Merge pull request #2356 from dathere/template-globals-json-option

`template`: add `--globals-json` option

src/cmd/template.rs

@@ -74,6 +74,10 @@ template arguments:
 template options:
     --template <str>            MiniJinja template string to use (alternative to --template-file)
     -t, --template-file <file>  MiniJinja template file to use
+    -j, --globals-json <file>   A JSON file containing global variables to make available in templates.
+                                The JSON properties can be accessed in templates using the "globals"
+                                namespace (e.g. {{globals.school_name}}, {{globals.year}}).
+                                This allows sharing common values across all template renders.
     --outfilename <str>         MiniJinja template string to use to create the filename of the output 
                                 files to write to <outdir>. If set to just QSV_ROWNO, the filestem
                                 is set to the current rowno of the record, padded with leading
@@ -116,6 +120,7 @@ Common options:
 use std::{
     fs,
     io::{BufWriter, Write},
+    path::PathBuf,
     sync::{
         atomic::{AtomicBool, AtomicU16, Ordering},
         OnceLock, RwLock,
@@ -131,7 +136,7 @@ use rayon::{
     prelude::IntoParallelRefIterator,
 };
 use serde::Deserialize;
-use simd_json::BorrowedValue;
+use simd_json::{json, BorrowedValue};
 
 use crate::{
     config::{Config, Delimiter, DEFAULT_WTR_BUFFER_CAPACITY},
@@ -148,6 +153,7 @@ struct Args {
     arg_outdir:              Option<String>,
     flag_template:           Option<String>,
     flag_template_file:      Option<String>,
+    flag_globals_json:       Option<PathBuf>,
     flag_output:             Option<String>,
     flag_outfilename:        String,
     flag_outsubdir_size:     u16,
@@ -218,6 +224,23 @@ pub fn run(argv: &[&str]) -> CliResult<()> {
         Ordering::Relaxed,
     );
 
+    // setup globals JSON context if specified
+    let mut globals_flag = false;
+    let globals_ctx = if let Some(globals_json) = args.flag_globals_json {
+        globals_flag = true;
+        match std::fs::read(globals_json) {
+            Ok(mut bytes) => match simd_json::from_slice(&mut bytes) {
+                Ok(json) => json,
+                Err(e) => return fail_clierror!("Failed to parse globals JSON file: {e}"),
+            },
+            Err(e) => return fail_clierror!("Failed to read globals JSON file: {e}"),
+        }
+    } else {
+        json!("")
+    };
+
+    let globals_ctx_borrowed: simd_json::BorrowedValue = globals_ctx.into();
+
     // Set up minijinja environment
     let mut env = Environment::new();
 
@@ -255,7 +278,7 @@ pub fn run(argv: &[&str]) -> CliResult<()> {
     }
     let width = rowcount.to_string().len();
 
-    // read headers
+    // read headers - the headers are used as MiniJinja variables in the template
     let headers = if args.flag_no_headers {
         csv::StringRecord::new()
     } else {
@@ -427,6 +450,13 @@ pub fn run(argv: &[&str]) -> CliResult<()> {
                 let curr_record = record;
 
                 let mut context = simd_json::borrowed::Object::default();
+                // Add globals context to the record context
+                if globals_flag {
+                    context.insert(
+                        std::borrow::Cow::Borrowed("globals"),
+                        globals_ctx_borrowed.clone(),
+                    );
+                }
                 context.reserve(headers_len);
                 let mut row_number = 0_u64;
 
@@ -452,7 +482,7 @@ pub fn run(argv: &[&str]) -> CliResult<()> {
                         }
                     }
                 } else {
-                    // Use header names
+                    // Use header names as template variables
                     for (header, field) in headers.iter().zip(curr_record.iter()) {
                         context.insert(
                             std::borrow::Cow::Borrowed(header),

tests/test_template.rs

@@ -1113,3 +1113,78 @@ fn template_round_banker_filter() {
     );
     assert_eq!(got, expected);
 }
+
+#[test]
+fn template_globals_json() {
+    let wrk = Workdir::new("template_globals");
+    wrk.create(
+        "data.csv",
+        vec![
+            svec!["name", "score"],
+            svec!["Alice", "85"],
+            svec!["Bob", "92"],
+        ],
+    );
+
+    wrk.create_from_string(
+        "globals.json",
+        r#"{
+            "passing_score": 90,
+            "school_name": "Test Academy",
+            "year": 2023
+        }"#,
+    );
+
+    let mut cmd = wrk.command("template");
+    cmd.arg("--template")
+        .arg(concat!(
+            "School: {{globals.school_name}}\n",
+            "Year: {{globals.year}}\n",
+            "Student: {{name}}\n",
+            "Score: {{score}}\n",
+            "Status: {% if score|int >= globals.passing_score %}PASS{% else %}FAIL{% endif \
+             %}\n\n\n"
+        ))
+        .arg("--globals-json")
+        .arg("globals.json")
+        .arg("data.csv");
+
+    let got: String = wrk.stdout(&mut cmd);
+    let expected = concat!(
+        "School: Test Academy\n",
+        "Year: 2023\n",
+        "Student: Alice\n",
+        "Score: 85\n",
+        "Status: FAIL\n\n",
+        "School: Test Academy\n",
+        "Year: 2023\n",
+        "Student: Bob\n",
+        "Score: 92\n",
+        "Status: PASS"
+    );
+    assert_eq!(got, expected);
+}
+
+#[test]
+fn template_globals_json_invalid() {
+    let wrk = Workdir::new("template_globals_invalid");
+    wrk.create("data.csv", vec![svec!["name"], svec!["test"]]);
+
+    wrk.create_from_string(
+        "invalid.json",
+        r#"{
+            "bad_json": "missing_comma"
+            "another_field": true
+        }"#,
+    );
+
+    let mut cmd = wrk.command("template");
+    cmd.arg("--template")
+        .arg("{{name}}\n")
+        .arg("--globals-json")
+        .arg("invalid.json")
+        .arg("data.csv");
+
+    let got: String = wrk.output_stderr(&mut cmd);
+    assert!(got.contains("Failed to parse globals JSON file"));
+}