1b702a2ae3
added tutorial, racket categories relabeled some other categories normalized manual names: de-bolded, changed some names
380 lines
12 KiB
Racket
380 lines
12 KiB
Racket
#lang scribble/doc
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@(require scribble/manual
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scribble/struct
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scribble/eval
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(for-label scheme/base
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macro-debugger/expand
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macro-debugger/emit
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macro-debugger/stepper
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macro-debugger/stepper-text
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macro-debugger/syntax-browser
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(rename-in scheme (free-identifier=? module-identifier=?))))
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@(define the-eval
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(let ([the-eval (make-base-eval)])
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(the-eval '(require macro-debugger/expand
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macro-debugger/stepper-text))
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the-eval))
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@title{Macro Debugger: Inspecting Macro Expansion}
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@author["Ryan Culpepper"]
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The macro-debugger collection contains two tools: a stepper for macro
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expansion and a standalone syntax browser. The macro stepper shows the
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programmer the expansion of a program as a sequence of rewriting
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steps, using the syntax browser to display the individual terms. The
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syntax browser uses colors and a properties panel to show the term's
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syntax properties, such as lexical binding information and source
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location.
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@section{Macro stepper}
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@defmodule[macro-debugger/stepper]
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@defproc[(expand/step [stx any/c])
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void?]{
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Expands the syntax (or S-expression) and opens a macro stepper frame
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for stepping through the expansion.
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}
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@defproc[(expand-module/step [mod module-path?])
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void?]{
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Expands the source file named by @racket[mod], which must contains a
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single module declaration, and opens a macro stepper frame for
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stepping through the expansion.
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}
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@section{Macro expansion tools}
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@defmodule[macro-debugger/expand]
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This module provides @racket[expand]-like procedures that allow the
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user to specify macros whose expansions should be hidden.
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Warning: because of limitations in the way macro expansion is
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selectively hidden, the resulting syntax may not evaluate to the same
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result as the original syntax.
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@defproc[(expand-only [stx any/c] [transparent-macros (listof identifier?)])
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syntax?]{
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Expands the given syntax @racket[stx], but only shows the expansion
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of macros whose names occur in @racket[transparent-macros].
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@(examples #:eval the-eval
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(syntax->datum
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(expand-only #'(let ([x 1] [y 2]) (or (even? x) (even? y)))
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(list #'or))))
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}
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@defproc[(expand/hide [stx any/c] [hidden-macros (listof identifier?)])
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syntax?]{
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Expands the given syntax @racket[stx], but hides the expansion of macros in the
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given identifier list (conceptually, the complement of expand-only).
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@(examples #:eval the-eval
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(syntax->datum
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(expand/hide #'(let ([x 1] [y 2]) (or (even? x) (even? y)))
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(list #'or))))
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}
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@defproc[(expand/show-predicate [stx any/c] [show? (-> identifier? boolean?)])
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syntax?]{
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Expands the given syntax @racket[stx], but only shows the expansion of macros
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whose names satisfy the predicate @racket[show?].
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@(examples #:eval the-eval
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(syntax->datum
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(expand/show-predicate
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#'(let ([x 1] [y 2]) (or (even? x) (even? y)))
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(lambda (id) (memq (syntax-e id) '(or #%app))))))
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}
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@section{Macro stepper API for macros}
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@defmodule[macro-debugger/emit]
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Macros can explicitly send information to a listening macro stepper by
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using the procedures in this module.
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@defproc[(emit-remark [fragment (or/c syntax? string?)] ...
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[#:unmark? unmark? boolean? #t])
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void?]{
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Emits an event to the macro stepper (if one is listening) containing
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the given strings and syntax objects. The macro stepper displays a
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remark by printing the strings and syntax objects above a rendering of
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the macro's context. The remark is only displayed if the macro that
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emits it is considered transparent by the hiding policy.
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By default, syntax objects in remarks have the transformer's mark
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applied (using @racket[syntax-local-introduce]) so that their
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appearance in the macro stepper matches their appearance after the
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transformer returns. Unmarking is suppressed if @racket[unmark?] is
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@racket[#f].
