Updating doc for release

usage/csv-tsv.md

@@ -1,4 +1,33 @@
-# Working with CSV, TSV
+# CSV
+Encode/Decode/Roundtrip CSV and TSV files.
+
+## Encode 
+Currently supports arrays of homogenous flat objects, that is: no nesting and it assumes the _first_ object has all the keys required:
+
+```yaml
+- name: Bobo
+  type: dog
+- name: Fifi
+  type: cat
+```
+
+As well as arrays of arrays of scalars (strings/numbers/booleans):
+
+```yaml
+- [Bobo, dog]
+- [Fifi, cat]
+```
+
+## Decode
+Decode assumes the first CSV/TSV row is the header row, and all rows beneath are the entries.
+The data will be coded into an array of objects, using the header rows as keys.
+
+```csv
+name,type
+Bobo,dog
+Fifi,cat
+```
+
 
 {% hint style="warning" %}
 Note that versions prior to 4.18 require the 'eval/e' command to be specified. 
@@ -6,71 +35,180 @@ Note that versions prior to 4.18 require the 'eval/e' command to be specified.&#
 `yq e <exp> <file>`
 {% endhint %}
 
-## Yaml to CSV/TSV
-
-You can convert compatible yaml structures to CSV or TSV by using:
-
-* `--output-format=csv` or `-o=c` for csv (comma separated values)
-* `--output-format=tsv` or `-o=t` for tsv (tab separated values)
-
-Compatible structures is either an array of scalars (strings/numbers/booleans), which is a single row; or an array of arrays of scalars (multiple rows).
-
+## Encode CSV simple
+Given a sample.yml file of:
 ```yaml
 - [i, like, csv]
 - [because, excel, is, cool]
 ```
-
 then
-
 ```bash
-yq '.' -o=csv sample.yaml
+yq -o=csv sample.yml
 ```
-
-will output:
-
+will output
 ```csv
 i,like,csv
 because,excel,is,cool
 ```
 
-Similarly, for tsv:
-
+## Encode TSV simple
+Given a sample.yml file of:
+```yaml
+- [i, like, csv]
+- [because, excel, is, cool]
+```
+then
 ```bash
-yq '.' -o=tsv sample.yaml
-```
-
-will output:
-
+yq -o=tsv sample.yml
 ```
+will output
+```tsv
 i	like	csv
 because	excel	is	cool
 ```
 
-### Converting an array of objects to CSV
-
-If you have a yaml document like:
-
+## Encode array of objects to csv
+Given a sample.yml file of:
 ```yaml
-foo: bar
-items:
-  - name: Tom
-    species: cat
-    color: blue
-  - name: Jim
-    species: dog
-    color: brown
+- name: Gary
+  numberOfCats: 1
+  likesApples: true
+  height: 168.8
+- name: Samantha's Rabbit
+  numberOfCats: 2
+  likesApples: false
+  height: -188.8
+
 ```
-
-To convert to CSV, you need to transform this into a array of CSV rows. Assuming you also want a header, then you can do:
-
+then
 ```bash
-yq '[["name", "species", "color"]] + [.items[] | [.name, .species, .color]]' data.yaml -o=csv
+yq -o=csv sample.yml
 ```
-
-to yield:
-
+will output
 ```csv
-name,species,color
-Tom,cat,blue
-Jim,dog,brown
+name,numberOfCats,likesApples,height
+Gary,1,true,168.8
+Samantha's Rabbit,2,false,-188.8
 ```
+
+## Encode array of objects to custom csv format
+Add the header row manually, then the we convert each object into an array of values - resulting in an array of arrays. Pick the columns and call the header whatever you like.
+
+Given a sample.yml file of:
+```yaml
+- name: Gary
+  numberOfCats: 1
+  likesApples: true
+  height: 168.8
+- name: Samantha's Rabbit
+  numberOfCats: 2
+  likesApples: false
+  height: -188.8
+
+```
+then
+```bash
+yq -o=csv '[["Name", "Number of Cats"]] +  [.[] | [.name, .numberOfCats ]]' sample.yml
+```
+will output
+```csv
+Name,Number of Cats
+Gary,1
+Samantha's Rabbit,2
+```
+
+## Encode array of objects to csv - missing fields behaviour
+First entry is used to determine the headers, and it is missing 'likesApples', so it is not included in the csv. Second entry does not have 'numberOfCats' so that is blank
+
+Given a sample.yml file of:
+```yaml
+- name: Gary
+  numberOfCats: 1
+  height: 168.8
+- name: Samantha's Rabbit
+  height: -188.8
+  likesApples: false
+
+```
+then
+```bash
+yq -o=csv sample.yml
+```
+will output
+```csv
+name,numberOfCats,height
+Gary,1,168.8
+Samantha's Rabbit,,-188.8
+```
+
+## Parse CSV into an array of objects
+First row is assumed to be the header row.
+
+Given a sample.csv file of:
+```csv
+name,numberOfCats,likesApples,height
+Gary,1,true,168.8
+Samantha's Rabbit,2,false,-188.8
+
+```
+then
+```bash
+yq -p=csv sample.csv
+```
+will output
+```yaml
+- name: Gary
+  numberOfCats: 1
+  likesApples: true
+  height: 168.8
+- name: Samantha's Rabbit
+  numberOfCats: 2
+  likesApples: false
+  height: -188.8
+```
+
+## Parse TSV into an array of objects
+First row is assumed to be the header row.
+
+Given a sample.tsv file of:
+```tsv
+name	numberOfCats	likesApples	height
+Gary	1	true	168.8
+Samantha's Rabbit	2	false	-188.8
+
+```
+then
+```bash
+yq -p=tsv sample.tsv
+```
+will output
+```yaml
+- name: Gary
+  numberOfCats: 1
+  likesApples: true
+  height: 168.8
+- name: Samantha's Rabbit
+  numberOfCats: 2
+  likesApples: false
+  height: -188.8
+```
+
+## Round trip
+Given a sample.csv file of:
+```csv
+name,numberOfCats,likesApples,height
+Gary,1,true,168.8
+Samantha's Rabbit,2,false,-188.8
+
+```
+then
+```bash
+yq -p=csv -o=csv '(.[] | select(.name == "Gary") | .numberOfCats) = 3' sample.csv
+```
+will output
+```csv
+name,numberOfCats,likesApples,height
+Gary,3,true,168.8
+Samantha's Rabbit,2,false,-188.8
+```
+