Struct HunkApplier 

pub struct HunkApplier<'a> { /* private fields */ }

An iterator that applies hunks from a patch one by one.

This struct provides fine-grained control over the patch application process. It allows you to apply hunks sequentially, inspect the intermediate state of the content, and handle results on a per-hunk basis.

The iterator yields a HunkApplyStatus for each hunk in the patch.

Example

use mpatch::{parse_single_patch, HunkApplier, HunkApplyStatus, ApplyOptions};

// 1. Define original content and a patch.
let original_lines = vec!["line 1", "line 2", "line 3"];
let diff_content = r#"
```diff
--- a/file.txt
+++ b/file.txt
@@ -2,1 +2,1 @@
-line 2
+line two
```
"#;
let patch = parse_single_patch(diff_content)?;
let options = ApplyOptions::new();

// 2. Create the applier.
let mut applier = HunkApplier::new(&patch, Some(&original_lines), &options);

// 3. Apply the first (and only) hunk.
let status = applier.next().unwrap();
assert!(matches!(status, HunkApplyStatus::Applied { .. }));

// 4. Check that there are no more hunks.
assert!(applier.next().is_none());

// 5. Finalize the content.
let new_content = applier.into_content();
assert_eq!(new_content, "line 1\nline two\nline 3\n");

Implementations

impl<'a> HunkApplier<'a>

pub fn new<T: AsRef<str>>( patch: &'a Patch, original_lines: Option<&'a [T]>, options: &'a ApplyOptions, ) -> Self

Creates a new HunkApplier to begin a step-by-step patch operation.

This constructor initializes the applier with the patch to be applied and the original content. The content is provided as an optional slice of lines, allowing for both file modifications (Some(lines)) and file creations (None). The applier can then be used as an iterator to apply hunks one by one.

Example

let original_lines = vec!["line 1", "line 2"];
let diff = "```diff\n--- a/f\n+++ b/f\n@@ -2,1 +2,1\n-line 2\n+line two\n```";
let patch = parse_single_patch(diff)?;
let options = ApplyOptions::new();

// Create the applier for a step-by-step operation.
let mut applier = HunkApplier::new(&patch, Some(&original_lines), &options);

// Now `applier` is ready to be used as an iterator.
let status = applier.next().unwrap();

pub fn current_lines(&self) -> &[String]

Returns a slice of the current lines, reflecting all hunks applied so far.

This method provides read-only access to the intermediate state of the content being patched. It is useful for inspecting the content between applying hunks with the HunkApplier iterator.

Example

let original_lines = vec!["line 1", "line 2"];
let diff = "```diff\n--- a/f\n+++ b/f\n@@ -2,1 +2,1\n-line 2\n+line two\n```";
let patch = parse_single_patch(diff)?;
let options = ApplyOptions::new();

let mut applier = HunkApplier::new(&patch, Some(&original_lines), &options);

// Before applying, it's the original content.
assert_eq!(applier.current_lines(), &["line 1", "line 2"]);

// Apply the hunk.
applier.next();

// After applying, the lines are updated.
assert_eq!(applier.current_lines(), &["line 1", "line two"]);

pub fn set_original_newline_status(&mut self, ends_with_newline: bool)

Sets whether the original content ended with a newline.

When working with a slice of lines (e.g., Vec<String>), the information about whether the original file ended with a newline character is typically lost. This method allows you to restore that context.

mpatch uses this information to determine the newline status of the final output:

1. If a patch modifies the end of the file (i.e., the last hunk applies to the very end), the patch’s ends_with_newline setting takes precedence.
2. If the patch only modifies the middle of the file, the original newline status is preserved.

By default, HunkApplier assumes the original content ended with a newline (true).

Arguments

• ends_with_newline - true if the original content had a trailing newline, false otherwise.

Example

// Original content: "line 1\nline 2" (No trailing newline)
let original_lines = vec!["line 1", "line 2"];
let diff = "```diff\n--- a/f\n+++ b/f\n@@ -1,1 +1,1\n-line 1\n+line one\n```";
let patch = parse_single_patch(diff)?;
let options = ApplyOptions::new();

let mut applier = HunkApplier::new(&patch, Some(&original_lines), &options);

// Crucial step: Tell the applier the original file didn't have a newline.
applier.set_original_newline_status(false);

applier.next(); // Apply the hunk (modifies line 1)

// The result should preserve the "no newline" status because the patch didn't touch EOF.
let result = applier.into_content();
assert_eq!(result, "line one\nline 2");

pub fn into_lines(self) -> Vec<String>

Consumes the applier and returns the final vector of lines.

