wax 0.4.0

Opinionated and portable globs that can be matched against paths and directory trees.

Wax is a Rust library that provides opinionated and portable globs that can be matched against file paths and directory trees. Globs use a familiar syntax and support expressive features with semantics that emphasize component boundaries.

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Basic Usage

Match a path against a glob:

use wax::{Glob, Pattern};

let glob = Glob::new("*.png").unwrap();

Match a path against a glob with matched text (captures):

use wax::{CandidatePath, Glob, Pattern};

let glob = Glob::new("**/{*.{go,rs}}").unwrap();

let path = CandidatePath::from("src/main.go");
let matched = glob.matched(&path).unwrap();

assert_eq!("main.go", matched.get(2).unwrap());

Match files in a directory tree against a glob:

use wax::Glob;

let glob = Glob::new("**/*.{md,txt}").unwrap();
for entry in glob.walk("doc", usize::MAX) {
    let entry = entry.unwrap();
    // ...

Match a path against multiple globs:

use wax::{Glob, Pattern};

let any = wax::any::<Glob, _>([

See more details below.


Globs are encoded as UTF-8 strings called glob expressions that resemble Unix paths consisting of nominal components delimited by separators. Wax exposes most of its APIs via the Glob type, which is constructed from a glob expression via inherent functions or standard conversion traits. All data is borrowed where possible but can be copied into owned instances using an into_owned method with most types.

use wax::Glob;

let glob = Glob::new("site/img/logo.svg").unwrap();

Regardless of platform or operating system, globs always use the same format and are distinct from paths. In particular, forward slash / is always the path separator and back slashes \ are forbidden (back slash is used for escape sequences, but the literal sequence \\ is not supported). This means that it is impossible to represent \ in nominal path components, but this character is generally forbidden as such and its disuse avoids confusion.

Globs enforce various rules regarding meta-characters, patterns, and component boundaries (separators and tree wildcards) that reject nonsense expressions.


Globs resemble Unix paths, but additionally support patterns that can be matched against paths and directory trees. Patterns use a syntax that resembles globbing in Unix shells and tools like git, though there are some important differences.

use wax::Glob;

let glob = Glob::new("**/*.{go,rs}").unwrap();

Patterns form captures that can be used to extract matched text (as seen in many regular expression engines). In the above example, there are three patterns that can be queried for matched text: **/, *, and {go,rs}.

Globs use a consistent and opinionated format and patterns are not configurable; the semantics of a particular glob are always the same. For example, * never matches across component boundaries.


Wildcards match some amount of arbitrary text in paths and are the most fundamental pattern provided by globs (and likely the most familiar).

The zero-or-more wildcards * and $ match zero or more of any character except path separators. Zero-or-more wildcards cannot be adjacent to other zero-or-more wildcards. The * wildcard is eager and will match the longest possible text while the $ wildcard is lazy and will match the shortest possible text. When followed by a literal, * stops at the last occurrence of that literal while $ stops at the first occurence.

The exactly-one wildcard ? matches any single character except path separators. Exactly-one wildcards do not group automatically, so a pattern of contiguous wildcards such as ??? form distinct captures for each ? wildcard. An alternative can be used to group exactly-one wildcards into a single capture, such as {???}.

The tree wildcard ** matches zero or more components (directories). This is the only pattern that implicitly matches across arbitrary component boundaries; all other patterns do not implicitly match across component (directory) boundaries. When a tree wildcard participates in a match and does not terminate the pattern, its captured text includes the trailing separator. If a tree wildcard does not participate in a match, then its captured text is an empty string. Tree wildcards must be delimited by forward slashes or terminations (such as the beginning and/or end of a glob or sub-glob). Tree wildcards and path separators are distinct and any adjacent forward slashes that form a tree wildcard are parsed together (but rooting forward slashes are still meaningful). If a glob expression consists solely of a tree wildcard, then it matches any and all files and directory trees.

Character Classes

Character classes match any single character from a group of literals and ranges except path separators. Classes are delimited by square brackets [...]. Individual character literals are specified as is, such as [ab] to match either a or b. Character ranges are formed from two characters separated by a hyphen, such as [x-z] to match x, y, or z. Note that character classes match exact characters and are always case-sensitive, so the expressions [ab] and {a,b} are not necessarily the same.

Any number of character literals and ranges can be used within a single character class. For example, [qa-cX-Z] matches any of q, a, b, c, X, Y, or Z.

Character classes may be negated by including an exclamation mark ! at the beginning of the class pattern. For example, [!a] matches any character except for a. These are the only patterns that support negation.

It is possible to escape meta-characters like *, $, etc., using character classes though globs also support escaping via a backslash \. To match the control characters [, ], and - within a character class, they must be escaped via a backslash, such as [a\-] to match a or -.

