| C B, D A -> visited "B1"; visited "A2"
| C B, D B -> visited "B1"; visited "B2"
| _ -> ());
bar
as you can see, or-patterns under and-like patterns (tuples, arrays,
records) get multiplied combinatorially.
The above example also shows that Bisect_ppx needs to mark visisted a
whole list of points in each of the generated cases. For that, the
function that rotates or-patterns to the top level also keeps track of the
original locations of each case of each or-pattern. Each of the resulting
top-level patterns is paired with the list of locations of the or-cases it
contains, visualised above as ["A1"; "A2"], ["A1"; "B2"], etc. These are
termed *location traces*.
Finally, there are some corner cases. First is the exception pattern:
match foo with
| exception (Exit | Failure _) -> bar
should become
match foo with
| exception ((Exit | Failure _) as ___bisect_matched_value___) ->
(match ___bisect_matched_value___ with
| Exit -> visited "Exit"
| Failure _ -> visited "Failure"
| _ -> ());
bar
note that the [as] alias is attached to the payload of [exception], not to
the outer pattern! The latter would be syntactically invalid. Also, we
don't want to generate [exception] cases in the nested [match]: the
exception has already been caught, we are not re-raising and re-catching
it, which just need to know which constructor it was. To deal with this,
we just need to check for the [exception] pattern, and work on its inside
if it is present.
The last corner case is the trivial one. If there no or-patterns, there is
no point in generating a nested [match]:
match foo with
| A as ___bisect_matched_value___ ->
(match ___bisect_matched_value___ with
| A -> visited "A" (* totally redundant *)
| _ -> ());
bar
It's enough to just do
match foo with
| A -> visited "A"; bar
which is pretty much just normal expression instrumentation, though with
location overridden to the location of the pattern.
This is detected when there is only one case after rotating all
or-patterns to the top. If there had been an or-pattern, there would be at
least two cases after rotation.
Handling or-patterns is the most challening thing done here. There are a
few simpler things to consider:
- Pattern guards ([when] clauses) should be instrumented if present.
- We don't instrument [assert false] cases.
- We also don't instrument refutation cases ([| -> .]).
So, without further ado, here is the function that does all this magic: *)
let is_assert_false_or_refutation (case : Parsetree.case) =
match case.pc_rhs with
| [%expr assert false] -> true
| {pexp_desc = Pexp_unreachable; _} -> true
| _ -> false
let insert_instrumentation points (case : Parsetree.case) f =
match case.pc_guard with
| None ->
{case with
pc_rhs = f case.pc_rhs;
}
| Some guard ->
{case with
pc_guard = Some (f guard);
pc_rhs = instrument_expr points case.pc_rhs;
}
let instrumentation_for_location_trace points location_trace e =
location_trace
|> List.sort_uniq (fun l l' ->
l.Location.loc_start.Lexing.pos_cnum -
l'.Location.loc_start.Lexing.pos_cnum)
|> List.fold_left (fun e l ->
instrument_expr points ~override_loc:l e) e
let add_bisect_matched_value_alias loc p =
let open Parsetree in
[%pat? [%p p] as ___bisect_matched_value___]
let generate_nested_match points loc rotated_cases =
rotated_cases
|> List.map (fun (location_trace, rotated_pattern) ->
Exp.case
rotated_pattern
(instrumentation_for_location_trace points location_trace [%expr ()]))
|> fun nested_match_cases ->
nested_match_cases @ [Exp.case [%pat? _] [%expr ()]]
|> Exp.match_ ~loc ([%expr ___bisect_matched_value___])
|> fun nested_match ->
Exp.attr
nested_match
{
attr_name = {txt = "ocaml.warning"; loc};
attr_payload = PStr [[%stri "-4-8-9-11-26-27-28-33"]];
attr_loc = loc
}
(* This function works recursively. It should be called with a pattern [p]
(second argument) and its location (first argument).
