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i/prompting: implement path pattern matching and validation
Path pattern matching is implemented via the doublestar package, which
emulates bash's globstar matching. Patterns may include '*' wildcard
characters (which match any number of non-separator characters), '**'
doublestars (which match zero or more subdirectories), '?' wildcard
characters (which match exactly one non-separator character), and nested
groups delimited by '{' and '}'. Notably, path patterns are *not* allowed
to have character classes delimited by '[' and ']', nor inverted
classes of the form "[^abc]".
There is a limit on the number of groups allowed in path patterns, but
up to that limit, groups may be arbitrarily nested or sequential.
Signed-off-by: Oliver Calder <oliver.calder@canonical.com>
i/prompting: fix typo and add notes to remove test boilerplate
Signed-off-by: Oliver Calder <oliver.calder@canonical.com>
i/prompting: use separate test suite for patterns
Signed-off-by: Oliver Calder <oliver.calder@canonical.com>
i/prompting: improve unit test coverage
Signed-off-by: Oliver Calder <oliver.calder@canonical.com>- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,116 @@ | ||
| // -*- Mode: Go; indent-tabs-mode: t -*- | ||
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| /* | ||
| * Copyright (C) 2024 Canonical Ltd | ||
| * | ||
| * This program is free software: you can redistribute it and/or modify | ||
| * it under the terms of the GNU General Public License version 3 as | ||
| * published by the Free Software Foundation. | ||
| * | ||
| * This program is distributed in the hope that it will be useful, | ||
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| * GNU General Public License for more details. | ||
| * | ||
| * You should have received a copy of the GNU General Public License | ||
| * along with this program. If not, see <http://www.gnu.org/licenses/>. | ||
| * | ||
| */ | ||
|
|
||
| package prompting | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "strings" | ||
|
|
||
| doublestar "github.com/bmatcuk/doublestar/v4" | ||
| ) | ||
|
|
||
| // Limit the number of groups which are allowed to occur in a pattern. | ||
| // This number includes all groups, including those nested or in series. | ||
| const maxGroupsInPattern = 10 | ||
|
|
||
| // ValidatePathPattern returns nil if the pattern is valid, otherwise an error. | ||
| func ValidatePathPattern(pattern string) error { | ||
| if pattern == "" || pattern[0] != '/' { | ||
| return fmt.Errorf("invalid path pattern: must start with '/': %q", pattern) | ||
| } | ||
| depth := 0 | ||
| totalGroups := 0 | ||
| reader := strings.NewReader(pattern) | ||
| for { | ||
| r, _, err := reader.ReadRune() | ||
| if err != nil { | ||
| // No more runes | ||
| break | ||
| } | ||
| switch r { | ||
| case '{': | ||
| depth += 1 | ||
| totalGroups += 1 | ||
| if totalGroups > maxGroupsInPattern { | ||
| return fmt.Errorf("invalid path pattern: exceeded maximum number of groups (%d): %q", maxGroupsInPattern, pattern) | ||
| } | ||
| case '}': | ||
| depth -= 1 | ||
| if depth < 0 { | ||
| return fmt.Errorf("invalid path pattern: unmatched '}' character: %q", pattern) | ||
| } | ||
| case '\\': | ||
| // Skip next rune | ||
| _, _, err = reader.ReadRune() | ||
| if err != nil { | ||
| return fmt.Errorf(`invalid path pattern: trailing unescaped '\' character: %q`, pattern) | ||
| } | ||
| case '[', ']': | ||
| return fmt.Errorf("invalid path pattern: cannot contain unescaped '[' or ']': %q", pattern) | ||
| } | ||
| } | ||
| if depth != 0 { | ||
| return fmt.Errorf("invalid path pattern: unmatched '{' character: %q", pattern) | ||
| } | ||
| if !doublestar.ValidatePattern(pattern) { | ||
| return fmt.Errorf("invalid path pattern: %q", pattern) | ||
| } | ||
| return nil | ||
| } | ||
|
|
||
| // PathPatternMatch returns true if the given pattern matches the given path. | ||
| // | ||
| // The pattern should not contain groups, and should likely have been an output | ||
| // of ExpandPathPattern. | ||
| // | ||
| // Paths to directories are received with trailing slashes, but we don't want | ||
| // to require the user to include a trailing '/' if they want to match | ||
| // directories (and end their pattern with `{,/}` if they want to match both | ||
| // directories and non-directories). Thus, we want to ensure that patterns | ||
| // without trailing slashes match paths with trailing slashes. However, | ||
| // patterns with trailing slashes should not match paths without trailing | ||
| // slashes. | ||
| // | ||
| // The doublestar package has special cases for patterns ending in `/**` and | ||
| // `/**/`: `/foo/**`, and `/foo/**/` both match `/foo` and `/foo/`. We want to | ||
| // override this behavior to make `/foo/**/` not match `/foo`. We also want to | ||
| // override doublestar to make `/foo` match `/foo/`. | ||
| func PathPatternMatch(pattern string, path string) (bool, error) { | ||
| // Check the usual doublestar match first, in case the pattern is malformed | ||
| // and causes an error, and return the error if so. | ||
| matched, err := doublestar.Match(pattern, path) | ||
| if err != nil { | ||
| return false, err | ||
| } | ||
| // No matter if doublestar matched, return false if pattern ends in '/' but | ||
| // path is not a directory. | ||
| if strings.HasSuffix(pattern, "/") && !strings.HasSuffix(path, "/") { | ||
| return false, nil | ||
| } | ||
| if matched { | ||
| return true, nil | ||
| } | ||
| if strings.HasSuffix(pattern, "/") { | ||
| return false, nil | ||
| } | ||
| // Try again with a '/' appended to the pattern, so patterns like `/foo` | ||
| // match paths like `/foo/`. | ||
| return doublestar.Match(pattern+"/", path) | ||
| } |
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