### Multiline flow mapping style example

Source: https://docs.rs/yamlpatch/latest/yamlpatch/enum.Style.html

Example of a multiline flow mapping style, as shown in the documentation for the MultilineFlowMapping variant.

```yaml
{
  key: value,
  key2: value2
}
```

--------------------------------

### Multiline flow sequence style example

Source: https://docs.rs/yamlpatch/latest/yamlpatch/enum.Style.html

Example of a multiline flow sequence style, as shown in the documentation for the MultilineFlowSequence variant.

```yaml
[
  item1,
  item2,
]
```

--------------------------------

### YAML rewrite example for RewriteFragment

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Example showing a YAML fragment before and after a rewrite operation, along with the configuration for the rewrite. The operation replaces the first match of 'from' with 'to'.

```yaml
run: |
  echo "foo: ${{ foo }}"
```

```yaml
run: |
  echo "foo ${FOO}"
```

```text
route: "/run",
from: "${{ foo }}",
to: "${FOO}",
```

--------------------------------

### route_to_feature_pretty function

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Queries a YAML document using a route and returns the feature in a pretty format.

```rust
pub fn route_to_feature_pretty<'a>(
    route: &yamlpath::Route<'_>,
    doc: &'a yamlpath::Document,
) -> Result<yamlpath::Feature<'a>, Error> {
    doc.query_pretty(route).map_err(Error::from)
}
```

--------------------------------

### Op::Replace

Source: https://docs.rs/yamlpatch/latest/yamlpatch/enum.Op.html

Replaces the value at the given path.

```APIDOC
## Op::Replace

### Description
Replaces the value at the given path.

### Variant
`Replace(Value)`

### Fields
- **value** (Value) - Required - The new value to replace the existing one.
```

--------------------------------

### Op::Add

Source: https://docs.rs/yamlpatch/latest/yamlpatch/enum.Op.html

Adds a new key-value pair at the given path. The route should point to a mapping. The mapping must be a block mapping or single-line flow mapping; multi-line flow mappings are not supported. The key must not already exist in the targeted mapping.

```APIDOC
## Op::Add

### Description
Adds a new key-value pair at the given path. The route should point to a mapping. The mapping must be a block mapping or single-line flow mapping; multi-line flow mappings are not currently supported. The key must not already exist in the targeted mapping.

### Variant
`Add { key: String, value: Value }`

### Fields
- **key** (String) - Required - The key to add.
- **value** (Value) - Required - The value to associate with the key.

### Limitations
- The mapping must be a block mapping or single-line flow mapping.
- Multi-line flow mappings are not currently supported.
- The key must not already exist in the targeted mapping.
```

--------------------------------

### Rust: handle_block_mapping_addition function

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Formats a new YAML key-value entry for insertion into a block mapping. Serializes the value (using flow style for sequences, otherwise standard YAML serialization), determines indentation from the existing document, and builds the entry string. For empty mappings, formats inline; for non-empty mappings, nests the value with two spaces of indentation per level.

```rust
fn handle_block_mapping_addition(
    feature_content: &str,
    doc: &yamlpath::Document,
    feature: &yamlpath::Feature,
    key: &str,
    value: &yaml_serde::Value,
) -> Result<String, Error> {
    // Convert the new value to YAML string for block style handling
    let new_value_str = if matches!(value, yaml_serde::Value::Sequence(_)) {
        // For sequences, use flow-aware serialization to maintain consistency
        serialize_flow(value)?
    } else {
        serialize_yaml_value(value)?
    };
    let new_value_str = new_value_str.trim_end(); // Remove trailing newline

    // Determine the appropriate indentation
    let indent = " ".repeat(extract_leading_indentation_for_block_item(doc, feature));

    // Format the new entry
    let mut final_entry = if let yaml_serde::Value::Mapping(mapping) = &value {
        if mapping.is_empty() {
            // For empty mappings, format inline
            format!("\n{indent}{key}: {new_value_str}")
        } else {
            // For non-empty mappings, format as a nested structure
            let value_lines = new_value_str.lines();
            let mut result = format!("\n{indent}{key}:");
            for line in value_lines {
                if !line.trim().is_empty() {
                    result.push('\n');
                    result.push_str(&indent);
                    result.push_str("  "); // 2 spaces for nested content
                    // `serialize_yaml_value` anchors its output at column 0, so
                    // each line's own leading whitespace *is* its depth relative
                    // to the value's root. Trimming it here would flatten every
                    // nested level into a sibling of the top-level key.
                    result.push_str(line);
                }
            }
        }
    };
    // ... (rest of function omitted in source)
}
```

