Accept --columns as a JSON array.

Promote NuGet to 0.1.21

LinuxPackage.nuspec

@@ -2,14 +2,14 @@
 <package >
   <metadata>
     <id>pq2json_linux</id>
-    <version>0.1.20</version>
+    <version>0.1.21</version>
     <authors>Evgeney Ryzhyk</authors>
     <owners>Evgeney Ryzhyk</owners>
     <license type="expression">MIT</license>
     <projectUrl>https://github.com/Azure/azure-kusto-parquet-conv</projectUrl>
     <requireLicenseAcceptance>false</requireLicenseAcceptance>
     <description>Parquet to JSON (line delimited) converter tool.</description>
-    <releaseNotes>Updated Rust dependencies for security fixes.</releaseNotes>
+    <releaseNotes>Accept --columns as a JSON array.</releaseNotes>
     <copyright>Copyright 2020</copyright>
     <tags></tags>
     <dependencies></dependencies>

Package.nuspec

@@ -2,14 +2,14 @@
 <package >
   <metadata>
     <id>pq2json</id>
-    <version>0.1.20</version>
+    <version>0.1.21</version>
     <authors>Evgeney Ryzhyk</authors>
     <owners>Evgeney Ryzhyk</owners>
     <license type="expression">MIT</license>
     <projectUrl>https://github.com/Azure/azure-kusto-parquet-conv</projectUrl>
     <requireLicenseAcceptance>false</requireLicenseAcceptance>
     <description>Parquet to JSON (line delimited) converter tool.</description>
-    <releaseNotes>Updated Rust dependencies for security fixes.</releaseNotes>
+    <releaseNotes>Accept --columns as a JSON array.</releaseNotes>
     <copyright>Copyright 2020</copyright>
     <tags></tags>
     <dependencies></dependencies>

pq2json/src/main.rs

@@ -139,9 +139,10 @@ fn main() {
         timestamp_rendering,
         omit_empty_lists: matches.is_present("omit-empty-lists") || matches.is_present("prune"),
         convert_types: matches.is_present("convert-types"),
-        columns: matches
-            .value_of("columns")
-            .map(|columns| columns.split(",").map(|s| s.to_string()).collect()),
+        columns: matches.value_of("columns").map(|columns| {
+            serde_json::from_str::<Vec<String>>(columns)
+                .expect("Expected a well-formed JSON array of column names, each surrounded by escaped double-quotes")
+        }),
         csv: matches.is_present("csv"),
     };