d892cb243e
packaged with the mzscheme distribution * Make scheme/help throw a helpful message if the file is missing svn: r11896
70 lines
2.3 KiB
Scheme
70 lines
2.3 KiB
Scheme
#lang scheme/base
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(require (for-syntax scheme/base) scheme/promise)
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(provide help)
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(define-syntax (help stx)
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(if (identifier? stx)
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#'(open-help-start)
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(syntax-case stx ()
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[(help)
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#'(open-help-start)]
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[(help id)
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(identifier? #'id)
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#'(find-help (quote-syntax id))]
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[(help id #:from lib)
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(if (identifier? #'id)
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(if (module-path? (syntax->datum #'lib))
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#'(find-help/lib (quote id) (quote lib))
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(raise-syntax-error
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#f "expected a module path after #:from" stx #'lib))
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(raise-syntax-error
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#f "expected an identifier before #:from" stx #'id))]
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[(help #:search str ...)
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(with-syntax ([(str ...)
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(map (lambda (e)
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(if (string? (syntax-e e))
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e
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(format "~s" (syntax->datum e))))
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(syntax->list #'(str ...)))])
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#'(search-for (list str ...)))]
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[_
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(raise-syntax-error
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#f
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(string-append "expects a single identifer, a #:from clause, or a"
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" #:search clause; try just `help' for more information")
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stx)])))
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(define (open-help-start)
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(find-help #'help))
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;; Autoload utilities from help/help-utils; if it does not exists,
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;; suggest using docs.plt-scheme.org.
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(define-namespace-anchor anchor)
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(define get-binding
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(let ([ns #f] [utils #f])
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(lambda (sym)
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(unless ns
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(set! ns (namespace-anchor->empty-namespace anchor))
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(set! utils (resolved-module-path-name
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(module-path-index-resolve
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(module-path-index-join 'help/help-utils #f)))))
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(parameterize ([current-namespace ns])
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(if (file-exists? utils)
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(dynamic-require utils sym)
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(lambda _
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(error 'help "documentation system unavailable; ~a\n~a"
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"try http://docs.plt-scheme.org/"
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(format " (missing file: ~a)" utils))))))))
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(define-syntax-rule (define-help-autoload id)
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(define id
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(let ([proc (delay (get-binding 'id))])
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(lambda args (apply (force proc) args)))))
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(define-help-autoload find-help)
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(define-help-autoload find-help/lib)
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(define-help-autoload search-for)
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