After iterating through the HunkApplier and applying all desired hunks, this method can be called to take ownership of the final, modified vector of strings.

Example

let original_lines = vec!["line 1", "line 2"];
let diff = "```diff\n--- a/f\n+++ b/f\n@@ -2,1 +2,1\n-line 2\n+line two\n```";
let patch = parse_single_patch(diff)?;
let options = ApplyOptions::new();

let mut applier = HunkApplier::new(&patch, Some(&original_lines), &options);
applier.next(); // Apply all hunks

let final_lines = applier.into_lines();
assert_eq!(final_lines, vec!["line 1".to_string(), "line two".to_string()]);

pub fn into_content(self) -> String

Consumes the applier and returns the final content as a single string.

This method joins the final lines with newlines and ensures the content has a trailing newline if required by the patch’s ends_with_newline property. It is the most common way to get the final result from a HunkApplier.

Example

let original_lines = vec!["line 1"];
let diff = "```diff\n--- a/f\n+++ b/f\n@@ -1,1 +1,1\n-line 1\n+line one\n```";
let patch = parse_single_patch(diff)?;
let options = ApplyOptions::new();

let mut applier = HunkApplier::new(&patch, Some(&original_lines), &options);
applier.next(); // Apply all hunks

let final_content = applier.into_content();
assert_eq!(final_content, "line one\n");

Trait Implementations

impl<'a> Debug for HunkApplier<'a>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a> Iterator for HunkApplier<'a>

fn next(&mut self) -> Option<Self::Item>

Applies the next hunk in the patch and returns its status.

This method advances the iterator, applying one hunk to the internal state of the HunkApplier. It returns Some(HunkApplyStatus) for each hunk in the patch, and None when all hunks have been processed.

Example

let original_lines = vec!["line 1", "line 2"];
let diff = "```diff\n--- a/f\n+++ b/f\n@@ -2,1 +2,1\n-line 2\n+line two\n```";
let patch = parse_single_patch(diff)?;
let options = ApplyOptions::new();

let mut applier = HunkApplier::new(&patch, Some(&original_lines), &options);

// Call next() to apply the first hunk.
let status = applier.next();
assert!(matches!(status, Some(HunkApplyStatus::Applied { .. })));

// Call next() again; there are no more hunks.
assert!(applier.next().is_none());

type Item = HunkApplyStatus

The type of the elements being iterated over.

fn next_chunk<const N: usize>( &mut self, ) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>

where Self: Sized,

🔬This is a nightly-only experimental API. (iter_next_chunk)

Advances the iterator and returns an array containing the next N values.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the iterator.

fn count(self) -> usize

where Self: Sized,

Consumes the iterator, counting the number of iterations and returning it.

fn last(self) -> Option<Self::Item>

where Self: Sized,

Consumes the iterator, returning the last element.

fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>>

🔬This is a nightly-only experimental API. (iter_advance_by)

Advances the iterator by n elements.

fn nth(&mut self, n: usize) -> Option<Self::Item>

Returns the nth element of the iterator.

fn step_by(self, step: usize) -> StepBy<Self>

where Self: Sized,

Creates an iterator starting at the same point, but stepping by the given amount at each iteration.

fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter>

where Self: Sized, U: IntoIterator<Item = Self::Item>,

Takes two iterators and creates a new iterator over both in sequence.

fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter>

where Self: Sized, U: IntoIterator,

‘Zips up’ two iterators into a single iterator of pairs.

fn intersperse(self, separator: Self::Item) -> Intersperse<Self>

where Self: Sized, Self::Item: Clone,

🔬This is a nightly-only experimental API. (iter_intersperse)

Creates a new iterator which places a copy of separator between items of the original iterator.

fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G>

where Self: Sized, G: FnMut() -> Self::Item,

🔬This is a nightly-only experimental API. (iter_intersperse)

Creates a new iterator which places an item generated by separator between items of the original iterator.

fn map<B, F>(self, f: F) -> Map<Self, F>

where Self: Sized, F: FnMut(Self::Item) -> B,

Takes a closure and creates an iterator which calls that closure on each element.