It evaluates to a list of patterns. Each of these resulting patterns
contains no nested or-patterns. Joining the resulting patterns in a single
or-pattern would create a pattern equivalent to [p].
Each pattern in the list is paired with a list of locations. These are the
locations of the original cases of or-patterns in [p] that were chosen for
the corresponding result pattern. For example:
C (A | B), D (E | F)
becomes the list of pairs
(C A, D E), [loc A, loc E]
(C A, D F), [loc A, loc F]
(C B, D E), [loc B, loc E]
(C B, D F), [loc B, loc F]
During recursion, the invariant on the location is that it is the location
of the nearest enclosing or-pattern, or the entire pattern, if there is no
enclosing or-pattern. *)
let rotate_or_patterns_to_top loc p =
let rec recur ~enclosing_loc p =
let loc = Parsetree.(p.ppat_loc) in
let attrs = Parsetree.(p.ppat_attributes) in
match p.ppat_desc with
(* If the pattern ends with something trivial, that is not an or-pattern,
and has no nested patterns (so can't have a nested or-pattern), then
that pattern is the only top-level case. The location trace is just the
location of the overall pattern.
Here are some examples of how this plays out. Let's say the entire
pattern was "x". Then the case list will be just "x", with its own
location for the trace.
If the entire pattern was "x as y", this recursive call will return
just "x" with the location of "x as y" for the trace. The wrapping
recursive call will turn the "x" back into "x as y".
If the entire pattern was "A x | B", this recursive call will return
just "x" with the location of "A" (not the whole pattern!). The
wrapping recursive call, for constructor "A", will turn the "x" into
"A x". A yet-higher wrapping recursive call, for the actual or-pattern,
will concatenate this with a second top-level case, corresponding to
"B". *)
| Ppat_any | Ppat_var _ | Ppat_constant _ | Ppat_interval _
| Ppat_construct (_, None) | Ppat_variant (_, None) | Ppat_type _
| Ppat_unpack _ | Ppat_extension _ ->
[([enclosing_loc], p)]
(* Recursively rotate or-patterns in [p'] to the top. Then, for each one,
re-wrap it in an alias pattern. The location traces are not
affected. *)
| Ppat_alias (p', x) ->
recur ~enclosing_loc p'
|> List.map (fun (location_trace, p'') ->
(location_trace, Pat.alias ~loc ~attrs p'' x))
| Ppat_construct (c, Some (ts, p')) ->
recur ~enclosing_loc p'
|> List.map (fun (location_trace, p'') ->
(location_trace,
Pat.mk ~loc ~attrs Pat.(Ppat_construct (c, Some (ts, p'')))))
| Ppat_variant (c, Some p') ->
recur ~enclosing_loc p'
|> List.map (fun (location_trace, p'') ->
(location_trace, Pat.variant ~loc ~attrs c (Some p'')))
| Ppat_constraint (p', t) ->
recur ~enclosing_loc p'
|> List.map (fun (location_trace, p'') ->
(location_trace, Pat.constraint_ ~loc ~attrs p'' t))
| Ppat_lazy p' ->
recur ~enclosing_loc p'
|> List.map (fun (location_trace, p'') ->
(location_trace, Pat.lazy_ ~loc ~attrs p''))
| Ppat_open (c, p') ->
recur ~enclosing_loc p'
|> List.map (fun (location_trace, p'') ->
(location_trace, Pat.open_ ~loc ~attrs c p''))
| Ppat_exception p' ->
recur ~enclosing_loc p'
|> List.map (fun (location_trace, p'') ->
(location_trace, Pat.exception_ ~loc ~attrs p''))
(* Recursively rotate or-patterns in each pattern in [ps] to the top.
Then, take a Cartesian product of the cases, and re-wrap each row in a
replacement tuple pattern.
