added substution

Author: willmcgugan

docs/guide/content.md

@@ -112,7 +112,7 @@ Auto-closing tags recommended when it is clear which tag they are intended to cl
 
 ### Styles
 
-Tags may contain any number of the following tags:
+Tags may contain any number of the following values:
 
 | Style       | Abbreviation | Description                                                                                                                                               |
 | ----------- | ------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------- |
@@ -267,9 +267,6 @@ For instance, the following create a clickable link:
 This will produce the following output:
 <code><pre><a href="https://www.willmcgugan.com">Visit my blog!</a></pre></code>
 
-
-
-
 ## Content class
 
 Under the hood, Textual will convert markup into a [Content][textual.content.Content] instance.

src/textual/_markup_playground.py

@@ -1,7 +1,9 @@
-from rich.highlighter import ReprHighlighter
+import json
 
 from textual import containers, on
 from textual.app import App, ComposeResult
+from textual.content import Content
+from textual.reactive import reactive
 from textual.widgets import Static, TextArea
 
 
@@ -10,15 +12,26 @@ class MarkupPlayground(App):
     TITLE = "Markup Playground"
     CSS = """
     Screen {
+        & > * {
+            margin: 0 1;
+        }
         layout: vertical;
         #editor {            
             height: 1fr;
             border: tab $primary;  
             padding: 1;
-            margin: 1 1 0 1;
+            margin: 1 1 0 0;
         }
-        #results-container {
-            margin: 0 1;
+        #variables {
+            height: 1fr;
+            border: tab $primary;  
+            padding: 1;
+            margin: 1 0 0 1;
+        }
+        #variables.-bad-json {
+            border: tab $error;
+        }
+        #results-container {           
             border: tab $success;                
             &.-error {
                 border: tab $error;
@@ -32,22 +45,30 @@ class MarkupPlayground(App):
     }
     """
 
+    variables: reactive[dict[str, object]] = reactive({})
+
     def compose(self) -> ComposeResult:
-        yield (text_area := TextArea(id="editor"))
-        text_area.border_title = "Markup"
+        with containers.HorizontalScroll():
+            yield (editor := TextArea(id="editor"))
+            yield (variables := TextArea(id="variables", language="json"))
+        editor.border_title = "Markup"
+        variables.border_title = "Variables (JSON)"
 
         with containers.VerticalScroll(id="results-container") as container:
             yield Static(id="results")
         container.border_title = "Output"
 
-    @on(TextArea.Changed)
+    @on(TextArea.Changed, "#editor")
     def on_markup_changed(self, event: TextArea.Changed) -> None:
+        self.update_markup()
+
+    def update_markup(self) -> None:
         results = self.query_one("#results", Static)
+        editor = self.query_one("#editor", TextArea)
         try:
-            results.update(event.text_area.text)
+            content = Content.from_markup(editor.text, **self.variables)
+            results.update(content)
         except Exception as error:
-            highlight = ReprHighlighter()
-            # results.update(highlight(str(error)))
             from rich.traceback import Traceback
 
             results.update(Traceback())
@@ -57,3 +78,21 @@ def on_markup_changed(self, event: TextArea.Changed) -> None:
             )
         else:
             self.query_one("#results-container").remove_class("-error")
+
+    def watch_variables(self, variables: dict[str, object]) -> None:
+        self.update_markup()
+
+    @on(TextArea.Changed, "#variables")
+    def on_variables_change(self, event: TextArea.Changed) -> None:
+        variables_text_area = self.query_one("#variables", TextArea)
+        try:
+            variables = json.loads(variables_text_area.text)
+        except Exception as error:
+            if not variables_text_area.has_class("-bad-json"):
+                self.notify(f"Bad JSON: ${error}", title="Variables", severity="error")
+                variables_text_area.add_class("-bad-json")
+        else:
+            if variables_text_area.has_class("-bad-json"):
+                variables_text_area.remove_class("-bad-json")
+                self.notify("JSON parsed correctly", title="Variables")
+            self.variables = variables

src/textual/content.py

@@ -168,17 +168,18 @@ def markup(self) -> str:
         return markup
 
     @classmethod
-    def from_markup(cls, markup: str | Content) -> Content:
+    def from_markup(cls, markup: str | Content, **variables: object) -> Content:
         """Create content from Textual markup.
 
-        If `markup` is already Content, return it unmodified.
+        If `markup` is already a Content instance, return it unmodified.
 
         !!! note
-            Textual markup is not the same as Rich markup. Use [Text.parse] to parse Rich Console markup.
+            Textual markup is not the same as Rich markup. Use [Text.parse][rich.text.Text.parse] to parse Rich Console markup.
 
