CODEWITHSUNDEEP
jinja2string-formattingwhitespaceindentationtemplate-engine
ttsiodras
ttsiodras

Reputation: 11258

Jinja2 automatic creation of prefix whitespace

In StringTemplate - which I've used in some projects to emit C code - whitespace prefixes are automatically added in the output lines:

PrintCFunction(linesGlobal, linesLocal) ::= <<
void foo() {
    if (someRuntimeFlag) {
        <linesGlobal>
        if (anotherRuntimeFlag) {
            <linesLocal>
        }
    }
}
>>

When this template is rendered in StringTemplate, the whitespace prefixing the multilined linesGlobal and linesLocal strings, is copied for all the lines emitted. The generated C code is e.g.:

void foo() {
    if (someRuntimeFlag) {
        int i;
        i=1;   // <=== whitespace prefix copied in 2nd
        i++;   // <=== and 3rd line
        if (anotherRuntimeFlag) {
            int j=i;
            j++; //  <=== ditto
        }
    }
}

I am new to Jinja2 - and tried to replicate this, to see if I can use Python/Jinja2 to do the same thing:

#!/usr/bin/env python
from jinja2 import Template

linesGlobal='\n'.join(['int i;', 'i=1;'])
linesLocal='\n'.join(['int j=i;', 'j++;'])

tmpl = Template(u'''\
void foo() {
    if (someRuntimeFlag) {
        {{linesGlobal}}
        if (anotherRuntimeFlag) {
            {{linesLocal}}
        }
    }
}
''')

print tmpl.render(
    linesGlobal=linesGlobal,
    linesLocal=linesLocal)

...but saw it produce this:

void foo() {
    if (someRuntimeFlag) {
        int i;
i=1;
        if (anotherRuntimeFlag) {
            int j=i;
j++;
        }
    }
}

...which is not what I want. I managed to make the output emit proper whitespace prefixes with this:

...
if (someRuntimeFlag) {
    {{linesGlobal|indent(8)}}
    if (anotherRuntimeFlag) {
        {{linesLocal|indent(12)}}
    }
}

...but this is arguably bad, since I need to manually count whitespace for every string I emit...

Surely Jinja2 offers a better way that I am missing?

Upvotes: 2

Views: 1228

Answers (1)

ttsiodras
ttsiodras

Reputation: 11258

There's no answer (yet), because quite simply, Jinja2 doesn't support this functionality.

There is, however, an open ticket for this feature - if you care about it, join the discussion there.

Upvotes: 1

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