Jinja is a great Python template engine.This article explains how to omit the last comma in a series with Jinja.
The desired result is shown below--this is an argument list for an SQL stored procedure. Note that the Id column needs a zero default value and there cannot be a comma after the last column.
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@Id int = 0, @Name nvarchar(100), @PrefixWithThe bit, @Added datetime, @Updated datetime |
In the Libretto SQL Server Json schema there is a columnSqlDeclarations column meta token that produces this:
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@Id int, @Name nvarchar(100), @PrefixWithThe bit, @Added datetime, @Updated datetime, |
That's close, but no cigar. It doesn't assign the zero to the Id column and the trailing comma breaks things.
Assigning a zero to the Id is a special case, so (in my case) its worth a little manual work force the zero assignment (note also that the test for the id column is case insensitive--just in case):
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{% for col in columns %} {% if col.ColumnName.lower() == 'id' %} @{{col.ColumnName}} {{col.DDLType}} = 0 {% else %} @{{col.ColumnName}} {{col.DDLType}} {% endif %} {% endfor %} |
That's close, but the trailing comma remains.
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Id int = 0, @Name nvarchar(100), @PrefixWithThe bit, @Added datetime, @Updated datetime, |
To get the desired result, the template needs omit the trailing comma on the last element in the series. This template:
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{% for col in columns %} {% if col.ColumnName.lower() == 'id' %} @{{col.ColumnName}} {{col.DDLType}} = 0{% if not loop.last %},{% endif %} {% else %} @{{col.ColumnName}} {{col.DDLType}}{% if not loop.last %},{% endif %} {% endif %} {% endfor %} |
produces the correct results:
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@Id int = 0, @Name nvarchar(100), @PrefixWithThe bit, @Added datetime, @Updated datetime |
The Jinja templating engine has a built-in variable that tracks a loop index. The loop.last value conditions when the template emits the comma.
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{% if not loop.last %},{% endif %} |
See the Jinja loop documentation for more info.
While it's not directly a part of this issue, knowing how Jinja controls white space is helpful.
Also, don't miss this Jinja tricks page in the Jinja docs.
