chore(enterprise): Extend library functionality for secret scanning (vectordotdev#17483)

Ref OPB-710

This PR
- Exposes patterns and the `interpolate` function for use in OPW. This
will help deduplicate some logic and reduce maintenance burden. We use
the patterns themselves in secret scanning logic, and will use the
`interpolate` function in bootstrap-related logic.

Author: wbew

src/config/loading/secret.rs

@@ -26,7 +26,7 @@ use crate::{
 // - "SECRET[backend..secret.name]" will match and capture "backend" and ".secret.name"
 // - "SECRET[secret_name]" will not match
 // - "SECRET[.secret.name]" will not match
-static COLLECTOR: Lazy<Regex> =
+pub static COLLECTOR: Lazy<Regex> =
     Lazy::new(|| Regex::new(r"SECRET\[([[:word:]]+)\.([[:word:].]+)\]").unwrap());
 
 /// Helper type for specifically deserializing secrets backends.

src/config/mod.rs

@@ -48,7 +48,8 @@ pub use format::{Format, FormatHint};
 pub use id::{ComponentKey, Inputs};
 pub use loading::{
     load, load_builder_from_paths, load_from_paths, load_from_paths_with_provider_and_secrets,
-    load_from_str, load_source_from_paths, merge_path_lists, process_paths, CONFIG_PATHS,
+    load_from_str, load_source_from_paths, merge_path_lists, process_paths, COLLECTOR,
+    CONFIG_PATHS,
 };
 pub use provider::ProviderConfig;
 pub use secret::SecretBackend;
@@ -59,6 +60,7 @@ pub use transform::{
 };
 pub use unit_test::{build_unit_tests, build_unit_tests_main, UnitTestResult};
 pub use validation::warnings;
+pub use vars::{interpolate, ENVIRONMENT_VARIABLE_INTERPOLATION_REGEX};
 pub use vector_core::config::{
     init_log_schema, log_schema, proxy::ProxyConfig, LogSchema, OutputId,
 };

src/config/vars.rs

@@ -1,7 +1,25 @@
 use std::collections::HashMap;
 
+use once_cell::sync::Lazy;
 use regex::{Captures, Regex};
 
+// Environment variable names can have any characters from the Portable Character Set other
+// than NUL.  However, for Vector's interpolation, we are closer to what a shell supports which
+// is solely of uppercase letters, digits, and the '_' (that is, the `[:word:]` regex class).
+// In addition to these characters, we allow `.` as this commonly appears in environment
+// variable names when they come from a Java properties file.
+//
+// https://pubs.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap08.html
+pub static ENVIRONMENT_VARIABLE_INTERPOLATION_REGEX: Lazy<Regex> = Lazy::new(|| {
+    Regex::new(
+        r"(?x)
+        \$\$|
+        \$([[:word:].]+)|
+        \$\{([[:word:].]+)(?:(:?-|:?\?)([^}]*))?\}",
+    )
+    .unwrap()
+});
+
 /// (result, warnings)
 pub fn interpolate(
     input: &str,
@@ -10,22 +28,7 @@ pub fn interpolate(
     let mut errors = Vec::new();
     let mut warnings = Vec::new();
 
-    // Environment variable names can have any characters from the Portable Character Set other
-    // than NUL.  However, for Vector's interpolation, we are closer to what a shell supports which
-    // is solely of uppercase letters, digits, and the '_' (that is, the `[:word:]` regex class).
-    // In addition to these characters, we allow `.` as this commonly appears in environment
-    // variable names when they come from a Java properties file.
-    //
-    // https://pubs.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap08.html
-    let re = Regex::new(
-        r"(?x)
-        \$\$|
-        \$([[:word:].]+)|
-        \$\{([[:word:].]+)(?:(:?-|:?\?)([^}]*))?\}",
-    )
-    .unwrap();
-
-    let interpolated = re
+    let interpolated = ENVIRONMENT_VARIABLE_INTERPOLATION_REGEX
         .replace_all(input, |caps: &Captures<'_>| {
             let flags = caps.get(3).map(|m| m.as_str()).unwrap_or_default();
             let def_or_err = caps.get(4).map(|m| m.as_str()).unwrap_or_default();