For example, suppose we have the pair pattern
(A | B, C | D)
The recursive calls will produce lists of rotated cases for each
component pattern:
A | B => [A, loc A]; [B, loc B]
C | D => [C, loc C]; [D, loc D]
We now need every possible combination of one case from the first
component, one case from the second, and so on, and to concatenate all
the location traces accordingly:
[A; C, loc A; loc C]
[A; D, loc A; loc D]
[B; C, loc B; loc C]
[B; D, loc B; loc D]
This is performed by [all_combinations].
Finally, we need to take each one of these rows, and re-wrap the
pattern lists (on the left side) into tuples.
This is typical of "and-patterns", i.e. those that match various
product types (those that carry multiple pieces of data
simultaneously). *)
| Ppat_tuple ps ->
ps
|> List.map (recur ~enclosing_loc)
|> all_combinations
|> List.map (fun (location_trace, ps') ->
(location_trace, Pat.tuple ~loc ~attrs ps'))
| Ppat_record (entries, closed) ->
let labels, ps = List.split entries in
ps
|> List.map (recur ~enclosing_loc)
|> all_combinations
|> List.map (fun (location_trace, ps') ->
(location_trace,
Pat.record ~loc ~attrs (List.combine labels ps') closed))
| Ppat_array ps ->
ps
|> List.map (recur ~enclosing_loc)
|> all_combinations
|> List.map (fun (location_trace, ps') ->
location_trace, Pat.array ~loc ~attrs ps')
(* For or-patterns, recur into each branch. Then, concatenate the
resulting case lists. Don't reassemble an or-pattern. *)
| Ppat_or (p_1, p_2) ->
let ps_1 = recur ~enclosing_loc:p_1.ppat_loc p_1 in
let ps_2 = recur ~enclosing_loc:p_2.ppat_loc p_2 in
ps_1 @ ps_2
(* Performs the Cartesian product operation described at [Ppat_tuple] above,
concatenating location traces along the way.
The argument is rows of top-level case lists (so a list of lists), each
case list resulting from rotating some nested pattern. Since tuples,
arrays, etc., have lists of nested patterns, we have a list of case
lists. *)
and all_combinations = function
| [] -> []
| cases::more ->
let multiply product cases =
product |> List.map (fun (location_trace_1, ps) ->
cases |> List.map (fun (location_trace_2, p) ->
location_trace_1 @ location_trace_2, ps @ [p]))
|> List.flatten
in
let initial =
cases
|> List.map (fun (location_trace, p) -> location_trace, [p])
in
List.fold_left multiply initial more
in
recur ~enclosing_loc:loc p
let rec partition_exceptions (p : Parsetree.pattern) =
match p.ppat_desc with
| Ppat_any | Ppat_var _ | Ppat_alias _ | Ppat_constant _ | Ppat_interval _
| Ppat_tuple _ | Ppat_construct _ | Ppat_variant _ | Ppat_record _
| Ppat_array _ | Ppat_type _ | Ppat_lazy _ | Ppat_unpack _
| Ppat_extension _ ->
Some p, None
| Ppat_exception _ ->
None, Some p
| Ppat_constraint (p', t) ->
let reassemble p' = {p with ppat_desc = Ppat_constraint (p', t)} in
let p_value, p_exception = partition_exceptions p' in
Option.map reassemble p_value, Option.map reassemble p_exception
| Ppat_open (m, p') ->
let reassemble p' = {p with ppat_desc = Ppat_open (m, p')} in
let p_value, p_exception = partition_exceptions p' in
Option.map reassemble p_value, Option.map reassemble p_exception
| Ppat_or (p1, p2) ->
let reassemble p1' p2' =
match p1', p2' with
| None, None -> None
| (Some _ as p1'), None -> p1'
| None, (Some _ as p2') -> p2'
| Some p1', Some p2' -> Some {p with ppat_desc = Ppat_or (p1', p2')}