--------------------------------

### Op::MergeInto

Source: https://docs.rs/yamlpatch/latest/yamlpatch/enum.Op.html

Updates a mapping at the given path. If the mapping does not already exist, it will be created.

```APIDOC
## Op::MergeInto

### Description
Updates a mapping at the given path. If the mapping does not already exist, it will be created.

### Variant
`MergeInto { key: String, updates: IndexMap<String, Value> }`

### Fields
- **key** (String) - Required - The key of the mapping to update.
- **updates** (IndexMap<String, Value>) - Required - The updates to apply to the mapping.
```

--------------------------------

### route_to_feature_exact function

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Queries a YAML document using a route and returns the exact feature, or None if not found.

```rust
pub fn route_to_feature_exact<'a>(
    route: &yamlpath::Route<'_>,
    doc: &'a yamlpath::Document,
) -> Result<Option<yamlpath::Feature<'a>>, Error> {
    doc.query_exact(route).map_err(Error::from)
}
```

--------------------------------

### Rust: indent_multiline_yaml function

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Indents multi-line YAML content to match a target base indentation. The first line is kept as-is; subsequent non-empty lines are prefixed with the base indent plus two extra spaces. Empty lines are preserved with just the base indent. Returns the original content unchanged if it has one line or fewer.

```rust
fn indent_multiline_yaml(content: &str, base_indent: &str) -> String {
    let lines: Vec<&str> = content.lines().collect();
    if lines.len() <= 1 {
        return content.to_string();
    }

    let mut result = String::new();
    for (i, line) in lines.iter().enumerate() {
        if i == 0 {
            result.push_str(line);
        } else {
            result.push('\n');
            result.push_str(base_indent);
            if !line.trim().is_empty() {
                result.push_str("  "); // Additional indentation for continuation
                result.push_str(line.trim_start());
            }
        }
    }
    result
}
```

--------------------------------

### serialize_flow(value: &Value) -> Result<String, Error>

Source: https://docs.rs/yamlpatch/latest/yamlpatch/fn.serialize_flow.html

Serializes a `yaml_serde::Value` to a YAML string in flow layout. This function supports only a restricted subset of YAML: tags are not supported, and mapping keys must be strings.

```APIDOC
## Function: serialize_flow

### Description
Serializes a `yaml_serde::Value` to a YAML string in flow layout. This function supports only a restricted subset of YAML: tags are not supported, and mapping keys must be strings.

### Signature
rust
pub fn serialize_flow(value: &Value) -> Result<String, Error>


### Parameters
- **value** (`&Value`) - The `yaml_serde::Value` to serialize.

### Returns
- `Result<String, Error>` - On success, returns the YAML string in flow layout. On failure, returns an error.

### Constraints
- Tags are not supported.
- Mapping keys must be strings.

```

--------------------------------

### Op::Remove

Source: https://docs.rs/yamlpatch/latest/yamlpatch/enum.Op.html

Removes the key at the given path.

```APIDOC
## Op::Remove

### Description
Removes the key at the given path.

### Variant
`Remove`
```

--------------------------------

### MergeInto operation handling

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Handles the MergeInto operation, checking if a key exists in a mapping and applying the appropriate patch (Replace or Add). Returns an error if the key exists but has an empty body, and adds the entire update if the key does not exist.

```rust
if existing_mapping.contains_key(k) {
    current_document = apply_single_patch(
        &current_document,
        &Patch {
            route: existing_key_route.with_key(k.as_str()),
            operation: Op::Replace(v.clone()),
        },
    )?;
} else {
    current_document = apply_single_patch(
        &current_document,
        &Patch {
            route: existing_key_route.clone(),
            operation: Op::Add {
                key: k.into(),
                value: v.clone(),
            },
        },
    )?;
}
}

return Ok(current_document);
}
// The key exists, but has an empty body.
// TODO: Support this.
Ok(None) => {
    return Err(Error::InvalidOperation(format!(
        "MergeInto: cannot merge into empty key at {existing_key_route:?}"
    )));
}
// The key does not exist.
Err(Error::Query(yamlpath::QueryError::ExhaustedMapping(_))) => {
    return apply_single_patch(
        document,
        &Patch {
            route: patch.route.clone(),
            operation: Op::Add {
                key: key.clone(),
                value: yaml_serde::to_value(updates.clone())?,
            },
        },
    );
}
Err(e) => return Err(e),
```