fn for_each<F>(self, f: F)

where Self: Sized, F: FnMut(Self::Item),

Calls a closure on each element of an iterator.

fn filter<P>(self, predicate: P) -> Filter<Self, P>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator which uses a closure to determine if an element should be yielded.

fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F>

where Self: Sized, F: FnMut(Self::Item) -> Option<B>,

Creates an iterator that both filters and maps.

fn enumerate(self) -> Enumerate<Self>

where Self: Sized,

Creates an iterator which gives the current iteration count as well as the next value.

fn peekable(self) -> Peekable<Self>

where Self: Sized,

Creates an iterator which can use the peek and peek_mut methods to look at the next element of the iterator without consuming it. See their documentation for more information.

fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator that skips elements based on a predicate.

fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator that yields elements based on a predicate.

fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P>

where Self: Sized, P: FnMut(Self::Item) -> Option<B>,

Creates an iterator that both yields elements based on a predicate and maps.

fn skip(self, n: usize) -> Skip<Self>

where Self: Sized,

Creates an iterator that skips the first n elements.

fn take(self, n: usize) -> Take<Self>

where Self: Sized,

Creates an iterator that yields the first n elements, or fewer if the underlying iterator ends sooner.

fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F>

where Self: Sized, F: FnMut(&mut St, Self::Item) -> Option<B>,

An iterator adapter which, like fold, holds internal state, but unlike fold, produces a new iterator.

fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F>

where Self: Sized, U: IntoIterator, F: FnMut(Self::Item) -> U,

Creates an iterator that works like map, but flattens nested structure.

fn map_windows<F, R, const N: usize>(self, f: F) -> MapWindows<Self, F, N>

where Self: Sized, F: FnMut(&[Self::Item; N]) -> R,

🔬This is a nightly-only experimental API. (iter_map_windows)

Calls the given function f for each contiguous window of size N over self and returns an iterator over the outputs of f. Like slice::windows(), the windows during mapping overlap as well.

fn fuse(self) -> Fuse<Self>

where Self: Sized,

Creates an iterator which ends after the first None.

fn inspect<F>(self, f: F) -> Inspect<Self, F>

where Self: Sized, F: FnMut(&Self::Item),

Does something with each element of an iterator, passing the value on.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Iterator.

fn collect<B>(self) -> B

where B: FromIterator<Self::Item>, Self: Sized,

Transforms an iterator into a collection.

fn collect_into<E>(self, collection: &mut E) -> &mut E

where E: Extend<Self::Item>, Self: Sized,

🔬This is a nightly-only experimental API. (iter_collect_into)

Collects all the items from an iterator into a collection.

fn partition<B, F>(self, f: F) -> (B, B)

where Self: Sized, B: Default + Extend<Self::Item>, F: FnMut(&Self::Item) -> bool,

Consumes an iterator, creating two collections from it.

fn is_partitioned<P>(self, predicate: P) -> bool

where Self: Sized, P: FnMut(Self::Item) -> bool,

🔬This is a nightly-only experimental API. (iter_is_partitioned)

Checks if the elements of this iterator are partitioned according to the given predicate, such that all those that return true precede all those that return false.

fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R

where Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Output = B>,

An iterator method that applies a function as long as it returns successfully, producing a single, final value.

fn try_for_each<F, R>(&mut self, f: F) -> R

where Self: Sized, F: FnMut(Self::Item) -> R, R: Try<Output = ()>,

An iterator method that applies a fallible function to each item in the iterator, stopping at the first error and returning that error.

fn fold<B, F>(self, init: B, f: F) -> B

where Self: Sized, F: FnMut(B, Self::Item) -> B,

Folds every element into an accumulator by applying an operation, returning the final result.

fn reduce<F>(self, f: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(Self::Item, Self::Item) -> Self::Item,

Reduces the elements to a single one, by repeatedly applying a reducing operation.

fn try_reduce<R>( &mut self, f: impl FnMut(Self::Item, Self::Item) -> R, ) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType

where Self: Sized, R: Try<Output = Self::Item>, <R as Try>::Residual: Residual<Option<Self::Item>>,

🔬This is a nightly-only experimental API. (iterator_try_reduce)

Reduces the elements to a single one by repeatedly applying a reducing operation. If the closure returns a failure, the failure is propagated back to the caller immediately.

fn all<F>(&mut self, f: F) -> bool

where Self: Sized, F: FnMut(Self::Item) -> bool,

Tests if every element of the iterator matches a predicate.