in
let p1_value, p1_exception = partition_exceptions p1 in
let p2_value, p2_exception = partition_exceptions p2 in
reassemble p1_value p2_value, reassemble p1_exception p2_exception
let rec alias_exceptions loc p =
match Parsetree.(p.ppat_desc) with
| Ppat_any | Ppat_var _ | Ppat_alias _ | Ppat_constant _ | Ppat_interval _
| Ppat_tuple _ | Ppat_construct _ | Ppat_variant _ | Ppat_record _
| Ppat_array _ | Ppat_type _ | Ppat_lazy _ | Ppat_unpack _
| Ppat_extension _ ->
p
| Ppat_or (p_1, p_2) ->
{p with ppat_desc =
Ppat_or (alias_exceptions loc p_1, alias_exceptions loc p_2)}
| Ppat_constraint (p', t) ->
{p with ppat_desc =
Ppat_constraint (alias_exceptions loc p', t)}
| Ppat_exception p' ->
{p with ppat_desc =
Ppat_exception (add_bisect_matched_value_alias loc p')}
| Ppat_open (m, p') ->
{p with ppat_desc =
Ppat_open (m, alias_exceptions loc p')}
let rec drop_exception_patterns p =
match Parsetree.(p.ppat_desc) with
| Ppat_any | Ppat_var _ | Ppat_alias _ | Ppat_constant _ | Ppat_interval _
| Ppat_tuple _ | Ppat_construct _ | Ppat_variant _ | Ppat_record _
| Ppat_array _ | Ppat_type _ | Ppat_lazy _ | Ppat_unpack _
| Ppat_extension _ ->
p (* Should be unreachable. *)
| Ppat_or _ ->
p (* Should be unreachable. *)
(* Dropping exception patterns will change the meaning of type constraints
on them, so drop the type constraints along the way. *)
| Ppat_constraint (p', _) ->
drop_exception_patterns p'
| Ppat_exception p' ->
p'
| Ppat_open (m, p') ->
{p with ppat_desc =
Ppat_open (m, drop_exception_patterns p')}
let rec bound_variables p =
match Parsetree.(p.ppat_desc) with
| Ppat_any | Ppat_constant _ | Ppat_interval _ | Ppat_construct (_, None)
| Ppat_variant (_, None) | Ppat_type _ | Ppat_unpack _ | Ppat_extension _ ->
[]
| Ppat_var x ->
[x]
| Ppat_alias (p', x) ->
x::(bound_variables p')
| Ppat_tuple ps | Ppat_array ps ->
List.map bound_variables ps
|> List.flatten
| Ppat_record (fields, _) ->
List.map (fun (_, p') -> bound_variables p') fields
|> List.flatten
| Ppat_construct (_, Some (_, p')) | Ppat_variant (_, Some p')
| Ppat_constraint (p', _) | Ppat_lazy p' | Ppat_exception p'
| Ppat_open (_, p') ->
bound_variables p'
| Ppat_or (p_1, _) ->
bound_variables p_1 (* Should be unreachable. *)
let rec has_polymorphic_variant p =
match Parsetree.(p.ppat_desc) with
| Ppat_any | Ppat_constant _ | Ppat_interval _ | Ppat_construct (_, None)
| Ppat_unpack _ | Ppat_extension _ | Ppat_var _ ->
false
| Ppat_type _ | Ppat_variant _ ->
true
| Ppat_alias (p', _) | Ppat_construct (_, Some (_, p'))
| Ppat_constraint (p', _) | Ppat_lazy p' | Ppat_exception p'
| Ppat_open (_, p') ->
has_polymorphic_variant p'
| Ppat_tuple ps | Ppat_array ps ->
List.exists has_polymorphic_variant ps
| Ppat_record (fields, _) ->
List.exists (fun (_, p') -> has_polymorphic_variant p') fields
| Ppat_or (p1, p2) ->
has_polymorphic_variant p1 || has_polymorphic_variant p2
let rec make_function loc body = function
| [] ->
Exp.fun_ ~loc Ppxlib.Nolabel None [%pat? ()] body
| x::rest ->
Exp.fun_ ~loc Ppxlib.Nolabel None (Pat.var ~loc x) (make_function loc body rest)
let instrument_cases
points ?(use_aliases = false) (cases : Parsetree.case list) =
let cases =
List.map (fun case ->
case, partition_exceptions case.Parsetree.pc_lhs) cases
in
let use_aliases =
