Struct Expression

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pub struct Expression { /* private fields */ }

Expand description

An SPDX license expression that is both syntactically and semantically valid, and can be evaluated

use spdx::Expression;

let this_is_fine = Expression::parse("MIT OR Apache-2.0").unwrap();
assert!(this_is_fine.evaluate(|req| {
    if let spdx::LicenseItem::Spdx { id, .. } = req.license {
        // Both MIT and Apache-2.0 are OSI approved, so this expression
        // evaluates to true
        return id.is_osi_approved();
    }

   false
}));

assert!(!this_is_fine.evaluate(|req| {
    if let spdx::LicenseItem::Spdx { id, .. } = req.license {
        // This is saying we don't accept any licenses that are OSI approved
        // so the expression will evaluate to false as both sides of the OR
        // are now rejected
        return !id.is_osi_approved();
    }

    false
}));

// `NOPE` is not a valid SPDX license identifier, so this expression
// will fail to parse
let _this_is_not = Expression::parse("MIT OR NOPE").unwrap_err();

Implementations§

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impl Expression

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pub fn minimized_requirements<'lic>( &self, accepted: impl IntoIterator<Item = &'lic Licensee>, ) -> Result<Vec<LicenseReq>, MinimizeError>

Given a set of Licensees, attempts to find the minimum number that satisfy this Expression.

The list of licensees should be given in priority order, eg, if you wish to accept the Apache-2.0 license if it is available, and the MIT if not, putting Apache-2.0 before MIT will cause the ubiquitous Apache-2.0 OR MIT expression to minimize to just Apache-2.0 as only 1 of the licenses is required, and Apache-2.0 has priority.

§Errors

This method will fail if more than 64 unique licensees are satisfied by this expression, but such a case is unlikely in a real world scenario. The list of licensees must also actually satisfy this expression, otherwise it can’t be minimized.

§Example

let expr = spdx::Expression::parse("Apache-2.0 OR MIT").unwrap();

let apache_licensee = spdx::Licensee::parse("Apache-2.0").unwrap();
assert_eq!(
    expr.minimized_requirements([&apache_licensee, &spdx::Licensee::parse("MIT").unwrap()]).unwrap(),
    vec![apache_licensee.into_req()],
);

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impl Expression

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pub fn parse(original: &str) -> Result<Self, ParseError>

Given a license expression, attempts to parse and validate it as a valid SPDX expression. Uses ParseMode::Strict.

The validation can fail for many reasons:

The expression contains invalid characters
An unknown/invalid license or exception identifier was found. Only SPDX short identifiers are allowed
The expression contained unbalanced parentheses
A license or exception immediately follows another license or exception, without a valid AND, OR, or WITH operator separating them
An AND, OR, or WITH doesn’t have a license or ) preceding it

spdx::Expression::parse("MIT OR Apache-2.0 WITH LLVM-exception").unwrap();

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pub fn canonicalize(original: &str) -> Result<Option<String>, ParseError>

Canonicalizes the input expression into a form that can be parsed with ParseMode::STRICT

§Transforms

‘/’ is replaced with ’ OR ’
Lower-cased operators (‘or’, ‘and’, ‘with’) are upper-cased
‘+’ is transformed to -or-later for GNU licenses, or -only with no ‘+’
Invalid/imprecise license identifiers (eg. apache2) are replaced with their valid identifiers

If the provided expression is not modified then None is returned

Note that this only does fixup of otherwise valid expressions, passing the resulting string to Expression::parse can still result in additional parse errors, eg. unbalanced parentheses

let expr = "apache with LLVM-exception/gpl-3.0+ and gplv2";
assert_eq!(
    spdx::Expression::canonicalize(expr).unwrap().unwrap(),
    "Apache-2.0 WITH LLVM-exception OR GPL-3.0-or-later AND GPL-2.0-only"
);

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pub fn parse_mode(original: &str, mode: ParseMode) -> Result<Self, ParseError>

Parses an expression with the specified ParseMode.

With ParseMode::Lax it permits some non-SPDX syntax, such as imprecise license names and “/” used instead of “OR” in expressions.

spdx::Expression::parse_mode(
    "mit/Apache-2.0 WITH LLVM-exception",
    spdx::ParseMode::LAX
).unwrap();

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impl Expression

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pub fn requirements(&self) -> impl Iterator<Item = &ExpressionReq>

Returns each of the license requirements in the license expression, but not the operators that join them together

let expr = spdx::Expression::parse("MIT AND BSD-2-Clause").unwrap();

assert_eq!(
    &expr.requirements().map(|er| er.req.license.id()).collect::<Vec<_>>(), &[
        spdx::license_id("MIT"),
        spdx::license_id("BSD-2-Clause")
    ]
);

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pub fn iter(&self) -> impl Iterator<Item = &ExprNode>

Returns both the license requirements and the operators that join them together. Note that the expression is returned in post fix order.

use spdx::expression::{ExprNode, Operator};
let expr = spdx::Expression::parse("Apache-2.0 OR MIT").unwrap();

let mut ei = expr.iter();

assert!(ei.next().is_some()); // Apache
assert!(ei.next().is_some()); // MIT
assert_eq!(*ei.next().unwrap(), ExprNode::Op(Operator::Or));

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pub fn evaluate<AF: FnMut(&LicenseReq) -> bool>(&self, allow_func: AF) -> bool

Evaluates the expression, using the provided function to determine if the licensee meets the requirements for each license term. If enough requirements are satisfied the evaluation will return true.

use spdx::Expression;

let this_is_fine = Expression::parse("MIT OR Apache-2.0").unwrap();
assert!(this_is_fine.evaluate(|req| {
    // If we find MIT, then we're happy!
    req.license.id() == spdx::license_id("MIT")
}));

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