Difference between revisions of "Custom Reports Using Eguile"

Revision as of 13:45, 1 September 2014

What is eguile?

eguile is a way of processing a template file to create a guile script.

More specifically, within GnuCash, guile is used to combine HTML and guile code to create a report, such as an invoice or balance sheet.

The GnuCash version of eguile is eguile-gnc.scm, written in early 2009 by Chris Dennis, and based on Neale Pickett's eguile.scm.

For example,

<h3><?scm:d coyname ?></h3>
<h2><?scm:d reportname ?> as at <?scm:d (gnc-print-date opt-date-tp) ?></h2>

would become

(display "<h3>")(display "Acme Tools Ltd.")(display "</h3>
<h2>)(display "Balance Sheet")(display " as at ")
(display "05/04/2009")(display "<h2">)

which is then evaluated as guile code to create the text of the report.

How to install an eguile report

To try out eguile-based reports, you first need to download eguile-gnc.scm and put it into the report folder. On my system -- Ubuntu -- that's /usr/share/gnucash/guile-modules/gnucash/report/eguile-gnc.scm. In general, it should go into the same folder as files such as fancy-invoice.scm.

Note: GnuCash 2.3/2.4 already includes eguile-gnc.scm.

Install the report and its associated files in the usual way (see Custom Reports#Loading the Report for a full explanation).

(define-module (gnucash report my-report-name))

The easiest way is to put all the files for a report into your .gnucash folder, and then add a line to .gnucash/config.user like this:

(load "/path/to/my/.gnucash/report.scm")  

If .gnucash/config.user does not already exist, just create it and add the new line.

For example, on a Linux system, for a user called 'chris', the Tax Invoice report can be installed by:

1. Downloading taxinvoice.scm and taxinvoice.eguile.scm, and putting them into the /home/chris/.gnucash/ folder.
2. Adding this line to /home/chris/.gnucash/config.user:

(load "/home/chris/.gnucash/taxinvoice.scm")

Restart GnuCash, and the report should then show up somewhere in the reports menu, depending on the menu-path option in the report. The Tax Invoice and Balance Sheet reports (see below) put themselves into the Reports/Business sub-menu.

How to create an eguile report

...

eguile syntax

Within what is otherwise an HTML source file, Guile/Scheme code is wrapped in '<?scm ... ?>' (whitespace is required after '<?scm' and before '?>')

'<?scm ... ?>' pairs can NOT be nested.

The optional :d modifier (i.e. '<?scm:d' ) is just a shortcut for '(display ... )', so '<?scm:d x ?>' is the same as '<?scm (display x) ?>'

Note that s-expressions can be spread across more than one '<?scm ... ?>', for example:

<?scm (if (> x 3) (begin ?>Bigger<?scm ) (begin ?>Smaller<?scm )) ?>

Each chunk of text outside a '<?scm ... ?>' pair ends up wrapped in a (display ... ), after having had double quotes etc. escaped.

The processing happens in two passes. Initially the input file is converted to a Guile script, and then that script is evaluated to produce the final result (as a string which is passed back to the report-displaying part of GnuCash).

For example, if the input file contained these lines:

 <h1 align="center">Invoice <?scm:d invoiceid ?></h1>
 <?scm (for entry in entries do ?>
   <p>Date: <?scm:d (entry date) ?>, description: <?scm:d (entry desc) ?>
 <?scm ) ?>

the resulting script would look like:

 (display "<h1 align=\"center\">Invoice ")(display invoiceid)(display "</h1>")
 (for entry in entries do
   (display "<p>Date: ")(display (entry date))
   (display ", description: ")(display (entry desc))
 )

and the final result might be this:

 <h1 align="center">Invoice 002345</h1>
   <p>Date: 04/03/2009, description: Widgets
   <p>Date: 05/03/2009, description: Modified widgets

...

Custom for-loop syntax

To simply looping over a list or map (which by default is a bit cumbersome in scheme), GnuCash defines a custom for-loop syntax, which works similar to for loops in some imperative languages. There are three forms of this syntax: For a single list, for multiple lists and for hashes. This for loop syntax should be available in all eguile-based reports (both in the report itself as well as in the eguile templates). This syntax is defined in eguile-utilities.scm, so it might be available in other parts of scheme as well.

Single list

(for <var> in <list> do <expr> ...)

This syntax loops over <list>, assigning each value to <var> in turn and evaluating all <expr>'s. In other words, it takes the first element of <list>, assigns it to <var>, evaluates each <expr>, takes the second element of <list>, etc.

Consider the following example:

(for entry in (gncInvoiceGetEntries invoice) do
  (displayEntry entry))

This example would evaluate the "displayEntry" function for each entry in a given invoice.

Multiple lists

(for (<var> ...) in (<list> ...) do <expr> ...)