--------------------------------

### route_to_feature_pretty

Source: https://docs.rs/yamlpatch/latest/yamlpatch/fn.route_to_feature_pretty.html

Converts a route to a feature representation using a YAML document.

```APIDOC
## Function route_to_feature_pretty

### Description
Converts a route to a feature representation using a YAML document.

### Signature
```rust
pub fn route_to_feature_pretty<'a>(
    route: &Route<'_>,
    doc: &'a Document,
) -> Result<Feature<'a>, Error>
```

### Parameters
- **route** (`&Route<'_>`) - The route to convert.
- **doc** (`&'a Document`) - The YAML document to use for feature extraction.

### Returns
- **Result<Feature<'a>, Error>** - The resulting feature or an error if conversion fails.
```

--------------------------------

### Op::Append

Source: https://docs.rs/yamlpatch/latest/yamlpatch/enum.Op.html

Appends a new item to a sequence at the given path. The sequence must be a block sequence; flow sequences are not supported.

```APIDOC
## Op::Append

### Description
Appends a new item to a sequence at the given path. The sequence must be a block sequence; flow sequences are not supported.

### Variant
`Append { value: Value }`

### Fields
- **value** (Value) - Required - The value to append to the sequence.

### Limitations
- The sequence must be a block sequence.
- Flow sequences are not supported.
```

--------------------------------

### Replace operation implementation

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Handles the Op::Replace operation. It retrieves the feature at the patch route, applies value replacement, and calculates the span to replace, including leading whitespace for key-value pairs.

```rust
Op::Replace(value) => {
    let feature = route_to_feature_pretty(&patch.route, document)?;

    // Get the replacement content
    let replacement = apply_value_replacement(&feature, document, value, true)?;

    // Extract the current content to calculate spans
    let current_content = document.extract(&feature);
    let current_content_with_ws = document.extract_with_leading_whitespace(&feature);

    // Find the span to replace - use the span with leading whitespace if it's a key-value pair
    let (start_span, end_span) = if current_content_with_ws.contains(':') {
        // Replace the entire key-value pair span
        let ws_start = feature.location.byte_span.0
```

--------------------------------

### apply_yaml_patches

Source: https://docs.rs/yamlpatch/latest/yamlpatch/fn.apply_yaml_patches.html

Applies a sequence of YAML patch operations to a YAML document and returns a new YAML document. Returns an error if the input is invalid, a patch operation fails, or the resulting YAML is malformed.

```APIDOC
## apply_yaml_patches

### Description
Applies a sequence of YAML patch operations to a YAML document. Returns a new YAML document with the patches applied. Returns an error if the given YAML input is not valid, if a patch operation fails, or if the resulting YAML is malformed.

### Function Signature
```rust
pub fn apply_yaml_patches(
    document: &Document,
    patches: &[Patch<'_>],
) -> Result<Document, Error>
```

### Parameters
- **document** (`&Document`) - The YAML document to which patches are applied.
- **patches** (`&[Patch<'_>]`) - A slice of patch operations to apply in order.

### Returns
- **Result<Document, Error>** - A new YAML document with the patches applied, or an error if the input is invalid, a patch operation fails, or the resulting YAML is malformed.

### Behavior
Each patch is applied in the order given. The `Patch` APIs are designed to operate symbolically without absolute byte positions, so operations should not invalidate each other unless they actually conflict in terms of proposed changes.
```

