mark_safe documentation should note that strings will become unsafe if modified.

[dev@…]

This took me a while to figure out what was happening and it would be good to have this documented somewhere.

In [1]: from django.utils.safestring import mark_safe

In [2]: s = "<blink>hello world</blink>    "

In [3]: type(s)
Out[3]: str

In [4]: t = mark_safe(s)

# t is now 'safe': 
In [5]: type(t)
Out[5]: django.utils.safestring.SafeBytes

# let's remove that unnecessary white space....
In [6]: type(t.strip())
Out[6]: str    # and we're not safe anymore.

[Tim Graham]

If you'd like to provide a patch, I'll be happy to review and commit it.

[vijay_shanker]

added a sentence and a code example to how modified strings are not safe

[Tim Graham]

I will go ahead and commit this with the following fixes:

• The patch introduces some undesired whitespace in random places. I suggest you set your edit to remove trailing whitespace.
• The patch uses tabs for indentation; it should use spaces instead.

Tips:

• Don't forget to check "Has patch" on the ticket so it shows up for review.
• Use a diff or patch file extension rather than txt so that Trac does syntax highlighting when viewing the patch.

Thank-you for the contribution.

[Tim Graham <timograham@…>]

In 1edef50880f740e00fa1cd501c2ac56ec6fd10e4:

Fixed #21316 -- Documented that modifying safe strings makes them unsafe.

Thanks dev@… for the suggestion and vijay_shanker for the patch.

[Tim Graham <timograham@…>]

In f832f0d2c309ac31bbf3616c34495c48509b0fb3:

[1.5.x] Fixed #21316 -- Documented that modifying safe strings makes them unsafe.

Thanks dev@… for the suggestion and vijay_shanker for the patch.

Backport of 1edef50880 from master

[Tim Graham <timograham@…>]

In da0c7723fa71f7273d5bd917a6aecc4243232a4e:

[1.6.x] Fixed #21316 -- Documented that modifying safe strings makes them unsafe.

Thanks dev@… for the suggestion and vijay_shanker for the patch.

Backport of 1edef50880 from master