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@racketblock[
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(define-syntax (mymac stx)
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(syntax-case stx ()
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[(_ x y)
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(emit-remark "I got some arguments!"
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#'x
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"and"
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#'y)
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#'(list 'x 'y)]))
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(mymac 37 (+ 1 2))
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]
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(Run the fragment above in the macro stepper.)
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}
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@defproc[(emit-local-step [before syntax?] [after syntax?]
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[#:id id identifier?])
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void?]{
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Emits an event that simulates a local expansion step from
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@racket[before] to @racket[after].
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The @racket[id] argument acts as the step's ``macro'' for the purposes
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of macro hiding.
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}
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@section{Macro stepper text interface}
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@defmodule[macro-debugger/stepper-text]
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@defproc[(expand/step-text [stx any/c]
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[show? (or/c (-> identifier? boolean?)
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(listof identifier?))
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(lambda (x) #t)])
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void?]{
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Expands the syntax and prints the macro expansion steps. If the
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identifier predicate is given, it determines which macros are shown
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(if absent, all macros are shown). A list of identifiers is also
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accepted.
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@(examples #:eval the-eval
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(expand/step-text #'(let ([x 1] [y 2]) (or (even? x) (even? y)))
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(list #'or))
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#;(expand/step-text #'(let ([x 1]) (even? x)))
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#;(expand/step-text #'(let ([x 1] [y 2]) (or (even? x) (even? y)))
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(lambda (id) (eq? (syntax-e id) 'or))))
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}
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@defproc[(stepper-text [stx any/c]
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[show? (or/c (-> identifier? boolean?)
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(listof identifier?))
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(lambda (x) #t)])
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(symbol? -> void?)]{
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Returns a procedure that can be called on the symbol
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@racket['next] to print the next step or on the symbol
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@racket['all] to print out all remaining steps.
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}
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@section{Syntax browser}
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@defmodule[macro-debugger/syntax-browser]
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@defproc[(browse-syntax [stx syntax?])
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void?]{
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Creates a frame with the given syntax object shown. More information
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on using the GUI is available below.
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}
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@defproc[(browse-syntaxes [stxs (listof syntax?)])
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void?]{
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Like @racket[browse-syntax], but shows multiple syntax objects in
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the same frame. The coloring partitions are shared between the two,
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showing the relationships between subterms in different syntax
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objects.
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}
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@section{Using the macro stepper}
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@subsection{Navigation}
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The stepper presents expansion as a linear sequence of rewriting
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process, and it gives the user controls to step forward or backwards
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as well as to jump to the beginning or end of the expansion process.
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If the macro stepper is showing multiple expansions, then it also
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provides ``Previous term'' and ``Next term'' buttons to go up and down in
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the list of expansions. Horizontal lines delimit the current expansion
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from the others.
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@subsection{Macro hiding}
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Macro hiding lets one see how expansion would look if certain macros
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were actually primitive syntactic forms. The macro stepper skips over
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the expansion of the macros you designate as opaque, but it still
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shows the expansion of their subterms.
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The bottom panel of the macro stepper controls the macro hiding
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policy. The user changes the policy by selecting an identifier in the
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syntax browser pane and then clicking one of ``Hide module'', ``Hide
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macro'', or ``Show macro''. The new rule appears in the policy display,
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and the user may later remove it using the "Delete" button.
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The stepper also offers coarser-grained options that can hide
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collections of modules at once. These options have lower precedence
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than the rules above.
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Macro hiding, even with no macros marked opaque, also hides certain
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other kinds of steps: internal defines are not rewritten to letrecs,
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begin forms are not spliced into module or block bodies, etc.
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@section{Using the syntax browser}
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@subsection{Selection}
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The selection is indicated by bold text.
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The user can click on any part of a subterm to select it. To select a
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parenthesized subterm, click on either of the parentheses. The
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selected syntax is bolded. Since one syntax object may occur inside of
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multiple other syntax objects, clicking on one occurrence will cause
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all occurrences to be bolded.