fn any<F>(&mut self, f: F) -> bool

where Self: Sized, F: FnMut(Self::Item) -> bool,

Tests if any element of the iterator matches a predicate.

fn find<P>(&mut self, predicate: P) -> Option<Self::Item>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Searches for an element of an iterator that satisfies a predicate.

fn find_map<B, F>(&mut self, f: F) -> Option<B>

where Self: Sized, F: FnMut(Self::Item) -> Option<B>,

Applies function to the elements of iterator and returns the first non-none result.

fn try_find<R>( &mut self, f: impl FnMut(&Self::Item) -> R, ) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType

where Self: Sized, R: Try<Output = bool>, <R as Try>::Residual: Residual<Option<Self::Item>>,

🔬This is a nightly-only experimental API. (try_find)

Applies function to the elements of iterator and returns the first true result or the first error.

fn position<P>(&mut self, predicate: P) -> Option<usize>

where Self: Sized, P: FnMut(Self::Item) -> bool,

Searches for an element in an iterator, returning its index.

fn max_by_key<B, F>(self, f: F) -> Option<Self::Item>

where B: Ord, Self: Sized, F: FnMut(&Self::Item) -> B,

Returns the element that gives the maximum value from the specified function.

fn max_by<F>(self, compare: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,

Returns the element that gives the maximum value with respect to the specified comparison function.

fn min_by_key<B, F>(self, f: F) -> Option<Self::Item>

where B: Ord, Self: Sized, F: FnMut(&Self::Item) -> B,

Returns the element that gives the minimum value from the specified function.

fn min_by<F>(self, compare: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,

Returns the element that gives the minimum value with respect to the specified comparison function.

fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB)

where FromA: Default + Extend<A>, FromB: Default + Extend<B>, Self: Sized + Iterator<Item = (A, B)>,

Converts an iterator of pairs into a pair of containers.

fn copied<'a, T>(self) -> Copied<Self>

where T: Copy + 'a, Self: Sized + Iterator<Item = &'a T>,

Creates an iterator which copies all of its elements.

fn cloned<'a, T>(self) -> Cloned<Self>

where T: Clone + 'a, Self: Sized + Iterator<Item = &'a T>,

Creates an iterator which clones all of its elements.

fn array_chunks<const N: usize>(self) -> ArrayChunks<Self, N>

where Self: Sized,

🔬This is a nightly-only experimental API. (iter_array_chunks)

Returns an iterator over N elements of the iterator at a time.

fn sum<S>(self) -> S

where Self: Sized, S: Sum<Self::Item>,

Sums the elements of an iterator.

fn product<P>(self) -> P

where Self: Sized, P: Product<Self::Item>,

Iterates over the entire iterator, multiplying all the elements

fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering

where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Ordering,

🔬This is a nightly-only experimental API. (iter_order_by)

Lexicographically compares the elements of this Iterator with those of another with respect to the specified comparison function.

fn partial_cmp<I>(self, other: I) -> Option<Ordering>

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Lexicographically compares the PartialOrd elements of this Iterator with those of another. The comparison works like short-circuit evaluation, returning a result without comparing the remaining elements. As soon as an order can be determined, the evaluation stops and a result is returned.

fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering>

where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,

🔬This is a nightly-only experimental API. (iter_order_by)

Lexicographically compares the elements of this Iterator with those of another with respect to the specified comparison function.

fn eq<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialEq<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are equal to those of another.

fn eq_by<I, F>(self, other: I, eq: F) -> bool

where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, <I as IntoIterator>::Item) -> bool,

🔬This is a nightly-only experimental API. (iter_order_by)

Determines if the elements of this Iterator are equal to those of another with respect to the specified equality function.

fn ne<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialEq<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are not equal to those of another.

fn lt<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically less than those of another.

fn le<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically less or equal to those of another.

fn gt<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically greater than those of another.

fn ge<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically greater than or equal to those of another.

fn is_sorted_by<F>(self, compare: F) -> bool

where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> bool,

Checks if the elements of this iterator are sorted using the given comparator function.

fn is_sorted_by_key<F, K>(self, f: F) -> bool

where Self: Sized, F: FnMut(Self::Item) -> K, K: PartialOrd,

Checks if the elements of this iterator are sorted using the given key extraction function.