✨ Adding a replace_section helper (#60)

* ✨ Adding a replace_section helper * 🎨 Add a remove_boundaries parameter
davidB · Aug 22, 2023 · 75ba16e · 75ba16e
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diff --git a/Cargo.toml b/Cargo.toml
@@ -46,6 +46,7 @@ toml = { version = "^0.7", optional = true, features = ["preserve_order"] }
 spectral = "0.6"
 tempfile = "3.1"
 pretty_assertions = "1.1"
+similar-asserts = "1.4"
 unindent = "0.2"
 
 [features]

diff --git a/README.md b/README.md
@@ -329,3 +329,53 @@ Helper able to assign (to set) a variable to use later in the template.
 | `{{ assign "foo" "hello world" }}{{ foo }}` | `hello world` |
 | `{{ assign "foo" {} }}{{ foo }}`            | `[object]`    |
 | `{{ assign "foo" {"bar": 33} }}{{ foo }}`   | `[object]`    |
+
+## Replace section
+
+Helper able to replace a section delimited by a boundary.
+
+For example with this template:
+
+```handlebars
+{{~#replace_section  begin="<!-- #region head-->" end="<!-- #endregion head -->" content }}
+This is the new content of the block
+{{~/replace_section}}
+```
+
+And the `content` having
+
+```html
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Document</title>
+  </head>
+  <body>
+    <!-- #region head-->
+    Something by default
+    <!-- #endregion head -->
+  </body>
+</html>
+```
+
+The content between `<!-- #region head-->` and `<!-- #endregion head -->` is replaced by the result of the inner template:
+
+```html
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Document</title>
+  </head>
+  <body>
+    <!-- #region head-->This is the new content of the block<!-- #endregion head -->
+  </body>
+</html>
+```
+
+Note: you can remove the boundary by adding `remove_boundaries=true`.
diff --git a/src/lib.rs b/src/lib.rs
@@ -24,6 +24,7 @@ pub mod outputs;
 pub mod path_helpers;
 #[cfg(feature = "string")]
 pub mod string_helpers;
+pub mod region_helpers;
 
 #[derive(Debug, Error)]
 enum HelperError {
@@ -60,6 +61,7 @@ pub fn register(handlebars: &mut Handlebars) {
     jsonnet_helpers::register(handlebars);
     assign_helpers::register(handlebars);
     file_helpers::register(handlebars);
+    region_helpers::register(handlebars);
 }
 
 #[cfg(test)]

diff --git a/src/region_helpers.rs b/src/region_helpers.rs
@@ -0,0 +1,169 @@
+use handlebars::{
+    Context, Handlebars, Helper, HelperDef, HelperResult, Output, RenderContext, Renderable,
+};
+use log::warn;
+
+pub fn register(handlebars: &mut Handlebars) {
+    handlebars.register_helper("replace_section", Box::new(ReplaceSectionHelper))
+}
+
+#[derive(Clone, Copy)]
+pub struct ReplaceSectionHelper;
+
+impl HelperDef for ReplaceSectionHelper {
+    fn call<'reg: 'rc, 'rc>(
+        &self,
+        h: &Helper<'reg, 'rc>,
+        hbs: &'reg Handlebars<'reg>,
+        ctx: &'rc Context,
+        rc: &mut RenderContext<'reg, 'rc>,
+        out: &mut dyn Output,
+    ) -> HelperResult {
+        let Some(tmpl) = h.template() else {
+            warn!("`replace_section` helper require a template");
+            return Ok(());
+        };
+
+        let Some(input) = h.param(0).and_then(|it| it.value().as_str())  else {
+            warn!("`replace_section` helper require an string parameter");
+            return Ok(());
+        };
+
+        let remove_boundaries = h
+            .hash_get("remove_boundaries")
+            .and_then(|it| it.value().as_bool())
+            .unwrap_or_default();
+
+        let Some(begin) = h.hash_get("begin").and_then(|it| it.value().as_str()) else {
+            warn!("`replace_section` helper require a 'begin' string value");
+            return Ok(());
+        };
+        let Some((before, inner)) = input.split_once(begin) else {
+            warn!("Begin region '{begin}' not found in '{input}'");
+            return Ok(())
+        };
+
+        let Some(end) = h.hash_get("end").and_then(|it| it.value().as_str()) else {
+            warn!("`replace_section` helper require a 'end' string value ");
+            return Ok(());
+        };
+        let Some((_, after)) = inner.split_once(end) else {
+            warn!("End region '{end}' not found in '{inner}'");
+            return Ok(())
+        };
+
+        out.write(before)?;
+        if !remove_boundaries {
+            out.write(begin)?;
+        }
+        tmpl.render(hbs, ctx, rc, out)?;
+        if !remove_boundaries {
+            out.write(end)?;
+        }
+        out.write(after)?;
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::error::Error;
+
+    use serde_json::json;
+    use similar_asserts::assert_eq;
+
+    use crate::new_hbs;
+
+    const INPUT: &str = r#"
+<!DOCTYPE html>
+<html lang="en">
+    <head>
+    <meta charset="UTF-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Document</title>
+    </head>
+    <body>
+    <!-- #region head-->
+    Something by default
+    <!-- #endregion head -->
+    </body>
+</html>
+"#;
+
+    #[test]
+    fn test_helper_replace_section() -> Result<(), Box<dyn Error>> {
+        let data = json!({
+            "content": INPUT,
+        });
+        let mut hbs = new_hbs();
+        hbs.register_template_string(
+            "test",
+            r#"{{#replace_section  begin="<!-- #region head-->" end="<!-- #endregion head -->" content }}
+
+    This is the new content of the block
+    {{/replace_section}}"#,
+        )?;
+
+        let result = hbs.render("test", &data)?;
+
+        assert_eq!(
+            result,
+            r#"
+<!DOCTYPE html>
+<html lang="en">
+    <head>
+    <meta charset="UTF-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Document</title>
+    </head>
+    <body>
+    <!-- #region head-->
+    This is the new content of the block
+    <!-- #endregion head -->
+    </body>
+</html>
+"#,
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_helper_replace_section_remove_remove_boundaries() -> Result<(), Box<dyn Error>> {
+        let data = json!({
+            "content": INPUT,
+        });
+        let mut hbs = new_hbs();
+        hbs.register_template_string(
+            "test",
+            r#"{{~#replace_section  begin="<!-- #region head-->" end="<!-- #endregion head -->" remove_boundaries=true content }}
+This is the new content of the block
+{{~/replace_section}}"#,
+        )?;
+
+        let result = hbs.render("test", &data)?;
+
+        assert_eq!(
+            result,
+            r#"
+<!DOCTYPE html>
+<html lang="en">
+    <head>
+    <meta charset="UTF-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Document</title>
+    </head>
+    <body>
+    This is the new content of the block
+    </body>
+</html>
+"#,
+        );
+
+        Ok(())
+    }
+}