This syntax loops over all <list>'s in parallel, assigning each value to the corresponding <var> and evaluates all <expr>'s. In other words, it takes the first element of the first <list>, assigns it to the first <var>, takes the first element of the second <list>, assigns it to the second <var>, up to the last <list> and <var>. Then it evaluates each <expr> and starts over with the second element of each list, etc.

Consider the following example:

(let ((descriptions (list "Company name" "Address" "Website"))
      (values (list "Example Corp" "Example street 1" "http://example.org")))
  (for (desc val) in (descriptions values) do
    (display desc)
    (display ": ")
    (display val)
    (display "<br/>\n")))

This example would output:

Website: http://example.org<br/>
Company name: Example Corp<br/>
Address: Example street 1<br/>

Hashes

(for <key> => <value> in <hash> do <expr> ...)

This syntax loops over all keys and values in a hash, assiging each key to <key> and each value to <value> in turn and evaluating all <expr>'s. Note that as always with hashes, the keys from the hash are looped in arbitrary order.

Consider the following example:

(let ((company (make-hash-table 16)))
  (hash-set! company "Company name" "Example Corp")
  (hash-set! company "Address" "Example street 1")
  (hash-set! company "Website" "http://example.org")
  (for desc => val in company do
    (display desc)
    (display ": ")
    (display val)
    (display "<br/>\n")))

This example would output exactly the same as the previous example.

...the rest of this page will be here very soon

Internationalisation

Always use _ rather than N_ in the template file. N_ can be used for report option names, help text, and default values.

More precise N_ means NOP, no operation. It can be used to mark strings for translation e.g. in array declarations, but doesn't translate them. Then later the translation is called with _. More Details in Translation#Tips for Developers.

Changes in Gnucash 2.6

Some changes in Gnucash 2.6 are causing custom reports written for 2.4 to fail. If your custom report does not show up in gnucash this may be why. To find out whether this is indeed the case, run gnucash from the command line and enable logging to stdout:

$ gnucash --logto stdout

Watch whether gnucash complains about gnucash business-utils. If so, remove any references in your custom report to business-utils. This module is now part of the core, so does not need to be included.

Restart gnucash and with some luck your custom report shows up again. You will probably get errors about unbound values. This is because Gnucash 2.6 improved on some functions in src/engine/gncEntry.h . A number of functions have been renamed in the process. The new names you can find by taking a look in the gncEntry.h source file.

Some examples:

2.4: gncEntryReturnValue entry #t 2.6: gncEntryGetDocValue entry #f #t #f

2.4: gncEntryReturnDiscountValue entry #t 2.6: gncEntryGetDocDiscountValue entry #f #t #f

2.4: gncEntryReturnTaxValue entry #t 2.6: gncEntryGetDocTaxValue entry #f #t #f

Available Reports

The following eguile-based reports are available. More will be contributed soon (hopefully).

Note: to make use of the advanced CSS features in Gnucash 2.4, you need to build gnucash with webkit support instead of gtkhtml. More information on how to build gnucash can be found here: Building. (QuickTip: ./configure --with-html-engine=webkit)

Tax Invoice

Features

• Included in the GnuCash source tree
• Includes full company and customer details, including a company logo if required.
• Automatically includes only relevant columns. For example, if none of the items on the invoice have discounts applied, then the discount columns will be omitted.

Issues

• taxinvoice.scm includes code to display individual taxes on a per-entry basis, i.e. on each line of the invoice. This relies on a fix to the Swig encoding that is currently in the pipeline as bug #573645, but it includes a work-around so that it simply misses out the extra columns if that fix hasn't been applied. This bug has been fixed in 2.3/2.4.
• Doesn't have a separate CSS file (yet).

Balance Sheet

Features

• This report has been included in GnuCash.
• Displays the balance sheet in a 'text book' style with rules under columns etc.
• Uses the 'Assets = Equity + Liabilities' model. If there is demand for an 'Assets - Liabilities = Equity' version, then that could be done as a separate report, or by adding an option and some extra code to this one.
• One- or two-column layout.
• Negative values can be shown as, for example, '-£100.00' or '(£100.00)'.
• Deliberately has fewer options than the standard balance sheet. It makes 'intelligent' decisions about what to display. For example, parent accounts that are marked as placeholders and have a zero balance do not have their balance shown at all.
• Handles commodities/currencies in a basic way -- exchange rates are calculated as at the date of the balance sheet.
• A balancing entry (labelled 'Retained Earnings' by default) is calculated so that the sheet always balances.
• Only displays Imbalance and Orphan accounts if non-zero.
• Does not have a account selection option -- I don't see why you would want a balance sheet with some accounts missing.
• Does not deal with unrealised gains/losses.

To Do

• Option to put the currency symbol at the top of each column, rather than on every value.
• Option to put "Less: " in front of negative accounts, e.g.

 Less: Drawings        (£1000.00)

Issues

• Needs people to test it and comment on it.

Proposed Reports

Cash Based Income Statement

Because of the importance and impacts this discussion moved to Cash Based Accounting.