 
         Args:
             markup: Textual markup, or Content.
+            **variables: Optional template variables used
 
         Returns:
             New Content instance.
@@ -188,7 +189,7 @@ def from_markup(cls, markup: str | Content) -> Content:
             return markup
         from textual.markup import to_content
 
-        content = to_content(markup)
+        content = to_content(markup, template_variables=variables or None)
         return content
 
     @classmethod

src/textual/css/parse.py

@@ -405,7 +405,6 @@ def substitute_references(
                                 )
                             )
                     else:
-                        1 / 0
                         _unresolved(ref_name, variables.keys(), token)
                 else:
                     variable_tokens.append(token)
@@ -423,7 +422,6 @@ def substitute_references(
                         ReferencedBy(variable_name, ref_location, ref_length, ref_code)
                     )
             else:
-                1 / 0
                 _unresolved(variable_name, variables.keys(), token)
         else:
             yield token

src/textual/markup.py

@@ -5,7 +5,8 @@
 __all__ = ["MarkupError", "escape", "to_content"]
 
 import re
-from typing import TYPE_CHECKING, Callable, Match
+from string import Template
+from typing import TYPE_CHECKING, Callable, Mapping, Match
 
 from textual._context import active_app
 from textual.color import Color
@@ -271,12 +272,17 @@ def parse_style(style: str, variables: dict[str, str] | None = None) -> Style:
     return parsed_style
 
 
-def to_content(markup: str, style: str | Style = "") -> Content:
+def to_content(
+    markup: str,
+    style: str | Style = "",
+    template_variables: Mapping[str, object] | None = None,
+) -> Content:
     """Convert markup to Content.
 
     Args:
         markup: String containing markup.
         style: Optional base style.
+        template_variables: Mapping of string.Template variables
 
     Raises:
         MarkupError: If the markup is invalid.
@@ -286,18 +292,23 @@ def to_content(markup: str, style: str | Style = "") -> Content:
     """
     _rich_traceback_omit = True
     try:
-        return _to_content(markup, style)
+        return _to_content(markup, style, template_variables)
     except Exception as error:
         # Ensure all errors are wrapped in a MarkupError
         raise MarkupError(str(error)) from None
 
 
-def _to_content(markup: str, style: str | Style = "") -> Content:
+def _to_content(
+    markup: str,
+    style: str | Style = "",
+    template_variables: Mapping[str, object] | None = None,
+) -> Content:
     """Internal function to convert markup to Content.
 
     Args:
         markup: String containing markup.
         style: Optional base style.
+        template_variables: Mapping of string.Template variables
 
     Raises:
         MarkupError: If the markup is invalid.
@@ -310,6 +321,7 @@ def _to_content(markup: str, style: str | Style = "") -> Content:
 
     tokenizer = MarkupTokenizer()
     text: list[str] = []
+    text_append = text.append
     iter_tokens = iter(tokenizer(markup, ("inline", "")))
 
     style_stack: list[tuple[int, str, str]] = []
@@ -321,12 +333,23 @@ def _to_content(markup: str, style: str | Style = "") -> Content:
 
     normalize_markup_tag = Style._normalize_markup_tag
 
+    if template_variables is None:
+        process_text = lambda text: text
+
+    else:
+
+        def process_text(template_text: str, /) -> str:
+            if "$" in template_text:
+                return Template(template_text).safe_substitute(template_variables)
+            return template_text
+
     for token in iter_tokens:
 
         token_name = token.name
         if token_name == "text":
-            text.append(token.value)
-            position += len(token.value)
+            value = process_text(token.value.replace("\\[", "["))
+            text_append(value)
+            position += len(value)
 
         elif token_name == "open_tag":
             tag_text = []

tests/test_markup.py

@@ -73,3 +73,35 @@ def test_content_parse_fail() -> None:
         to_content("[foo]foo[/bar]")
     with pytest.raises(MarkupError):
         to_content("foo[/]")
+
+
+@pytest.mark.parametrize(
+    ["markup", "variables", "content"],
+    [
+        # Simple substitution
+        (
+            "Hello $name",
+            {"name": "Will"},
+            Content("Hello Will"),
+        ),
+        # Wrapped in tags
+        (
+            "Hello [bold]$name[/bold]",
+            {"name": "Will"},
+            Content("Hello Will", spans=[Span(6, 10, style="bold")]),
+        ),
+        # dollar in tags should not trigger substitution.
+        (
+            "Hello [link='$name']$name[/link]",
+            {"name": "Will"},
+            Content("Hello Will", spans=[Span(6, 10, style="link='$name'")]),
+        ),
+    ],
+)
+def test_template_variables(
+    markup: str, variables: dict[str, object], content: Content
+) -> None:
+    markup_content = Content.from_markup(markup, **variables)
+    print(repr(markup_content))
+    print(repr(content))
+    assert markup_content.is_same(content)