--------------------------------

### Handle flow mapping value replacement

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Replaces a value within a flow mapping (e.g., `{ key: }` or `{ key: oldvalue }`). It parses the content to find the colon and existing value, then constructs the new mapping string. Handles both cases: empty value after colon and existing value.

```rust
/// Handle value replacement within flow mappings more precisely
fn handle_flow_mapping_value_replacement(
    _content: &str,
    _start_byte: usize,
    _end_byte: usize,
    current_content: &str,
    value: &yaml_serde::Value,
) -> Result<String, Error> {
    let val_str = serialize_yaml_value(value)?;
    let val_str = val_str.trim();

    // Parse the flow mapping content to understand the structure
    let trimmed = current_content.trim();

    // Case 1: { key: } - has colon, empty value
    if let Some(colon_pos) = trimmed.find(':') {
        let before_colon = &trimmed[..colon_pos];
        let after_colon = &trimmed[colon_pos + 1..];

        // Check if there's already a value after the colon (excluding the closing brace)
        let value_part = after_colon.trim().trim_end_matches('}').trim();

        if value_part.is_empty() {
            // Case: { key: } -> { key: value }
            let key_part = before_colon.trim_start_matches('{').trim();
            Ok(format!("{{ {key_part}: {val_str} }}"))
        } else {
            // Case: { key: oldvalue } -> { key: newvalue }
            let key_part = before_colon.trim_start_matches('{').trim();
            Ok(format!("{{ {key_part}: {val_str} }}"))
        }
    } else {
        // Case 2: { key } - no colon, bare key -> { key: value }
        let key_part = trimmed.trim_start_matches('{').trim_end_matches('}').trim();
        Ok(format!("{{ {key_part}: {val_str} }}"))
    }
}
```

--------------------------------

### Handle non-empty block collection replacement

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Replaces a value in a block mapping when the new value is a non-empty collection (mapping or sequence). It emits the value as a nested block with 2-space indentation, preserving each line's relative depth. Empty collections remain inline.

```rust
        // A non-empty block collection can't share the key's line: splicing it
        // after `key:` produces invalid YAML even when its serialized form is a
        // single line, e.g. `target: outer: value` or `target: - value`. Emit it
        // as a nested block instead, while keeping empty collections inline.
        let is_nonempty_block_collection = match value {
            yaml_serde::Value::Mapping(mapping) => !mapping.is_empty(),
            yaml_serde::Value::Sequence(sequence) => !sequence.is_empty(),
            _ => false,
        };

        if is_nonempty_block_collection {
            let key_indent = &key_part[..key_part.len() - key_part.trim_start().len()];
            let mut result = key_part.to_string();
            for line in val_str.lines() {
                if !line.trim().is_empty() {
                    result.push('\n');
                    result.push_str(key_indent);
                    result.push_str("  "); // 2 spaces for nested content
                    // As above: preserve each line's own relative depth.
                    result.push_str(line);
                }
            }
            result
        } else {
            format!("{} {}", key_part, val_str.trim())
        }
    } else {
        // This is just a value, replace it directly

        serialize_yaml_value(value)?
    };

    Ok(replacement)
}
```

--------------------------------

### Rust: extract_leading_whitespace function

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Extracts leading spaces from the line containing a given YAML feature. Uses the document source and feature location to find the line span, then returns the whitespace prefix. Returns an empty string if the line has no leading spaces.

```rust
pub fn extract_leading_whitespace<'doc>(
    doc: &'doc yamlpath::Document,
    feature: &yamlpath::Feature,
) -> &'doc str {
    let line_range = line_span(doc, feature.location.byte_span.0);
    let line_content = &doc.source()[line_range];

    let end = line_content
        .bytes()
        .position(|b| b != b' ')
        .unwrap_or(line_content.len());

    &line_content[..end]
}
```

--------------------------------

### Patch Struct

Source: https://docs.rs/yamlpatch/latest/yamlpatch/struct.Patch.html

Represents a single YAML patch, consisting of a route to the feature to patch and the operation to perform.

```APIDOC
## Struct Patch

### Description
Represents a single YAML patch. A patch operation consists of a route to the feature to patch and the operation to perform on that feature.

### Definition
```rust
pub struct Patch<'doc> {
    pub route: Route<'doc>,
    pub operation: Op<'doc>,
}
```

### Fields
- **route** (`Route<'doc>`) - The route to the feature to patch.
- **operation** (`Op<'doc>`) - The operation to perform on the feature.

### Trait Implementations
- `Clone` - Provides `clone` and `clone_from` methods.
- `Debug` - Provides `fmt` method for formatting.

### Auto Trait Implementations
- `Freeze`
- `RefUnwindSafe`
- `Send`
- `Sync`
- `Unpin`
- `UnsafeUnpin`
- `UnwindSafe`

### Blanket Implementations
- `Any`, `Borrow`, `BorrowMut`, `CloneToUninit`, `From`, `Into`, `ToOwned`, `TryFrom`, `TryInto`