use_aliases || (cases |> List.exists (function
| (_, (Some p, _)) when has_polymorphic_variant p -> true
| _ -> false))
in
cases
|> List.fold_left begin fun
(value_cases, exception_cases, functions, need_binding, index)
((case : Parsetree.case), (value_pattern, exception_pattern)) ->
let loc = case.pc_lhs.ppat_loc in
let case, functions =
match value_pattern, exception_pattern with
| Some p, Some _ ->
let variables = bound_variables p in
let apply loc name =
Exp.apply ~loc
(Exp.ident ~loc {txt = Longident.parse name; loc})
(List.map (fun {Location.loc; txt} ->
Ppxlib.Nolabel,
Exp.ident ~loc {txt = Longident.parse txt; loc})
variables
@ [Ppxlib.Nolabel, [%expr ()]])
in
let case, functions =
match case.pc_guard with
| None ->
case, functions
| Some guard ->
let guard_name = Printf.sprintf "___bisect_guard_%i___" index in
let guard_function =
Ppxlib.Ast_helper.Vb.mk ~loc
(Pat.var ~loc {Location.loc; txt = guard_name})
(make_function loc guard variables)
in
{case with pc_guard = Some (apply guard.pexp_loc guard_name)},
guard_function::functions
in
let case_name = Printf.sprintf "___bisect_case_%i___" index in
let case_function =
Ppxlib.Ast_helper.Vb.mk ~loc
(Pat.var ~loc {Location.loc; txt = case_name})
(make_function loc case.pc_rhs variables)
in
{case with pc_rhs = apply case.pc_rhs.pexp_loc case_name},
case_function::functions
| _ ->
case, functions
in
let value_cases, need_binding =
match value_pattern with
| None -> value_cases, need_binding
| Some p ->
let loc = p.ppat_loc in
let case = {case with pc_lhs = p} in
if is_assert_false_or_refutation case then
case::value_cases, need_binding
else
let case, need_binding =
match rotate_or_patterns_to_top loc p with
| [] ->
insert_instrumentation points
case
(fun e -> instrument_expr points e),
need_binding
| [(location_trace, _)] ->
insert_instrumentation points
case
(instrumentation_for_location_trace points location_trace),
need_binding
| rotated_cases ->
let case =
if use_aliases then
{case with pc_lhs =
add_bisect_matched_value_alias loc case.pc_lhs}
else
case
in
let nested_match =
generate_nested_match points loc rotated_cases in
insert_instrumentation points
case
(fun e -> [%expr [%e nested_match]; [%e e]]),
true
in
case::value_cases, need_binding
in
let exception_cases =
match exception_pattern with
| None -> exception_cases
| Some p ->
let loc = p.Parsetree.ppat_loc in
let case = {case with pc_lhs = p} in
let case =
match rotate_or_patterns_to_top loc p with
| [] ->
insert_instrumentation points
case
(fun e -> instrument_expr points e)
| [(location_trace, _)] ->
insert_instrumentation points
case
(instrumentation_for_location_trace points location_trace)
| rotated_cases ->
let nested_match =
rotated_cases
|> List.map (fun (trace, p) -> trace, drop_exception_patterns p)
|> generate_nested_match points loc
in
insert_instrumentation points
{case with pc_lhs = alias_exceptions loc p}
(fun e -> [%expr [%e nested_match]; [%e e]])
in
case::exception_cases
in
value_cases, exception_cases, functions, need_binding, index + 1
end ([], [], [], false, 0)
|> fun (v, e, f, n, _) ->
List.rev v, List.rev e, List.rev f, n && not use_aliases
let runtime_initialization points file =
let loc = Location.in_file file in
let mangled_module_name =
let buffer = Buffer.create ((String.length file) * 2) in
file |> String.iter (function
