add TeX extension with custom jinja filters

README.md

@@ -60,3 +60,23 @@ from flask_tex import run_tex
 
 pdf = run_tex(source, command="pdflatex", directory="/foo/bar/")
 ```
+
+## Jinja integration
+
+For deeper jinja integration, use `flask_tex` as an extension:
+
+```python
+from flask import Flask
+from flask_tex import TeX
+
+app = Flask(__app__)
+TeX(app)
+```
+
+This adds some LaTeX specific filters to the jinja environment.
+
+- LaTeX escape: `{{ foo | latex_escape }}` where `foo = "&$%#_{}"` renders as `"\\&\\$\\%\\#\\_\\{\\}"`.
+    Danger: Do not use this in a html template, because the escaped string is marked as safe
+    with `Markup`, so code that might be dangerous in html does not get escaped.
+
+- LaTeX linebreaks: The `linebreaks` filter converts `\n` into `\\\\\n`.

flask_tex/__init__.py

@@ -2,9 +2,46 @@
 import tempfile
 from subprocess import run, PIPE, CalledProcessError
 
+from markupsafe import Markup
 from flask import render_template, make_response
 
 
+class TexError(Exception):
+    pass
+
+
+class TeX:
+    """TeX Flask extension"""
+
+    def __init__(self, app=None):
+        self.app = app
+        if app:
+            self.init_app(app)
+
+    def init_app(self, app):
+        self.app = app
+
+        app.jinja_env.filters.update(
+            linebreaks=do_linebreaks, latex_escape=do_latex_escape,
+        )
+
+
+def do_linebreaks(value):
+    return value.replace("\n", "\\\\\n")
+
+
+def do_latex_escape(value):
+    return Markup(
+        value.replace("&", "\\&")
+        .replace("$", "\\$")
+        .replace("%", "\\%")
+        .replace("#", "\\#")
+        .replace("_", "\\_")
+        .replace("{", "\\{")
+        .replace("}", "\\}")
+    )
+
+
 def render_to_pdf(template_name, filename="flask.pdf", **kwargs):
     source = render_template(template_name, **kwargs)
     pdf = compile_source(source)
@@ -14,10 +51,6 @@ def render_to_pdf(template_name, filename="flask.pdf", **kwargs):
     return response
 
 
-class TexError(Exception):
-    pass
-
-
 def compile_source(source, command="pdflatex"):
     with tempfile.TemporaryDirectory() as tempdir:
         return run_tex(source, command, tempdir)

tests/test_tex.py

@@ -1,9 +1,9 @@
 import pytest
 from subprocess import CalledProcessError
 
-from flask import Flask
+from flask import Flask, render_template_string, render_template
 
-from flask_tex import compile_source, TexError, render_to_pdf
+from flask_tex import compile_source, TexError, render_to_pdf, TeX
 
 
 class TestRunTex:
@@ -48,3 +48,38 @@ def test_render_template_to_pdf(self):
             rv = render_to_pdf("test.tex", foo="bar")
 
         assert rv.status_code == 200
+
+    def test_no_autoescaping_in_tex_templates(self):
+        app = Flask(__name__)
+
+        with app.test_request_context():
+            rv = render_template("test.tex", foo="This \\& sign will not be escaped")
+
+        assert "This \\& sign will not be escaped" in rv
+
+    def test_newline_filter(self):
+        app = Flask(__name__)
+        TeX(app)
+
+        template_string = "{{ foo | linebreaks }}"
+
+        foo = "bar\nbaz"
+
+        with app.test_request_context():
+            rv = render_template_string(template_string, foo=foo)
+
+        assert rv == "bar\\\\\nbaz"
+
+    def test_latex_escape(self):
+        app = Flask(__name__)
+        TeX(app)
+
+        template_string = "{{ foo | latex_escape }}"
+        foo = "&$%#_{}"
+
+        with app.test_request_context():
+            rv = render_template_string(template_string, foo=foo)
+
+        assert (
+            rv == "\\&\\$\\%\\#\\_\\{\\}"
+        )  # This works because latex_escape marks the escaped string as safe with `Markup`