```

--------------------------------

### Op::RewriteFragment

Source: https://docs.rs/yamlpatch/latest/yamlpatch/enum.Op.html

Rewrites a fragment of a feature at the given path. This operation performs exactly one rewrite at a time, replacing the first match of `from` in the feature.

```APIDOC
## Op::RewriteFragment

### Description
Rewrites a fragment of a feature at the given path. This can be used to perform graceful rewrites of string values, regardless of their nested position or single/multi-line nature. This operation performs exactly one rewrite at a time, meaning that the first match of `from` in the feature will be replaced.

### Variant
`RewriteFragment { from: Subfeature<'doc>, to: Cow<'doc, str> }`

### Fields
- **from** (Subfeature<'doc>) - Required - The fragment to match and replace.
- **to** (Cow<'doc, str>) - Required - The replacement string.

### Notes
- The first match of `from` in the feature will be replaced.
- Can be made more precise by passing an `after` index, which specifies that the rewrite should only occur on the first match of `from` that occurs after the given byte index.

### Example
Given a feature with the value:

run: |
  echo "foo: ${{ foo }}"


It can be rewritten to:

run: |
  echo "foo ${FOO}"


via a `RewriteFragment` with:

route: "/run",
from: "${{ foo }}",
to: "${FOO}",

```

--------------------------------

### Style::from_feature

Source: https://docs.rs/yamlpatch/latest/yamlpatch/enum.Style.html

Determines the YAML style of a feature based on its document. This is a public method on the Style enum that takes a feature reference and its document, returning the corresponding Style variant.

```APIDOC
## Style::from_feature

### Description
Given a feature and its document, determine the style of the feature. This method inspects the YAML representation and returns the appropriate Style variant.

### Method
from_feature

### Signature
pub fn from_feature(feature: &Feature<'_>, doc: &Document) -> Self

### Parameters
- **feature** (&Feature<'_>) - Required - Reference to the feature whose style is to be determined.
- **doc** (&Document) - Required - Reference to the YAML document containing the feature.

### Returns
- **Style** - The style variant representing the YAML formatting of the feature.

### Example
```rust
let style = Style::from_feature(&feature, &doc);
```
```

--------------------------------

### EmplaceComment operation implementation

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Handles the Op::EmplaceComment operation. It checks for existing comments and either emplaces a new comment at the end of the first line of the feature, delegates to ReplaceComment if one comment exists, or errors on multiple comments. Includes FIXME notes about edge cases.

```rust
Op::EmplaceComment { new } => {
    // FIXME: We should gracefully handle empty features here,
    // since `foo:` -> `foo: # comment` is a reasonable operation.
    let feature = route_to_feature_exact(&patch.route, document)?.ok_or_else(|| {
        Error::InvalidOperation(format!(
            "no existing feature at {route:?}",
            route = patch.route
        ))
    })?;

    // FIXME: We can't emplace comments on non-block multi-line
    // scalars with the technique below, since the comment
    // would end up inside the scalar. We just exclude these for now.
    if matches!(
        Style::from_feature(&feature, document),
        Style::SingleQuoted | Style::DoubleQuoted
    ) && feature.is_multiline()
    {
        return Err(Error::InvalidOperation(format!(
            "cannot emplace comment on non-block multi-line scalar at {route:?}",
            route = patch.route
        )));
    }

    let comment_features = document.feature_comments(&feature);
    match comment_features.len() {
        0 => {
            // No existing comment; emplace a new one.
            // The 'right' emplacement location is subjective;
            // we capriciously choose to emplace the new comment at the end
            // of the first line of the feature.
            let line_range = line_span(document, feature.location.byte_span.0);
            let mut insert_pos = line_range.end;
            if let Some(b'\n') = document.source().as_bytes().get(insert_pos - 1) {
                insert_pos -= 1;
            }
            if let Some(b'\r') = document.source().as_bytes().get(insert_pos - 1) {
                insert_pos -= 1;
            }

            let mut result = content.to_string();
            result.insert_str(insert_pos, &format!(" {new}"));

            result
        }
        1 => {
            return apply_single_patch(
                document,
                &Patch {
                    route: patch.route.clone(),
                    operation: Op::ReplaceComment { new: new.clone() },
                },
            );
        }
        _ => {
            return Err(Error::InvalidOperation(format!(
                "multiple comments found at {route:?}",
                route = patch.route
            )));
        }
    }
}
```