| 'A'..'Z' | 'a'..'z' | '0'..'9' | '_' as c ->
Buffer.add_char buffer c
| _ ->
Buffer.add_string buffer "___");
"Bisect_visit___" ^ (Buffer.contents buffer)
in
let points_data =
Ast_builder.Default.pexp_array ~loc
(List.map
(fun offset -> Ast_builder.Default.eint ~loc offset)
(List.rev points.offsets))
in
let filename = Ast_builder.Default.estring ~loc file in
let ast_convenience_str_opt = function
| None ->
Exp.construct ~loc {txt = Longident.parse "None"; loc} None
| Some v ->
Some (Ast_builder.Default.estring ~loc v)
|> Exp.construct ~loc {txt = Longident.parse "Some"; loc}
in
let bisect_file = ast_convenience_str_opt !bisect_file in
let bisect_silent = ast_convenience_str_opt !bisect_silent in
let bisect_sigterm =
let open Parsetree in
if !bisect_sigterm then [%expr true] else [%expr false]
in
(* ___bisect_visit___ is a function with a reference to a point count array.
It is called every time a point is visited.
It is scoped in a local module, to ensure that each compilation unit
calls its own ___bisect_visit___ function. In particular, if
___bisect_visit___ is unscoped, the following interaction is possible
between a.ml and b.ml:
a.ml:
let ___bisect_visit___ = (* ... *)
b.ml:
let ___bisect_visit___ = (* ... *)
open A
(* Further calls to ___bisect_visit___ are to A's instance of it! *)
To prevent this, Bisect_ppx generates:
a.ml:
module Bisect_visit___ =
struct
let ___bisect_visit___ = (* ... *)
end
open Bisect_visit___ (* Scope of open is only a.ml. *)
b.ml:
module Bisect_visit___ =
struct
let ___bisect_visit___ = (* ... *)
end
open Bisect_visit___
(* Since this open is prepended to b.ml, it is guaranteed to precede any
open A. At the same time, open A introduces Bisect_visit___ into
scope, not ___bisect_visit___. So, after this point, any unqualified
reference to ___bisect_visit___ is to b.ml's instance. *)
open A
Bisect_ppx needs to mangle the generated module names, to make them
unique. Otherwise, including A in B triggers a duplicate module
Bisect_visit___ error. This is better than mangling ___bisect_visit___
itself for two reasons:
1. A collision of mangled module names (due to include) is a compile-time
error. By comparison, a collusion of mangled function names will
result in one silently shadowing the other, which *may* produce a
runtime error if (1) the shadowing function has a smaller points array
than the shadowed function and (2) the shadowing function is actually
called with a large enough point index during testing. If shadowing
does not produce a runtime error, it can result in inaccurate coverage
statistics being silently accumulated.
2. ___bisect_visit___, sprinked throughout the code, can be kept
unmangled. This keeps the mangling generation code local to this
instrumentation function, which generates only the top of each
instrumented module. That keeps the instrumenter relatively simple.
For discussion, see
https://github.com/aantron/bisect_ppx/issues/160 *)
let generated_module =
let bisect_visit_function =
let open Parsetree in
[%stri
let ___bisect_visit___ =
let points = [%e points_data] in
let `Visit visit =
Bisect.Runtime.register_file
~bisect_file:[%e bisect_file] ~bisect_silent:[%e bisect_silent]
~filename:[%e filename] ~points ~bisect_sigterm:[%e bisect_sigterm]
in
visit
]
in
let bisect_post_visit =
let open Parsetree in