Character classes have notable platform-specific behavior, because they match arbitrary characters in native paths but never match path separators. This means that if a character class only matches path separators on a given platform, then the character class is considered empty and matches nothing. For example, in the expression a[/]b the character class [/] matches nothing on Unix and Windows. Such character classes are not rejected, because the role of arbitrary characters depends on the platform. In practice, this is rarely a concern, but such patterns should be avoided.

Character classes have limited utility on their own, but compose well with repetitions.


Alternatives match an arbitrary sequence of one or more comma separated sub-globs delimited by curly braces {...,...}. For example, {a?c,x?z,foo} matches any of the sub-globs a?c, x?z, or foo. Alternatives may be arbitrarily nested and composed with repetitions.

Alternatives form a single capture group regardless of the contents of their sub-globs. This capture is formed from the complete match of the sub-glob, so if the sub-glob a?c matches abc in {a?c,x?z}, then the captured text will be abc (not b as it would be outside of an alternative sequence). Alternatives can be used to group captures using a single sub-glob, such as {*.{go,rs}} to capture an entire file name with a particular extension or {???} to group a sequence of exactly-one wildcards.

Alternatives must consider adjacency rules and neighboring patterns. For example, *{a,b*} is allowed but *{a,*b} is not. Additionally, they may not contain a sub-glob consisting of a singular tree wildcard ** and cannot root a glob expression as this could cause the expression to match or walk overlapping trees.


Repetitions match a sub-glob a specified number of times and more closely resemble general purpose regular expressions. Repetitions are delimited by angle brackets with a separating colon <...:...> where a sub-glob precedes the colon and a bounds specification follows it. For example, <a*/:0,> matches the sub-glob a*/ zero or more times. Though not implicit like tree wildcards, repetitions can match across component boundaries (and can themselves include tree wildcards). Repetitions may be arbitrarily nested and composed with alternatives.

Bound specifications are formed from inclusive lower and upper bounds separated by a comma ,, such as :1,4 to match between one and four times. The upper bound is optional and may be omitted. For example, :1, matches one or more times (note the trailing comma ,). A singular bound is convergent, so :3 matches exactly three times (both the lower and upper bounds are three). If no lower or upper bound is specified, then the sub-glob matches one or more times, so <a:> and <a:1,> are equivalent. Similarly, if the colon : is also omitted, then the sub-glob matches zero or more times, so <a> and <a:0,> are equivalent.

Repetitions form a singular capture group regardless of the contents of their sub-glob. The capture is formed from the complete match of the sub-glob. If the repetition <abc/> matches abc/abc/, then the captured text will be abc/abc/.

Repetitions compose well with character classes. Most often, a glob expression like {????} is sufficient, but the more specific expression <[0-9]:4> further constrains the matched characters to digits, for example. Repetitions may also be more terse, such as <?:4>. Furthermore, repetitions can form tree expressions that further constrain directories, such as <[!.]*/>[!.]* to match paths that contain no leading dots ..

Repetitions must consider adjacency rules and neighboring patterns. For example, a/<b/**:1,> is allowed but <a/**:1,>/b is not. Additionally, they may not contain a sub-glob consisting of a singular separator /, a singular zero-or-more wildcard * or $, nor a singular tree wildcard **. Repetitions with a lower bound of zero may not root a glob expression, as this could cause the expression to match or walk overlapping trees.


Glob patterns can be combined and matched together using the any combinator. any accepts an IntoIterator type with items that can be converted into a type that implements Pattern (most notably Glob). The output is an Any, which implements Pattern and efficiently matches any of its input patterns. This is often more ergonomic and faster than matching against multiple Globs.

use wax::{Glob, Pattern};

let any = wax::any::<Glob, _>(["**/*.txt", "src/**/*.rs"]).unwrap();

The first type parameter determines to which Pattern type the input items are converted and is typically Glob.

Because any accepts any types that can be converted into a Pattern type, it is possible to combine opaque patterns from foreign code (i.e., Globs obtained from functions in external crates).

extern crate foreign;

use wax::{Glob, Pattern};

let theirs: Glob = foreign::get().unwrap();
let mine = Glob::new("**/*.txt").unwrap();

if wax::any::<Glob, _>([theirs, mine]).unwrap().is_match("src/README.txt") {
    // ...

Unlike alternatives, Any supports patterns with overlapping trees (rooted and unrooted expressions). However, it is not possible to match an Any against a directory tree (as with Glob::walk).

Flags and Case Sensitivity

Flags toggle the matching behavior of globs. Importantly, flags are a part of a glob expression rather than an API. Behaviors are toggled immediately following flags in the order in which they appear in glob expressions. Flags are delimited by parenthesis with a leading question mark (?...) and may appear anywhere within a glob expression so long as they do not split tree wildcards (e.g., a/*(?i)* is not allowed). Each flag is represented by a single character and can be negated by preceding the corresponding character with a minus -. Flags are toggled in the order in which they appear within (?...).