--------------------------------

### extract_leading_indentation_for_block_item

Source: https://docs.rs/yamlpatch/latest/yamlpatch/fn.extract_leading_indentation_for_block_item.html

Extracts the number of leading spaces needed to align a block item with its surrounding context, accounting for block sequences.

```APIDOC
## Function extract_leading_indentation_for_block_item

### Description
Extracts the number of leading spaces needed to align a block item with its surrounding context. This takes into account block sequences, e.g. where the mapping is a child of a list item and needs to be properly aligned with the list item's other content.

### Signature
```rust
pub fn extract_leading_indentation_for_block_item(
    doc: &Document,
    feature: &Feature<'_>,
) -> usize
```

### Parameters
- **doc** (`&Document`) - The YAML document to inspect.
- **feature** (`&Feature<'_>`) - The feature for which to extract indentation.

### Returns
- **usize** - The number of leading spaces needed for alignment.
```

--------------------------------

### Finalize patched content

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Ensures the patched content ends with a newline and creates a new yamlpath::Document from it.

```rust
if !patched_content.ends_with('\n') {
    patched_content.push('\n');
}

yamlpath::Document::new(patched_content).map_err(Error::from)
```

--------------------------------

### ReplaceComment operation implementation

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Handles the Op::ReplaceComment operation. It finds the exact feature at the patch route, retrieves its comment features, and replaces the comment. Returns an error if no feature exists or if multiple comments are found.

```rust
Op::ReplaceComment { new } => {
    let feature = route_to_feature_exact(&patch.route, document)?.ok_or_else(|| {
        Error::InvalidOperation(format!(
            "no existing feature at {route:?}",
            route = patch.route
        ))
    })?;

    let comment_features = document.feature_comments(&feature);
    let comment_feature = match comment_features.len() {
        0 => return Ok(document.clone()),
        1 => &comment_features[0],
        _ => {
            return Err(Error::InvalidOperation(format!(
                "multiple comments found at {route:?}",
                route = patch.route
            )));
        }
    };

    let mut result = content.to_string();
    result.replace_range(comment_feature, new);

    result
}
```

--------------------------------

### Style enum definition

Source: https://docs.rs/yamlpatch/latest/yamlpatch/enum.Style.html

The Style enum definition with all its variants, representing different YAML styles.

```rust
pub enum Style {
    BlockMapping,
    BlockSequence,
    MultilineFlowMapping,
    FlowMapping,
    MultilineFlowSequence,
    FlowSequence,
    MultilineLiteralScalar,
    MultilineFoldedScalar,
    DoubleQuoted,
    SingleQuoted,
    PlainScalar,
}
```

--------------------------------

### route_to_feature_exact

Source: https://docs.rs/yamlpatch/latest/yamlpatch/fn.route_to_feature_exact.html

Resolves a route to a feature in a YAML document, returning an optional Feature reference. This function is part of the yamlpatch crate's public API.

```APIDOC
## Function route_to_feature_exact

### Description
Resolves a route to a feature in a YAML document, returning an optional Feature reference. This function is part of the yamlpatch crate's public API.

### Signature
```rust
pub fn route_to_feature_exact<'a>(
    route: &Route<'_>,
    doc: &'a Document,
) -> Result<Option<Feature<'a>>, Error>
```

### Parameters
- **route** (`&Route<'_>`) - Required - The route to resolve.
- **doc** (`&'a Document`) - Required - The YAML document to search.

### Returns
- **`Result<Option<Feature<'a>>, Error>`** - Returns `Ok(Some(feature))` if the route resolves to a feature, `Ok(None)` if no feature is found, or `Err(Error)` on failure.
```