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The syntax browser displays information about the selected syntax
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object in the properties panel on the right, when that panel is
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shown. The selected syntax also determines the highlighting done by
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the secondary partitioning (see below).
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@subsection{Primary partition}
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The primary partition is indicated by foreground color.
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The primary partitioning always assigns two syntax subterms the same
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color if they have the same marks. In the absence of unhygienic
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macros, this means that subterms with the same foreground color were
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either present in the original pre-expansion syntax or generated by
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the same macro transformation step.
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Syntax colored in black always corresponds to unmarked syntax. Such
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syntax may be original, or it may be produced by the expansion of a
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nonhygienic macro.
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Note: even terms that have the same marks might not be
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@racket[bound-identifier=?] to each other, because they might occur in
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different environments.
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@;@example[(bound-identifier=? (let ([x 1]) #'x) #'x)]
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@subsection{Secondary partitioning}
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The user may select a secondary partitioning through the Syntax
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menu. This partitioning applies only to identifiers. When the user
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selects an identifier, all terms in the same equivalence class as the
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selected term are highlighted in yellow.
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The available secondary partitionings are:
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@itemize[
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@item{@racket[bound-identifier=?]}
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@item{@racket[free-identifier=?]}
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]
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@subsection{Properties}
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When the properties pane is shown, it displays properties of the
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selected syntax object. The properties pane has two tabbed pages:
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@itemize[
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@item{@bold{Term}:
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If the selection is an identifier, shows the binding information
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associated with the syntax object. For more information, see
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@racket[identifier-binding], etc.
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}
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@item{@bold{Syntax Object}:
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Displays source location information and other properties (see
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@racket[syntax-property]) carried by the syntax object.
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}
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]
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@subsection{Interpreting syntax}
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The binding information of a syntax object may not be the same as
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the binding structure of the program it represents. The binding
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structure of a program is only determined after macro expansion is
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complete.
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@section{Checking requires}
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@section-index["useless-requires"]
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@defmodule[macro-debugger/analysis/check-requires]
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@defproc[(check-requires [module-name module-path?])
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(listof (list/c 'keep module-path-index? number? (or/c string? #f))
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(list/c 'bypass module-path-index? number?)
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(list/c 'drop module-path-index? number?))]{
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Estimate a module's useless requires.
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The procedure returns one element per (non-label) require in the
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following format:
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@itemlist[
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@item{
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@racket['keep] @racket[module] at @racket[phase] @racket[(optional-comment)]
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@itemlist[
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@item{The require must be kept because bindings defined within it are used.}
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@item{The optional comment indicates if the require must be kept
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@itemlist[
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@item{only because its bindings are re-exported}
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@item{only because the whitelist DB says so}
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]}]}
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@item{
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@racket['bypass] @racket[module] at @racket[phase]
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@itemlist[
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@item{The require is used, but only for bindings that could be more
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directly obtained via another module. For example, @racket[racket]
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can be bypassed in favor of some subset of @racket[racket/base],
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@racket[racket/contract], etc.}]}
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@item{
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@racket['drop] @racket[module] at @racket[phase]
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@itemlist[
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@item{The require appears to be unused. Unless it must be kept for side
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effects or for bindings of a very unusual macro, it can be dropped
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entirely.}]}]
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Examples:
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@racketblock[
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(check-requires 'typed-scheme)
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(check-requires 'unstable/markparam)
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(check-requires 'macro-debugger/syntax-browser/widget)
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]
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}
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A scripting interface to @racket[macro-debugger/analysis/check-requires]
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usable from the command-line is available at
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@racket[macro-debugger/analysis/check-requires-script.rkt].
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Example (from racket root directory):
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@commandline{racket -l macro-debugger/analysis/check-requires-script \
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collects/syntax/*.rkt}
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@defproc[(show-requires [module-name module-path?])
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(listof (list/c 'keep module-path? number? (or/c string? #f))
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(list/c 'bypass module-path? number?)
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(list/c 'drop module-path? number?))]{
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Similar to @racket[check-requires], but outputs module paths instead of
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module path indexes, for more readability.
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}
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