The only supported flag is the case-insensitivty flag i. By default, glob expressions use the same case sensitivity as the target platforms's file system APIs (case-sensitive on Unix and case-insensitive on Windows), but i can be used to toggle this explicitly as needed. For example, (?-i)photos/**/*.(?i){jpg,jpeg} matches file paths beneath a photos directory with a case-sensitive base and a case-insensitive extension jpg or jpeg.

Wax considers literals, their configured case sensitivity, and the case sensitivity of the target platform's file system when partitioning glob expressions with Glob::partitioned. Partitioning is unaffected in glob expressions with no flags.

Errors and Diagnostics

The GlobError type represents error conditions that can occur when parsing a glob expression, validating a glob expression, or walking a directory tree with a glob. GlobError and its sub-errors implement the standard Error and Display traits via thiserror, which express basic information about failures.

Wax optionally integrates with the miette crate, which can be used to capture and display diagnostics. This can be useful for reporting errors to users that provide glob expressions. Diagnostic reporting, including warnings and help diagnostics, can be enabled with the diagnostics-report feature.

Error: glob::rule

  x malformed glob expression: adjacent zero-or-more wildcards `*` or `$`
 1 | doc/**/*{.md,.tex,*.txt}
   :        |^^^^^^^^|^^^^^^^
   :        |        | `-- here
   :        |        `-- in this alternative
   :        `-- here

Wax also provides inspection APIs that allow code to query glob metadata. Diagnostic inspection can be enabled with the diagnostics-inspect feature.

use wax::Glob;

let glob = Glob::new("videos/**/{*.{mp4,webm}}").unwrap();
assert_eq!(2, glob.captures().count());

Diagnostics are disabled by default and can be enabled with the diagnostics meta-feature, which enables both the diagnostics-inspect and diagnostics-report features. This can be done via Cargo in a crate's Cargo.toml file.

version = "^0.0.0"
features = ["diagnostics"]

Unsupported Path Features

Any components not recognized as separators nor patterns are interpreted as literals. In combination with strict rules, this means some platform-specific path features cannot be used directly in globs. This limitation is by design and additional code may be necessary to bridge this gap for some use cases.

Partitioning and Semantic Literals

Globs support no notion of a current or parent directory. The path components . and .. are interpreted as literals and only match paths with the corresponding components (even on Unix and Windows). For example, the glob src/../*.rs matches the path src/../lib.rs but does not match the path lib.rs.

Parent directory components have unclear meaning and far less utility when they follow patterns in a glob. However, such components are intuitive and are often important for escaping a working directory when they precede patterns (i.e., as a prefix). For example, the glob ../src/**/*.rs has more obvious meaning than the glob src/**/../*.rs. As seen above though, the first glob would only match the literal path component .. and not paths that replace this with a parent directory.

Glob::partitioned can be used to parse glob expressions that contain semantic components that precede patterns and would be interpreted as literals (namely ..). Glob::partitioned partitions a glob expression into an invariant PathBuf prefix and a variant Glob postfix. Here, invariant means that the partition contains no glob patterns and resolves the same literal paths on the target platform's file system. The prefix can be used as needed in combination with the glob.

use std::path::Path;
use wax::Glob;

let path = Path::new("."); // Working directory.
let (prefix, glob) = Glob::partitioned("../site/img/*.{jpg,png}").unwrap();
for entry in glob.walk(path.join(prefix), usize::MAX) {
    let entry = entry.unwrap();
    // ...

Additionally, Glob::has_semantic_literals can be used to detect literal components in a glob that have special semantics on the target platform.

use wax::Glob;

let glob = Glob::new("../**/src/**/main.rs").unwrap();

Schemes and Prefixes

While globs can be rooted, they cannot include schemes nor Windows path prefixes. For example, the Windows UNC share path \\server\share\src cannot be represented directly as a glob.

This can be limiting, but the design of Wax explicitly forbids this: Windows prefixes and other volume components are not portable. Instead, when this is needed, an additional native path or working directory can be used, such as the --tree option provided by Nym. In most contexts, globs are applied relative to some such working directory.


Globs operate exclusively on UTF-8 encoded text. However, this encoding is not used for file names and paths on all platforms. Wax uses the CandidatePath type to re-encode native paths via lossy conversions that use Unicode replacement codepoints whenever a part of a path cannot be represented as valid UTF-8. On some platforms these conversions are always no-ops. In practice, most paths can be losslessly encoded in UTF-8, but this means that Wax cannot match some byte sequences.


At the time of writing, Wax is experimental and unstable. It is possible that glob expression syntax and semantics may change between versions in the 0.y.z series without warning nor deprecation.