--------------------------------

### Op::ReplaceComment

Source: https://docs.rs/yamlpatch/latest/yamlpatch/enum.Op.html

Replaces the entire comment associated with the feature at the given path with the new comment. Only one matching comment is permitted; features without a comment are ignored, and features with multiple comments are rejected.

```APIDOC
## Op::ReplaceComment

### Description
Replaces the entire comment associated with the feature at the given path with the new comment. The entire comment is replaced at once, and only one matching comment is permitted. Features that don't have an associated comment are ignored, while features with multiple comments will be rejected.

### Variant
`ReplaceComment { new: Cow<'doc, str> }`

### Fields
- **new** (Cow<'doc, str>) - Required - The new comment to replace the existing one.

### Notes
- Only one matching comment is permitted.
- Features without a comment are ignored.
- Features with multiple comments are rejected.
```

--------------------------------

### Append operation

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Implements the Append operation, which appends a value to a sequence. It checks the style of the sequence (block vs flow) and returns an error for flow sequences or non-sequence routes. For block sequences, it replaces the content in the document.

```rust
Op::Append { value } => {
    let feature = route_to_feature_exact(&patch.route, document)?.ok_or_else(|| {
        Error::InvalidOperation(format!(
            "no existing sequence at {route:?}",
            route = patch.route
        ))
    })?;

    let style = Style::from_feature(&feature, document);

    match style {
        Style::BlockSequence => {
            let updated_feature = handle_block_sequence_append(document, &feature, value)?;

            // Replace the content in the document
            let mut result = content.to_string();
            result.replace_range(&feature, &updated_feature);

            result
        }
        Style::FlowSequence => {
            return Err(Error::InvalidOperation(format!(
                "append operation is not permitted against flow sequence route: {:?}",
                patch.route
            )));
        }
        _ => {
            return Err(Error::InvalidOperation(format!(
                "append operation is only permitted against sequence routes: {:?}",
                patch.route
            )));
        }
    }
}
```

--------------------------------

### Op::EmplaceComment

Source: https://docs.rs/yamlpatch/latest/yamlpatch/enum.Op.html

Emplaces a comment at the given path. This is like `ReplaceComment`, but will insert a new comment if none exists.

```APIDOC
## Op::EmplaceComment

### Description
Emplaces a comment at the given path. This is like `ReplaceComment`, but will insert a new comment if none exists.

### Variant
`EmplaceComment { new: Cow<'doc, str> }`

### Fields
- **new** (Cow<'doc, str>) - Required - The comment to emplace.

### Notes
- If no comment exists, a new one is inserted.
```

--------------------------------

### Remove operation

Source: https://docs.rs/yamlpatch/latest/src/yamlpatch/lib.rs.html

Implements the Remove operation, which deletes a value from the document. It returns an error if the route is empty (cannot remove root), otherwise computes the byte span to delete and removes it from the content string.

```rust
Op::Remove => {
    if patch.route.is_empty() {
        return Err(Error::InvalidOperation(
            "Cannot remove root document".to_string(),
        ));
    }

    // Delegate to `yamlpath`, which computes the precise byte span
    // to delete based on the value's  container kind.
    let span = document.removal_span(&patch.route)?;

    let mut result = content.to_string();
    result.replace_range(span, "");

    result
}
```

--------------------------------

### extract_leading_whitespace

Source: https://docs.rs/yamlpatch/latest/yamlpatch/fn.extract_leading_whitespace.html

Extracts leading whitespace from the beginning of the line containing the given feature.

```APIDOC
## Function extract_leading_whitespace

### Description
Extracts leading whitespace from the beginning of the line containing the given feature.

### Signature
```rust
pub fn extract_leading_whitespace<'doc>(
    doc: &'doc Document,
    feature: &Feature<'_>,
) -> &'doc str
```

### Parameters
- **doc** (`&'doc Document`) - The YAML document to search.
- **feature** (`&Feature<'_>`) - The feature whose line's leading whitespace is to be extracted.

### Return Value
- `&'doc str` - The leading whitespace of the line containing the feature.

```

=== COMPLETE CONTENT === This response contains all available snippets from this library. No additional content exists. Do not make further requests.